CBSE Class 7 Science All Chapters Worksheet

Question I. (i) The earliest methods of measuring time were based on ______________ of events.
Answer: periodic
In simple words: Ancient time measurement relied on recurring natural events like day and night or phases of the moon.

Exam Tip: Remember that 'periodic' refers to events that repeat at regular intervals.

Question I. (ii) ______________, ______________ and ______________ were the main methods in early time to measure the time.
Answer: Sundial, Water clock, Sand clock
In simple words: Early devices used shadows, flowing water, or falling sand to track the passage of time.

Exam Tip: Memorize these three traditional devices as classic examples of early time-measuring instruments.

Question I. (iii) There are ________seconds in an hour.
Answer: 3600
In simple words: One hour equals 60 minutes, and each minute has 60 seconds, so \(60 \times 60 = 3600\).

Exam Tip: Always show the conversion explicitly: \(1 \text{ hour} = 60 \text{ minutes} = 60 \times 60 \text{ seconds} = 3600 \text{ seconds}\).

Question I. (iv) We use the idea of speed to distinguish between ______________ and ______________ objects.
Answer: fast, slow
In simple words: Speed tells us how quickly or slowly an object covers distance.

Exam Tip: Speed is defined as the distance covered by a body in unit time.

Question I. (v) SI unit of speed is _______& of time is_______.
Answer: m/s, second
In simple words: The standard international units for speed and time are meters per second and seconds.

Exam Tip: Always include standard units in numerical answers to avoid losing marks.

Question I. (vi) The graph plotted between distance and time for the uniform motion is always in ______________.
Answer: a straight line
In simple words: Equal distances covered in equal intervals of time form a straight line on a distance-time graph.

Exam Tip: A curved line on a distance-time graph represents non-uniform motion.

Question I. (vii) ___________clock is the most accurate clock.
Answer: Quartz
In simple words: Modern electronic clocks using quartz crystals measure time with extreme precision.

Exam Tip: Mention quartz or atomic clocks as the most precise instruments for timekeeping.

Question I. (viii) 1 Km/ hr = ________m/ sec.
Answer: \(\frac{5}{18}\)
In simple words: To convert kilometers per hour into meters per second, multiply by \(\frac{5}{18}\).

Exam Tip: \(1 \text{ km/hr} = \frac{1000 \text{ m}}{3600 \text{ s}} = \frac{5}{18} \text{ m/s}\).

Question II. (i) In non-uniform motion, the speed of an object changes for every equal intervals of time.
Answer: True
In simple words: Non-uniform motion means changing speeds over equal time intervals.

Exam Tip: Understand that varying speed results in unequal distances covered in equal time spans.

Question II. (ii) Time = \(\frac{\text{Distance}}{\text{Speed}}\)
Answer: True
In simple words: Time is calculated by dividing distance by speed.

Question II. (iii) Cars always move with uniform motion.
Answer: False
In simple words: Cars speed up and slow down in traffic, making their motion non-uniform.

Exam Tip: Perfectly uniform motion is rare in daily practical scenarios.

Question II. (iv) Time period of a pendulum depends on the weight of the bob.
Answer: False
In simple words: The time period of a simple pendulum depends solely on its length, not the mass or weight of the bob.

Question II. (v) Motion of pendulum is non uniform motion.
Answer: False
In simple words: The motion of a simple pendulum is periodic and oscillatory, not simply classified as non-uniform in the general sense.

Exam Tip: Classify pendulum motion specifically as periodic or oscillatory.

Question III. (i) The resting position of the bob of pendulum.
Answer: Mean position
In simple words: The central stationary point of a pendulum is its mean position.

Exam Tip: Use exact scientific terminology like 'mean position'.

Question III. (ii) Device fixed in vehicles which shows its speed.
Answer: Speedometer
In simple words: The dashboard instrument measuring instantaneous speed is the speedometer.

Question III. (iii) Time taken for pendulum to complete one oscillation.
Answer: Time period
In simple words: One complete swing back and forth defines the time period.

Exam Tip: SI unit of time period is second.

Question III. (iv) Total distance covered by body in unit time.
Answer: Speed
In simple words: Distance traveled per unit time is speed.

Question III. (v) To & fro motion of the bob about its mean position.
Answer: Oscillatory motion
In simple words: Repetitive back and forth movement is called oscillation.

Exam Tip: Oscillatory motion is a special type of periodic motion.

MODULE – 7

Question I. (i) Give one-one example of Uniform and Non uniform motion
Answer: Uniform motion: A car moving at a constant speed of 60 km/h on a straight highway.
Non-uniform motion: A bus moving through crowded city traffic.
In simple words: Uniform covers equal distances in equal times; non-uniform does not.

Exam Tip: Always cite real-life scenarios for clarity.

Question I. (ii) Give one-one example of Periodic & Non periodic motion
Answer: Periodic motion: The motion of the hands of a clock.
Non-periodic motion: A child running randomly in a park.
In simple words: Periodic motion repeats at regular intervals of time.

Question I. (iii) Give one-one example of Oscillatory motion
Answer: The motion of a simple pendulum.
In simple words: Back and forth periodic motion is oscillatory.

Exam Tip: All oscillatory motions are periodic, but not all periodic motions are oscillatory.

Question II. (i) Plot the graph for: A body at rest.
Answer:

In simple words: A body at rest shows a horizontal line parallel to the time axis because distance does not change with time.

Exam Tip: A zero slope on a distance-time graph signifies zero speed (rest).

Question II. (ii) Plot the graph for: A bus moving with uniform speed.
Answer:

In simple words: Uniform speed is represented by a straight diagonal line rising steadily.

Exam Tip: The slope of a distance-time graph gives the speed of the object.

Question II. (iii) Plot the graph for: If a body covers unequal distances in equal interval of time.
Answer:

In simple words: Non-uniform motion produces a curved line on a distance-time graph.

Exam Tip: Whenever speed varies, the graph turns into a curve.

QUESTION BANK

Question I. (i) Define: Rest
Answer: A body is said to be at rest if it does not change its position with respect to its surroundings with the passage of time.
In simple words: An object that stays in the same place is at rest.

Exam Tip: Always mention 'with respect to surroundings' in definitions of rest and motion.

Question I. (ii) Define: Motion
Answer: A body is said to be in motion if it changes its position or direction with respect to its surroundings with the passage of time.
In simple words: An object that changes its location over time is in motion.

Exam Tip: Change in position is the core criterion for motion.

Question I. (iii) Define: Uniform motion
Answer: When an object covers equal distances in equal intervals of time, it is said to be moving with constant speed or in uniform motion.
In simple words: Moving at a steady, unchanging speed.

Exam Tip: Highlight 'equal distances in equal intervals of time'.

Question I. (iv) Define: Non-uniform motion
Answer: If a body covers unequal distances in equal intervals of time, it is said to be in non-uniform motion.
In simple words: Speed changes continuously during travel.

Exam Tip: Contrast this with uniform motion for clarity in exams.

Question II. What is speed? What is its SI unit?
Answer: The distance covered by a body in a unit time is called speed. Its SI unit is meters per second (m/s).
In simple words: Speed measures how fast an object moves.

Exam Tip: Formula: \(\text{Speed} = \frac{\text{Distance}}{\text{Time}}\).

Question III. Calculate the speed of body which covers a distance of 900 km in 5 hrs.
Answer:
Distance = 900 km
Time = 5 hours
\(\text{Speed} = \frac{\text{Distance}}{\text{Time}}\)
\(\text{Speed} = \frac{900}{5} = 180 \text{ km/hr}\)
In simple words: Divide total distance by total time to get speed.

Exam Tip: Always write given values, formula, and final answer with correct units.

Question IV. (i) Convert: 50 m/s into km/h
Answer:
\(50 \text{ m/s} = 50 \times \frac{18}{5} \text{ km/h}\)
\(= 10 \times 18 = 180 \text{ km/h}\)
In simple words: Multiply m/s by \(\frac{18}{5}\) to convert to km/h.

Exam Tip: Remember conversion factor: m/s to km/h multiply by \(\frac{18}{5}\); km/h to m/s multiply by \(\frac{5}{18}\).

Question IV. (ii) Convert: 20 m/s into km/h
Answer:
\(20 \text{ m/s} = 20 \times \frac{18}{5} \text{ km/h}\)
\(= 4 \times 18 = 72 \text{ km/h}\)
In simple words: Multiply by \(\frac{18}{5}\) to get km/h.

Exam Tip: Double check multiplication steps.

Question IV. (iii) Convert: 108 km/hr into m/s
Answer:
\(108 \text{ km/hr} = 108 \times \frac{5}{18} \text{ m/s}\)
\(= 6 \times 5 = 30 \text{ m/s}\)
In simple words: Multiply km/h by \(\frac{5}{18}\) to convert to m/s.

Exam Tip: \(108 \div 18 = 6\), simplifying the calculation.

Question IV. (iv) Convert: 26 km/h into m/s
Answer:
\(26 \text{ km/h} = 26 \times \frac{5}{18} \text{ m/s}\)
\(= \frac{130}{18} = \frac{65}{9} \approx 7.22 \text{ m/s}\)
In simple words: Multiply by \(\frac{5}{18}\) and reduce the fraction.

Exam Tip: Leaving fractions in decimal form or simplest fractional form is acceptable unless specified.

Question V. A body covers a distance of 4 km in 5 mins. Calculate his speed in km/hr.
Answer:
Distance = 4 km
Time = 5 minutes = \(\frac{5}{60} \text{ hours} = \frac{1}{12} \text{ hours}\)
\(\text{Speed} = \frac{\text{Distance}}{\text{Time}} = \frac{4}{\frac{1}{12}} = 4 \times 12 = 48 \text{ km/hr}\)
In simple words: Convert minutes into hours first, then apply the speed formula.

Exam Tip: Always verify unit consistency (km with hours, meters with seconds).

Question VI. A motorist covers a distance of 3 km in 6 min. Calculate speed in (i) m/s (ii) cm/s
Answer:
Distance = 3 km = \(3000 \text{ m} = 300000 \text{ cm}\)
Time = 6 min = \(6 \times 60 = 360 \text{ s}\)
(i) Speed in m/s = \(\frac{3000}{360} = \frac{300}{36} = \frac{25}{3} \approx 8.33 \text{ m/s}\)
(ii) Speed in cm/s = \(\frac{300000}{360} = \frac{30000}{36} = \frac{2500}{3} \approx 833.33 \text{ cm/s}\)
In simple words: Convert kilometers to meters/centimeters and minutes to seconds before calculating speed.

Exam Tip: Watch out for conversion factors: \(1 \text{ km} = 1000 \text{ m}\), \(1 \text{ m} = 100 \text{ cm}\).

Question VII. Light travels with a speed of \(3 \times 10^8 \text{ m/sec}\). How long does the light take from the sun which is \(15 \times 10^{11} \text{ m}\) away?
Answer:
Speed = \(3 \times 10^8 \text{ m/s}\)
Distance = \(15 \times 10^{11} \text{ m}\)
\(\text{Time} = \frac{\text{Distance}}{\text{Speed}}\)
\(\text{Time} = \frac{15 \times 10^{11}}{3 \times 10^8} = 5 \times 10^3 \text{ seconds}\)
\(= 5000 \text{ seconds} = \frac{5000}{60} \text{ minutes} \approx 83.33 \text{ minutes}\)
In simple words: Divide the distance to the sun by the speed of light to find the time taken.

Exam Tip: Practice laws of exponents when dividing powers of 10.

Question VIII. (i) A car takes 20 minutes to cover a distance of 15 km. Calculate the speed in km/hr.
Answer:
Distance = 15 km
Time = 20 minutes = \(\frac{20}{60} \text{ hr} = \frac{1}{3} \text{ hr}\)
\(\text{Speed} = \frac{15}{\frac{1}{3}} = 15 \times 3 = 45 \text{ km/hr}\)
In simple words: Convert time into hours by dividing by 60, then calculate speed.

Exam Tip: Keeping fractions unsimplified until the final step reduces calculation errors.

Question VIII. (ii) I went from my house to the playground 300 m away in 10 minutes. I ran back and reached in two minutes. What was my average speed?
Answer:
Total distance = Distance (to playground) + Distance (back home) = \(300 \text{ m} + 300 \text{ m} = 600 \text{ m}\)
Total time = \(10 \text{ minutes} + 2 \text{ minutes} = 12 \text{ minutes} = 12 \times 60 = 720 \text{ seconds}\)
\(\text{Average Speed} = \frac{\text{Total Distance}}{\text{Total Time}}\)
\(\text{Average Speed} = \frac{600 \text{ m}}{720 \text{ s}} = \frac{60}{72} = \frac{5}{6} \approx 0.83 \text{ m/s}\)
In simple words: Average speed equals total distance divided by total time taken.

Exam Tip: Average speed is NEVER the average of two speeds; always use total distance over total time.

Question VIII. (iii) Rajdhani express takes 3 hrs to cover 315 km. Shatabdi express takes 6 hours to cover the distance of 600 km. Find the speed of both the express trains. Which express train will cover the distance of 400 km in less time?
Answer:
Speed of Rajdhani Express = \(\frac{315 \text{ km}}{3 \text{ hrs}} = 105 \text{ km/hr}\)
Speed of Shatabdi Express = \(\frac{600 \text{ km}}{6 \text{ hrs}} = 100 \text{ km/hr}\)
Time taken by Rajdhani to cover 400 km = \(\frac{400}{105} \approx 3.81 \text{ hours}\)
Time taken by Shatabdi to cover 400 km = \(\frac{400}{100} = 4 \text{ hours}\)
Therefore, Rajdhani Express will cover the distance of 400 km in less time.
In simple words: Calculate individual speeds first, then determine travel time for 400 km.

Exam Tip: The train with higher speed takes less time for the same distance.

Question VIII. (iv) The odometer of car reads 10532.0 km at start and 10850.0 km at end. If car takes 12 hour to complete its journey. Then calculate its average speed in km/hr, km/min and km/s.
Answer:
Total distance = \(10850.0 \text{ km} - 10532.0 \text{ km} = 318 \text{ km}\)
Time = 12 hours = \(12 \times 60 = 720 \text{ minutes} = 12 \times 3600 = 43200 \text{ seconds}\)
(a) Speed in km/hr = \(\frac{318}{12} = 26.5 \text{ km/hr}\)
(b) Speed in km/min = \(\frac{318}{720} = 0.4417 \text{ km/min}\)
(c) Speed in km/s = \(\frac{318}{43200} = 0.00736 \text{ km/s}\)
In simple words: Find total distance from odometer readings and divide by time in respective units.

Exam Tip: Odometer measures total distance traveled.

Question VIII. (v) If a pendulum completes 10 oscillations in one second, what will be the time period of pendulum?
Answer:
Number of oscillations = 10
Total time = 1 second
\(\text{Time Period} = \frac{\text{Total Time}}{\text{Number of Oscillations}} = \frac{1}{10} = 0.1 \text{ seconds}\)
In simple words: Time period is the time taken for one complete oscillation.

Exam Tip: Frequency is the reciprocal of time period.

Question VIII. (vi) Calculate time period of a body if it covers 40 oscillations in 20 seconds.
Answer:
Number of oscillations = 40
Total time = 20 seconds
\(\text{Time Period} = \frac{\text{Total Time}}{\text{Number of Oscillations}} = \frac{20}{40} = 0.5 \text{ seconds}\)
In simple words: Divide total time by the number of oscillations.

Question IX. Define: (i) Oscillatory motion (ii) Simple pendulum (iii) Mean position (iv) Amplitude (v) One oscillation (vi) Time period (vii) Frequency
Answer:
(i) Oscillatory motion: The to-and-fro motion of an object about its mean position.
(ii) Simple pendulum: A small metallic bob suspended from a rigid stand by a light thread.
(iii) Mean position: The resting, central position of the bob when it is not swinging.
(iv) Amplitude: The maximum displacement of the bob from its mean position on either side.
(v) One oscillation: One complete to-and-fro movement of the pendulum bob.
(vi) Time period: The time taken by the pendulum to complete one oscillation.
(vii) Frequency: The number of oscillations completed in one second.
In simple words: These terms describe the physics and mechanics of swinging pendulums.

Exam Tip: Learn these definitions word-for-word as they frequently appear in conceptual exam sections.

Question X. Calculate time period of a body if it covers 40 oscillations in 20 seconds.
Answer:
\(\text{Time Period} = \frac{\text{Total Time}}{\text{Number of Oscillations}} = \frac{20}{40} = 0.5 \text{ seconds}\)
In simple words: Time period is 0.5 seconds per oscillation.

Exam Tip: State units clearly.

Question XI. A simple pendulum take 32 seconds for completing 20 oscillations. Calculate its time period.
Answer:
Total time = 32 seconds
Number of oscillations = 20
\(\text{Time Period} = \frac{32}{20} = 1.6 \text{ seconds}\)
In simple words: Divide 32 by 20 to find the time for one oscillation.

Exam Tip: Keep decimal format clean.

Question XII. If a pendulum completes 10 oscillations in one second, what will be the time period of pendulum?
Answer:
\(\text{Time Period} = \frac{1}{10} = 0.1 \text{ seconds}\)
In simple words: One-tenth of a second per oscillation.

Exam Tip: Quick inverse relation with frequency.

Question XIII. Define graph for uniform and non- uniform motion.
Answer:
Uniform motion graph: A distance-time graph that forms a straight line, indicating constant speed.
Non-uniform motion graph: A distance-time graph that forms a curved line, indicating varying speed.
In simple words: Straight line means uniform speed; curved line means changing speed.

Exam Tip: Draw miniature thumbnail sketches in exams when defining these graphs.

Question XIV. Plot the distance time graph for an electronic toy train
Answer:
Data table:
Distance (m): 5, 10, 15, 20
Time (s): 1, 2, 3, 4

In simple words: Plot time on the x-axis and distance on the y-axis to get a straight line graph.

Exam Tip: Label axes with proper quantities and units.

Question XV. A small kid is riding a bicycle in a park. Plot the observation of distance travelled by child's cycle. (Distance: 5, 7, 10, 6; Time: 10, 20, 30, 40)
Answer:
Plot points (10, 5), (20, 7), (30, 10), (40, 6) on a distance-time graph and connect them with consecutive line segments representing non-uniform motion.
In simple words: Connect data points with a freehand curve or straight line segments to show varying speed.

Exam Tip: Irregular distance values indicate changing speed.

Question XVI. Plot a distance time graph for a body moving a uniform speed of 2 m/s.
Answer:
Data points: (1s, 2m), (2s, 4m), (3s, 6m), (4s, 8m), (5s, 10m).
The plotted points form a straight diagonal line starting from the origin, representing uniform speed.
In simple words: A constant speed of 2 m/s creates a straight line graph with a steady upward slope.

Exam Tip: Uniform speed graphs always pass through the origin if motion starts at zero time.

Question XVII. Plot the graph between distance and time using given data and answer questions: (Time 1,2,3,4,5 hrs; Distance 10,20,30,40,50 km)
Answer:
a. What is the type of motion? - Uniform motion.
b. What is the speed of paz car when Time = 9 hours and Distance = 90 km? - Speed = \(\frac{90}{9} = 10 \text{ km/hr}\).
c. Is the speed of the car constant? - Yes, because it covers equal distances in equal intervals of time.
In simple words: Constant speed means uniform motion represented by a straight line.

Exam Tip: Verify speed consistency by checking multiple rows of the table.

MODULE – 8

Question I. Fill in the blanks: (i) The direction of the path in which light is travelling is called a ____________. (ii) The stream of light formed by a number of rays is called ______________. (iii) A plane mirror ______________ all light falling on it. (iv) A plane mirror forms ______________ image. (v) Speed of light in vacuum is___________.
Answer:
(i) ray of light
(ii) beam of light
(iii) reflects
(iv) virtual and erect
(v) \(3 \times 10^8 \text{ m/s}\)
In simple words: These blanks cover fundamental properties of light, reflection, and optical speeds.

Exam Tip: Memorize the exact speed of light in vacuum.

Question II. Answer in one word: (i) The phenomenon of light travelling in a straight line. (ii) An image that can be obtained on-screen. (iii) A beam of light which comes from a broad source of light & converge at a point.
Answer:
(i) Rectilinear propagation
(ii) Real image
(iii) Convergent beam
In simple words: Straight-line travel is rectilinear propagation; screen-projected images are real.

Exam Tip: Virtual images cannot be caught on a screen.

MODULE – 9

Question I. Fill in the blanks: (i) A ______________ mirror forms enlarged image. (ii) ______________ is used as rear view mirror in cars. (iii) When we polish a spherical surface on the ______________ side we get a convex mirror. (iv) In car head lights, we use ______________ mirrors. (v) Image formed in convex mirror is always ______________, ______________ & ______________ in size.
Answer:
(i) concave
(ii) Convex mirror
(iii) inner
(iv) concave
(v) virtual, erect, diminished (smaller)
In simple words: Concave mirrors magnify; convex mirrors give a wide, diminished view.

Exam Tip: Convex mirrors always form virtual, erect, and smaller images regardless of object distance.

Question II. Answer the following questions: (i) Doctors sometimes use a mirror on their foreheads to examine internal parts. What type of mirror is it? (ii) Mention two uses of (a) Concave mirror (b) Convex mirror (c) Plane mirror (iii) Which mirror / mirrors always form virtual image?
Answer:
(i) Concave mirror.
(ii) (a) Concave mirror: Used by dentists and in solar furnaces. (b) Convex mirror: Used as rear-view mirrors in vehicles and shop security mirrors. (c) Plane mirror: Used in dressing tables and kaleidoscopes.
(iii) Plane mirror and convex mirror.
In simple words: Different mirrors have unique reflective properties suited for specific practical applications.

Exam Tip: Practice mirror uses as they frequently appear in application-based questions.

Question III. Observe the given diagram and answer the followed questions: (i) What does P, F, C represent? (ii) What type of mirror is used? (iii) What kind of image is being formed and where?
Answer:
(i) P = Pole, F = Focus, C = Centre of curvature.
(ii) Concave mirror.
(iii) Real and inverted image (when object is beyond focus).
In simple words: Parallel rays converge at the focus of a concave mirror.

Exam Tip: Learn principal axis definitions and focal length relations.

Question IV. Correct the following statements: (i) A convex mirror gives only real images. (ii) Image formed by convex mirror is of same size as that of object.
Answer:
(i) A convex mirror gives only virtual images.
(ii) Image formed by a convex mirror is always smaller (diminished) in size than that of the object.
In simple words: Convex mirrors only form virtual, diminished images.

Question I. Label the figure and answer: (i) Identify and define a, b, c, d and e. (ii) What is reflection? (iii) What are the laws of reflection?
Answer:
(i) a = Incident ray, b = Reflected ray, c = Plane mirror, d = Normal, e = Angle of incidence / reflection.
(ii) Reflection: The bouncing back of light when it strikes a polished or shiny surface.
(iii) Laws of reflection: (1) The incident ray, reflected ray, and normal all lie in the same plane. (2) Angle of incidence is equal to angle of reflection (\(\angle i = \angle r\)).
In simple words: Light bounces off mirrors following strict geometric laws.

Exam Tip: Draw clear, neat ray diagrams with arrows indicating direction.

Question II. Give reasons: (i) In medical vans used to transport patients, 'AMBULANCE' is inscribed laterally inverted. Why? (ii) We can see light through a straight tube but not through a bent tube. Why?
Answer:
(i) Due to lateral inversion in rear-view mirrors, the laterally inverted word appears straight to the driver ahead.
(ii) Light travels in a straight line (rectilinear propagation), which gets blocked in a bent tube.
In simple words: Lateral inversion helps rearview reading; rectilinear propagation stops light in bent pipes.

Question III. Draw a ray diagram to show reflection through concave mirror.
Answer:
[Provide a sketch showing parallel rays striking a concave mirror and converging at focus F.]
In simple words: Parallel incident rays converge at the focus after reflecting from a concave mirror.

Exam Tip: Always mark arrows on incoming and outgoing rays.

Question IV. Give reason: (i) Why do we prefer convex mirror as a rear-view mirror? (ii) Concave mirrors are used for shaving purpose.
Answer:
(i) Convex mirrors provide a wider field of view and always form erect, diminished images.
(ii) Concave mirrors form magnified, erect images when held close to the face, helping in a close shave.
In simple words: Convex gives wide view; concave gives magnified view.

Question I. State true or false: (i) Convex mirrors are used in spectacles. (ii) Convex lens is also called magnifying glass. (iii) Image formed by concave lens is always virtual, erect & smaller in size.
Answer:
(i) False
(ii) True
(iii) True
In simple words: Convex lenses magnify and concave lenses form smaller virtual images.

Exam Tip: Spectacles use spherical lenses, not mirrors.

Question II. Correct the following statements: (i) Mixing of colours of rainbow give black colour. (ii) White light is a composition of 10 colours. (iii) Convex lens is called diverging lens. (iv) Magnifying glass is made up of concave lenses.
Answer:
(i) Mixing of colours of rainbow gives white light.
(ii) White light is a composition of 7 colours.
(iii) Concave lens is called diverging lens (or convex lens is converging).
(iv) Magnifying glass is made up of a convex lens.
In simple words: White light splits into 7 colors; convex lenses converge and act as magnifiers.

Question III. Fill in the blanks: (i) Concave lenses are also called ______________. (ii) The band of seven colours obtained as a result of dispersion is known as _______________. (iii) During rainbow formation, ___________act like small prisms.
Answer:
(i) diverging lenses
(ii) spectrum
(iii) water droplets
In simple words: Water droplets disperse sunlight into a spectrum forming rainbows.

Exam Tip: Dispersion is the splitting of white light into its component colors.

Question IV. Answer in one word: (i) Phenomenon of breaking of white light into spectrum. (ii) A mechanical arrangement used to demonstrate composition of white light. (iii) A transparent glass piece thinner in the middle and thicker at the edges. (iv) Bouncing back of light. (v) Image obtained on screen. (vi) Absence of all colours.
Answer:
(i) Dispersion
(ii) Newton's disc
(iii) Concave lens
(iv) Reflection
(v) Real image
(vi) Black
In simple words: These single-word answers summarize core optics concepts.

Question V. Which mirror will be used for following purpose? (i) Virtual and larger image (ii) Real image (iii) Virtual image of same size (iv) Virtual image of smaller size
Answer:
(i) Concave mirror
(ii) Concave mirror
(iii) Plane mirror
(iv) Convex mirror
In simple words: Different mirrors create specific image sizes and natures based on positioning.

Exam Tip: Memorize mirror characteristics table to answer quickly.

CHEMISTRY - MODULE – 01/02/03 (ACIDS, BASES AND SALTS)

Question Q.1. Name the following: (i) Substances which furnish hydronium ion in solution. (ii) Substances which turn blue litmus solution red. (iii) Substances which furnish hydroxyl ion in solution. (iv) Substances which turn turmeric paper red. (v) Chemical name for salt consumed everyday. (vi) Base used in fire extinguisher. (vii) Commonly used antacid. (viii) Substances on which litmus has no effect. (ix) Colour of turmeric solution in soap. (x) Examples of two mineral and organic acids. (xi) Name and colour of two laboratory salts.
Answer:
(i) Acids
(ii) Acids
(iii) Bases
(iv) Bases
(v) Sodium chloride
(vi) Sodium bicarbonate
(vii) Milk of magnesia (Magnesium hydroxide)
(viii) Neutral substances
(ix) Reddish-brown
(x) Mineral acids: Hydrochloric acid, Sulphuric acid; Organic acids: Acetic acid, Citric acid
(xi) Copper sulphate (Blue), Iron sulphate (Green)
In simple words: Chemical indicators and classifications help identify acidic and basic substances.

Exam Tip: Keep examples of mineral and organic acids handy for distinction.

Question Q.2. Solve the crossword given below (Across & Down clues)
Answer:
Across: 2. Soap (Sodium hydroxide), 4. Turmeric, 5. Antacid, 6. Litmus, 9. Alkali, 10. China rose, 12. Formic acid.
Down: 1. Neutralisation, 3. Indicator, 7. Base, 8. Acid, 11. Salt.
In simple words: Crossword terms test key chemical vocabulary.

Question Q.3. Match the following:
Answer:
(i) Sodium chloride - (e) Salt
(ii) Water - (a) Neutral media
(iii) Lime juice - (f) Acid
(iv) Lime water - (h) Base
(v) Methyl orange - (g) Indicator
(vi) Litmus - (c) Lichen
(vii) Sting of bees - (b) Formic acid
(viii) To remove acidity - (d) Magnesium hydroxide
In simple words: Matching links substances with their correct chemical properties or sources.

Exam Tip: Match known items first to eliminate confusion.

Question Q.4. Fill in the blanks: (i) New substance formed when acid reacts with base (ii) Heat is ________ during neutralization (iii) Sulphuric acid + lime water reaction mixture becomes ________ (iv) ________ acid is present in stomach (v) Milk of magnesia base (vi) Calamine lotion contains ________
Answer:
(i) Salt and water
(ii) evolved (released)
(iii) neutral
(iv) Hydrochloric
(v) Magnesium hydroxide
(vi) Zinc carbonate
In simple words: Neutralization produces salt, water, and heat while balancing pH.

Exam Tip: General equation: Acid + Base \(\rightarrow\) Salt + Water + Heat.

Question Q.5. Name the acids present in: (i) Curd (ii) Spinach (iii) Tamarind (iv) Amla (v) Aerated drinks (vi) Vinegar
Answer:
(i) Lactic acid
(ii) Oxalic acid
(iii) Tartaric acid
(iv) Ascorbic acid (Vitamin C)
(v) Carbonic acid
(vi) Acetic acid
In simple words: Natural food items contain specific organic acids.

Question Q.6. Name the bases present in: (i) Lime water (ii) Soap (iii) Milk of magnesia (iv) Slaked lime (v) Caustic soda (vi) Caustic potash
Answer:
(i) Calcium hydroxide
(ii) Sodium hydroxide / Potassium hydroxide
(iii) Magnesium hydroxide
(iv) Calcium hydroxide
(v) Sodium hydroxide
(vi) Potassium hydroxide
In simple words: Common cleaning agents and antacids contain strong and weak metallic hydroxides.

Question Q.7. Give natural source of: (i) Citric acid (ii) Lactic acid (iii) Acetic acid (iv) Tartaric acid (v) Oxalic acid (vi) Maleic acid
Answer:
(i) Citrus fruits (lemon, orange)
(ii) Curd
(iii) Vinegar
(iv) Tamarind, grapes
(v) Spinach, tomato
(vi) Apples
In simple words: Organic acids are naturally extracted from plants and animal products.

Question Q.8. What are colour changes of indicators in acidic, basic, neutral media? (China rose, Red litmus, Methyl orange, Phenolphthalein, Turmeric powder, Blue litmus)
Answer:
- China rose: Acidic = Dark pink/magenta, Basic = Green, Neutral = No change
- Red litmus: Acidic = No change, Basic = Turns blue, Neutral = No change
- Methyl orange: Acidic = Red, Basic = Yellow, Neutral = Orange
- Phenolphthalein: Acidic = Colourless, Basic = Pink, Neutral = Colourless
- Turmeric powder: Acidic = Yellow, Basic = Reddish-brown, Neutral = Yellow
- Blue litmus: Acidic = Turns red, Basic = No change, Neutral = No change
In simple words: Indicators show distinct color shifts across different pH environments.

Exam Tip: Make a summary table of indicator color changes for quick revision.

Question Q.9. Choose correct alternatives for methyl orange, acidic soil, litmus test, phenolphthalein, and orange juice.
Answer:
(i) (c) red
(ii) (a) quicklime
(iii) (b) basic in nature
(iv) (a) it turns pink
(v) (b) citric acid
In simple words: Multiple-choice questions testing indicator behavior and acid-base neutralization.

Exam Tip: Phenolphthalein turns pink in basic solutions and remains colorless in acidic solutions.

QUESTION BANK - ACID AND BASES

Question Q.1. Answer questions on litmus sources, acid uses, indigestion causes, ant stings, soil treatment, base uses, and neutralization examples.
Answer:
(i) Litmus is extracted from lichens.
(ii) Acids are used in food preservation and manufacturing fertilizers.
(iii) Excess stomach acid causes indigestion; treated with antacids like milk of magnesia.
(iv) Ant stings inject formic acid; neutralized using moist baking soda or calamine lotion.
(v) Excessive use of chemical fertilizers makes soil acidic; treated with quicklime or slaked lime.
(vi) Bases are used in making soaps and antacids.
(vii) Distilled water is neutral; verified using blue and red litmus paper (no color change).
(viii) Neutralization is the reaction between an acid and a base producing salt and water (e.g., HCl + NaOH \(\rightarrow\) NaCl + H\(_2\)O).
(ix) Dorji can use an indicator like turmeric or china rose to identify acidic, basic, and neutral soft drinks.
(x) Turmeric turns reddish-brown in sodium hydroxide (basic), remains yellow in hydrochloric acid (acidic) and sugar solution (neutral).
(xi) The solution is basic in nature because blue litmus paper remains unaffected in basic and neutral solutions, but here the context confirms basicity.
In simple words: Practical chemistry applications involve neutralization, indicators, and everyday remedies.

Exam Tip: Practice writing balanced neutralization chemical reactions.

Question Q.2. Define with examples: Indicators, Acid rain, Natural indicators, Neutralization reaction, Antacids, Neutral substances, Synthetic indicators.
Answer:
(i) Indicators: Dyes that change color in acidic or basic media (e.g., litmus).
(ii) Acid rain: Rain containing high levels of acidic pollutants like sulfur dioxide and nitrogen dioxide.
(iii) Natural indicators: Indicators obtained from natural sources (e.g., turmeric, china rose).
(iv) Neutralization reaction: Reaction between acid and base forming salt and water.
(v) Antacids: Mild bases used to neutralize stomach acidity (e.g., milk of magnesia).
(vi) Neutral substances: Substances that are neither acidic nor basic (e.g., pure water, sodium chloride solution).
(vii) Synthetic indicators: Man-made chemical indicators (e.g., phenolphthalein, methyl orange).
In simple words: Definitions cover key chemical classifications and terms.

Exam Tip: Always provide examples when defining scientific terms.

Question Q.3. Differentiate between: (i) Acids and bases (ii) Base and alkali (iii) Mineral and organic acids (iv) Concentrated and dilute acids
Answer:
(i) Acids: Sour in taste, turn blue litmus red. Bases: Bitter in taste, soapy to touch, turn red litmus blue.
(ii) Base: Any metal oxide or hydroxide. Alkali: A water-soluble base.
(iii) Mineral acids: Derived from minerals (e.g., HCl). Organic acids: Derived from plants and animals (e.g., acetic acid).
(iv) Concentrated acids: High amount of acid with little water. Dilute acids: Large amount of water with small amount of acid.
In simple words: Differences highlight chemical properties, solubility, sources, and concentration.

Exam Tip: Tabular differences score better in board evaluations.

Question Q.4. Give reasons for vinegar sourness, avoiding direct tasting, organic matter addition, copper cleaning, ammonia fertilizers, soap-turmeric/vegetable stain reactions, and factory waste treatment.
Answer:
(i) Vinegar contains acetic acid.
(ii) Chemicals can be corrosive or harmful to health.
(iii) Organic matter neutralizes excess soil acidity.
(iv) Lemon is acidic and dissolves basic copper oxide/carbonate stains on copper vessels.
(v) Ammonia is basic and neutralizes acidic soil.
(vi) Baking soda is basic; china rose reacts primarily with solutions.
(vii) Turmeric/vegetable stains are basic in soap, turning reddish-brown.
(viii) Antacid tablets neutralize excess stomach acid.
(ix) Calamine contains zinc carbonate which neutralizes formic acid from ant stings.
(x) Factory wastes are acidic; neutralizing them prevents aquatic life harm.
In simple words: Scientific reasoning explains everyday chemical phenomena.

Exam Tip: Link every reasoning question back to acid-base neutralization or indicator color changes.

Question Q.5. Substance 'X' is obtained by reaction of sulphuric acid and sodium hydroxide. Identify 'X' and write its chemical formula.
Answer:
Substance 'X' is Sodium sulphate.
Chemical formula: \(\text{Na}_2\text{SO}_4\)
In simple words: Neutralizing sodium hydroxide with sulphuric acid forms sodium sulphate salt and water.

Exam Tip: Balance valence numbers when writing salt formulas.

Question Q.6. Take water in a test tube, add blue litmus, blow air. It turns red. Explain.
Answer:
Exhaled air contains carbon dioxide, which dissolves in water to form carbonic acid (a weak acid), turning blue litmus red.
In simple words: Carbon dioxide in breath forms a mild acid in water.

Exam Tip: Non-metal oxides are acidic in nature.

Question Q.7. Complete neutralization reactions: (i) Potassium hydroxide + Sulphuric acid (ii) Calcium hydroxide + Hydrochloric acid (iii) Carbonic acid + Sodium hydroxide
Answer:
(i) Potassium sulphate + Water (\(\text{K}_2\text{SO}_4 + 2\text{H}_2\text{O}\))
(ii) Calcium chloride + Water (\`CaCl\)_2 + 2H\(_2\)O)
(iii) Sodium carbonate + Water + Heat (\(\text{Na}_2\text{CO}_3 + 2\text{H}_2\text{O} + \text{Heat}\))
In simple words: Acids and bases combine to form respective salts and water.

Exam Tip: Always balance chemical equations when completing reactions.

FIBRE TO FABRIC - ASSIGNMENT & QUESTION BANK

Question Q.1. Name the following: Animal fibres, wool-yielding animals, fleece types, sorter's disease microbe, brown fleece breed, patanwadi wool quality, lohi/nali/marwari states, silk-leading country.
Answer:
(i) Wool, Silk
(ii) Sheep, goat, yak, camel
(iii) Coarse beard hair and fine soft under-hair
(iv) Bacillus anthracis
(v) Marwari sheep
(vi) Good quality hosiery wool
(vii) (a) Lohi: Punjab/Rajasthan, (b) Nali: Rajasthan/Haryana, (c) Marwari: Rajasthan
(viii) China
In simple words: Animal fiber production involves specific livestock breeds and global producers.

Exam Tip: Learn Indian sheep breeds and their regional states.

Question Q.2. Select odd one out with reason: (i) Cotton, silk, wool (ii) Camel, sheep, silk worm (iii) Shearing, scouring, reeling (iv) Sorting, cocoon, boiling, carding (v) Angora, merino, tassar
Answer:
(i) Cotton - plant fibre; others are animal fibres.
(ii) Silk worm - insect; others are mammals.
(iii) Reeling - silk process; others are wool processes.
(iv) Cocoon - biological structure; others are wool processing steps.
(v) Tassar - type of silk; others are wool-yielding sheep/goat breeds.
In simple words: Identify the item belonging to a different category and state why.

Question Q.3. Fill in the blanks: Angora wool source, camel types, sheep feed, sorter's disease, wool production leader, cocoon color, silk worm feed.
Answer:
(i) Angora goat
(ii) Dromedary, Bactrian (or camel, Llama/Alpaca)
(iii) Grass, leaves, pulses/corn
(iv) Anthrax (sorter's disease)
(v) Australia
(vi) White or yellowish-white
(vii) Mulberry leaves
In simple words: Silkworms feed on mulberry leaves, producing cocoons yielding natural silk.

Exam Tip: Mulberry silk is the most common commercial variety.

Question Q.4. Choose the right answer for non-fibers, non-animal fibers, synthetic fibers, fiber composition, and carpet wool sheep.
Answer:
(i) (d) leather
(ii) (c) jute
(iii) (b) rayon
(iv) (b) proteins
(v) (a) Marwari sheep
In simple words: Natural animal fibers are protein-based; rayon is synthetic.

Exam Tip: Wool and silk are protein fibers, while plant fibers like cotton and jute are cellulose-based.

Question Q.5. (Shearing machine figure) Define shearing, why done in summers, is it painful?
Answer:
(i) Shearing: The process of removing the fleece of a sheep along with a thin layer of dead skin.
(ii) Done in summer so sheep do not feel hot and can survive without their thick fur coat.
(iii) No, it is not painful because the uppermost layer of skin is dead tissue.
In simple words: Shearing acts like a haircut for sheep, done safely in warm weather.

Exam Tip: Emphasize that dead skin cells prevent pain during shearing.

Question Q.6. Solve crossword for Down and Across clues (Fiber to fabric).
Answer:
Down: 1. Sericulture, 4. Pashmina, 7. Bombyx mori, 8. Silk, 11. Sheep.
Across: 2. Angora, 3. Cocoon, 5. Carding, 6. Marwari, 8. Anthrax, 9. Alpaca, 10. Mulberry.
In simple words: Crossword covers sericulture terminology and wool breeds.

Exam Tip: Scientific name of silkmoth is Bombyx mori.

Question Q.7. Complete the matrix for wool processing steps (Shearing, Scouring, Sorting, Spinning/Carding).
Answer:
Step 2: Scouring (washing sheared skin in tanks to remove grease, dirt, and dust).
Step 3: Sorting / Carding (separating hair of different textures and passing through metal teeth).
In simple words: Wool processing flows from shearing and scouring to sorting, dyeing, and spinning.

Exam Tip: Memorize the sequence: Shearing \(\rightarrow\) Scouring \(\rightarrow\) Sorting \(\rightarrow\) Cleaning \(\rightarrow\) Dyeing \(\rightarrow\) Spinning.

WATER - A PRECIOUS RESOURCE

Question Q.1. Fill in the blanks: Water states, liquid water locations, transpiration, infiltration, water scarcity, ultimate source, contamination, water-borne diseases, rainwater harvesting, saline water, natural resource, river pollution, agriculture use, scarcity reasons.
Answer:
(i) Ice, snow
(ii) Oceans, rivers, underground
(iii) transpiration
(iv) infiltration
(v) increasing
(vi) Rain
(vii) Sewage/industrial waste
(viii) Cholera, typhoid
(ix) Rainwater harvesting
(x) saline
(xi) water
(xii) sewage/garbage
(xiii) agricultural
(xiv) population growth / deforestation
In simple words: Water exists in three states and is vital for life, though scarce in usable forms.

Exam Tip: Over 97% of Earth's water is in oceans and is saline.

Question Q.2. The diagram shows states of water are interchangeable. Prove this statement correct.
Answer: Ice melts into water (melting), water boils into steam (vaporization), steam condenses into water (condensation), and water freezes into ice (freezing), proving interconvertibility.
In simple words: Water changes between solid, liquid, and gas states through heating and cooling.

Exam Tip: Mention phase changes clearly (melting, boiling, freezing, condensation).

Question Q.3. Match the following water terms.
Answer:
(i) Water fit for consumption - (d) Potable water
(ii) Water found in wells - (e) Underground water
(iii) Liquid present in human beings - (f) Water
(iv) Gas extremely soluble in water - (c) CO2 (carbon dioxide)
(v) Pure water used for medicinal purpose - (b) Distilled water
(vi) Water containing harmful substances - (a) Polluted water
In simple words: Matching links water categories with definitions.

Exam Tip: Potable water means water safe for drinking.

Question Q.4. Select odd one out giving reasons: (i) Ocean, ground water, lakes (ii) Water, ice, snow (iii) Infiltration, aquifer, drip irrigation (iv) Water harvesting, bawris, aquifer
Answer:
(i) Ground water - underground source; others are surface water sources.
(ii) Water - liquid state; others are solid states of water.
(iii) Drip irrigation - water conservation method; others are underground water terms.
(iv) Aquifer - underground water reservoir; others are ancient/modern water-saving/collection structures.
In simple words: Categorize based on state, location, or function.

Exam Tip: Provide solid scientific reasoning for odd-one-out questions.

Question Q.5. Name the following: Water circulation, seeping process, underground water level, available usable water percentage, World Water Day date, ground water source.
Answer:
(i) Water cycle
(ii) Infiltration / Seepage
(iii) Water table
(iv) Less than 1%
(v) March 22
(vi) Rainwater / surface water infiltration
In simple words: These terms cover hydrological cycle and water table statistics.

Exam Tip: Remember World Water Day is March 22.

Question Q.6. Tick correct answer: (i) Seeping of water (ii) Excessive rains cause (iii) Freshwater present is (iv) Saline water found in
Answer:
(i) infiltration
(ii) floods
(iii) less
(iv) oceans
In simple words: Infiltration recharges groundwater; oceans hold saline water.

Exam Tip: Distinguish carefully between floods and drought.

Question Q.7. Write true or false: Water scarcity, saline water definition, Earth surface water cover, groundwater vs river water volume.
Answer:
(i) True
(ii) False
(iii) True
(iv) True
In simple words: Groundwater stores more freshwater than surface rivers and lakes.

Question Q.1. Classify changes as physical or chemical: Sugar burning, butter melting, milk souring, wet hair drying, lime mixing with water, coal burning, plant growth, food spoiling, crackers bursting, cutting vegetables.
Answer:
(i) Burning of sugar - Chemical change
(ii) Melting of butter - Physical change
(iii) Souring of milk - Chemical change
(iv) Drying of wet hair - Physical change
(v) Mixing lime with water - Chemical change
(vi) Burning of coal - Chemical change
(vii) Growth of plants to trees - Chemical change
(viii) Spoiling of food - Chemical change
(ix) Bursting of crackers - Chemical change
(x) Cutting of vegetables - Physical change
In simple words: Physical changes alter shape/state; chemical changes form new substances.

Exam Tip: Irreversibility and formation of new substances point to chemical changes.

Question Q.2. Name the following: Copper sulphate common name, gas evolved in vinegar-baking soda reaction, 3 daily life alloys, 2 rusting factors, color-changing chemical change example.
Answer:
(i) Blue vitriol
(ii) Carbon dioxide (\(\text{CO}_2\))
(iii) Brass, bronze, stainless steel
(iv) Oxygen and moisture (water)
(v) Rusting of iron (grey to reddish-brown) or reaction of iron with copper sulphate solution (blue to green)
In simple words: Common chemical substances have specific trade names and color indicators.

Exam Tip: Brass is an alloy of copper and zinc; bronze is copper and tin.

Question Q.3. Metal X burns with dazzling white flame to form Y. Y reacts with water to form Z which turns red litmus blue. Identify X, Y, Z and write reactions.
Answer:
X = Magnesium (Mg)
Y = Magnesium oxide (MgO)
Z = Magnesium hydroxide (\(\text{Mg(OH)}_2\))
Reactions:
\(2\text{Mg} + \text{O}_2 \rightarrow 2\text{MgO}\)
\(\text{MgO} + \text{H}_2\text{O} \rightarrow \text{Mg(OH)}_2\)
In simple words: Magnesium burns bright white, forming basic magnesium oxide when dissolved in water.

Question Q.4. (Renumbered as Q.7 in source) Metal A changes color of copper sulphate solution when added. Name A, write reaction, and change type.
Answer:
(i) Metal A: Iron (Fe)
(ii) Reaction: \(\text{Fe} + \text{CuSO}_4 \rightarrow \text{FeSO}_4 + \text{Cu}\)
(iii) Type of change: Chemical change (displacement reaction)
In simple words: More reactive iron displaces copper from copper sulphate, turning blue solution green.

Exam Tip: Displacement reactions are classic examples of chemical changes.

Question Q.5. Solve crossword for Across and Down clues (Physical & Chemical Changes).
Answer:
Across: 1. Acid, 6. Alloy, 7. Evaporation, 8. Irreversible.
Down: 2. Crystal, 3. Physical (or chemical if broken), 4. Brown, 5. Vinegar.
In simple words: Crossword terms test chemical reactions, alloys, and crystallization.

Exam Tip: Learn definitions of alloys and crystallization.

Question Q.6. Match columns A, B, and C for physical changes, copper sulphate, iron, carbon, spoilage of food, magnesium.
Answer:
(i) Physical changes - (iv) Generally reversible - (iii) no new substance is formed
(ii) copper sulphate - (v) reacts with zinc - (v) Zinc sulphate is formed
(iii) iron - (i) reacts with sulphur - (i) Rust (or chemical change)
(iv) carbon - (ii) irreversible - (ii) Chemical change
(v) spoilage of food - (ii) irreversible - (ii) Chemical change
(vi) magnesium - (vi) oxygen and water - (vi) Endothermic reaction
In simple words: Multi-column matching tests properties of metals, non-metals, and reactions.

Question Q.7. Complete reactions: (i) CaO + CO2 (ii) Carbon + oxygen (iii) Magnesium oxide + water (iv) Magnesium + oxygen
Answer:
(i) \(\text{CaO} + \text{CO}_2 \rightarrow \text{CaCO}_3\) (Calcium carbonate)
(ii) Carbon + oxygen \(\rightarrow\) Carbon dioxide (\(\text{CO}_2\))
(iii) Magnesium oxide + Water \(\rightarrow\) Magnesium hydroxide (\(\text{Mg(OH)}_2\))
(iv) Magnesium + Oxygen \(\rightarrow\) Magnesium oxide (2MgO)
In simple words: Reactants combine to form specific oxides and salts.

Exam Tip: Practice balancing word equations into chemical formulas.

Question Q.8. Fill in the blanks: Sugar dissolving, galvanization, crystallization, rust formula.
Answer:
(i) physical
(ii) galvanization
(iii) crystallization
(iv) hydrated iron (III) oxide (\(\text{Fe}_2\text{O}_3 \cdot x\text{H}_2\text{O}\))
In simple words: Dissolving sugar is physical; depositing zinc is galvanization.

Question Q.9. Tick correct answer for crystallization, biogas change, rust prevention, and physical irreversible change.
Answer:
(i) (a) pure solids only
(ii) (c) Both (a) and (b)
(iii) (d) all of these
(iv) (c) crushing of glass
In simple words: Crystallization yields pure solids; crushing glass is a physical change that cannot be reversed.

Question Q.1. (Potter figure) (i) Name the type of soil (ii) Size of particles (iii) Uses
Answer:
(i) Clayey soil
(ii) Fine particles (very small size)
(iii) Used for making pots, toys, and statues.
In simple words: Clayey soil holds water well and is moldable, making it ideal for pottery.

Question Q.2. Fill in the blanks: Percolation rate highest/least, pottery soil, deforestation name, B-horizon color, soil pores.
Answer:
(i) sandy, clayey
(ii) Clayey
(iii) Deforestation
(iv) humus
(v) pores / spaces
In simple words: Sandy soil lets water drain fastest; clayey soil retains it longest.

Question Q.3. Name the following: Humus definition, largest particle soil, darkest layer, soil organism, wind erosion, water-logged soil, most fertile soil, soil pollutants, layer beneath C-horizon, pottery soil, mountain soil states.
Answer:
(i) Humus
(ii) Sandy soil
(iii) A-horizon
(iv) Earthworm
(v) Soil erosion
(vi) Clayey soil
(vii) Loamy soil
(viii) Plastics, polythene, chemicals
(ix) Bedrock
(x) Clayey soil
(xi) Jammu & Kashmir, Himachal Pradesh
In simple words: These terms cover soil horizons, soil types, and ecological roles.

Question Q.4. Which type of soil is required for growing: (i) Wheat and gram (ii) Paddy (iii) Lentils and other pulses (iv) Cotton
Answer:
(i) Loamy / clayey-loam soil
(ii) Clayey soil (needs water retention)
(iii) Loamy soil
(iv) Black soil
In simple words: Different crops thrive best in specific soil textures.

Question Q.5. Choose the most appropriate answer: Humus and rock particles form, cotton soil, highest humus soil, smallest particle size.
Answer:
(i) (a) A-Horizon
(ii) (b) Black soil
(iii) (b) Mountain soil
(iv) (c) Clay
In simple words: Topsoil contains humus; clay has the finest particles.

Question Q.4 (Question Bank). A soil sample takes 45 minutes to percolate 900ml of water. Calculate rate of percolation.
Answer:
Volume of water = 900 mL
Time = 45 minutes
\(\text{Rate of percolation} = \frac{\text{Volume}}{\text{Time}} = \frac{900 \text{ mL}}{45 \text{ min}} = 20 \text{ mL/min}\)
In simple words: Divide water volume by percolation time.

Exam Tip: Always include mL/min as the unit for percolation rate.

Question Q.10 (Question Bank). Razia observed 200 ml water took 40 min to percolate. Calculate rate of percolation.
Answer:
\(\text{Rate of percolation} = \frac{200 \text{ mL}}{40 \text{ min}} = 5 \text{ mL/min}\)
In simple words: 200 divided by 40 gives 5 mL per minute.

Question Q.12 (Question Bank). Calculate percentage of water absorbed by soil sample of 50 gm when initial water was 50 ml and final volume was 25 ml.
Answer:
Initial volume of water (\(U_1\)) = 50 mL
Final volume of water in measuring cylinder (\(U_2\)) = 25 mL
Volume of water absorbed = \(U_1 - U_2 = 50 - 25 = 25 \text{ mL}\)
Mass of soil sample = 50 g
Percentage of water absorbed = \(\frac{\text{Volume of water absorbed}}{\text{Mass of soil}} \times 100\)
\(= \frac{25}{50} \times 100 = 50\%\)
In simple words: Subtract remaining water from initial water, then calculate percentage against soil mass.

Exam Tip: 1 mL of water has a mass of 1 g, allowing direct volume-to-mass percentage calculations.

WASTE WATER STORY - ASSIGNMENT & QUESTION BANK

Question Q.1. Fill in the blanks: Solid impurities use, transport system, last stage of sewage treatment, sewage composition.
Answer:
(i) manure / biogas generation
(ii) sewerage
(iii) chlorination / disinfection
(iv) wastewater, human excreta, food waste, oil
In simple words: Sewage treatment removes solid sludge and disinfects wastewater before release.

Exam Tip: Sewerage refers to the network of pipes transporting sewage.

Question Q.2. Answer in one word: Domestic wastewater, industrial waste, rural sewerage system, composting pit organisms.
Answer:
(i) Sewage
(ii) Industrial effluent
(iii) Septic tank / low-cost sanitation
(iv) Earthworms (Vermicomposting)
In simple words: Single-word answers categorize waste types and treatment agents.

Question Q.3. Name organic impurities, sludge gas, untreated sewage diseases, wastewater contaminants.
Answer:
(i) Feces, urine, vegetable waste, animal waste
(ii) Methane (\(\text{CH}_4\))
(iii) Cholera, typhoid, dysentery, jaundice
(iv) Pathogens, suspended solids, nutrients, heavy metals
In simple words: Sewage carries harmful organic and inorganic contaminants causing water-borne diseases.

Exam Tip: Mention water-borne diseases like cholera and jaundice when discussing untreated sewage hazards.

Question Q.4 & Q.5 & Q.6. True/False, disease not caused by sewage, wastewater definition, floating materials in wastewater treatment.
Answer:
Q.4: False (contamination can occur due to leakage or pipe damage)
Q.5: (ii) Heart attack
Q.6: (i) (a) sewage, (ii) (a) scum
In simple words: Heart attacks are non-infectious; floating grease and oil form scum in clarifiers.

Question Q1. Give one word answer: Food factories of plants, green pigment, ultimate source of energy, essential food component, autotrophs, heterotrophs.
Answer:
(i) Leaves
(ii) Chlorophyll
(iii) Sun
(iv) Nutrients
(v) Producers
(vi) Consumers
In simple words: Leaves make food via photosynthesis using sunlight and chlorophyll.

Exam Tip: Sun is the ultimate source of energy for all living organisms.

Question Q2. Fill in the blanks: Algae autotroph/heterotroph, starch test color, protein elements, photosynthesis raw materials, colored leaves photosynthesis, nitrogen-fixing bacteria, cell components, stem photosynthesis plant.
Answer:
(i) autotrophs
(ii) blue-black
(iii) nitrogen, hydrogen, oxygen
(iv) carbon dioxide, water, chlorophyll
(v) can
(vi) Rhizobium, fertilizers, manure
(vii) cell membrane, cytoplasm, nucleus
(viii) Cactus
In simple words: Plants synthesize carbohydrates through photosynthesis and absorb nitrogen with bacterial help.

Question Q3. Complete equation: Carbondioxide + Water \(\xrightarrow{\text{sunlight, chlorophyll}}\) Carbohydrate + Oxygen
Answer:
Missing terms: Water, Oxygen
In simple words: Carbon dioxide and water produce carbohydrates and oxygen in sunlight.

Question Q4. Complete table for photosynthesis raw materials (Carbon dioxide, water, sunlight, chlorophyll).
Answer:
- Carbon dioxide source: Atmosphere, enters via stomata.
- Water source: Soil, absorbed by roots.
- Sunlight source: Sun, captured by chlorophyll pigment present in leaves.
- Chlorophyll source: Cells containing chloroplasts / green parts.
In simple words: Summarizes inputs, sources, and plant parts involved in photosynthesis.

Question Q5. (Photosynthesis diagram) (i) Process name (ii) Arrow 1 absorption (iii) CO2 absorption arrow (iv) Oxygen release arrow (v) Arrow 4 energy.
Answer:
(i) Photosynthesis
(ii) Water & minerals
(iii) Arrow pointing into leaves (Carbon dioxide)
(iv) Arrow pointing out (Oxygen)
(v) Solar / Light energy
In simple words: Diagram illustrates how plants take in water, CO\(_2\), and sunlight to release oxygen.

Question Q6. Fill in the blanks: Parasitic/saprotrophic definitions, symbiotic relationship, fungus conditions, fertilizer nutrients, lichen partners, nitrogen fixer, fungal enzymes.
Answer:
(i) heterotrophs / parasites
(ii) saprotrophs
(iii) symbiotic
(iv) warm, humid
(v) Nitrogen, Phosphorus, Potassium (NPK)
(vi) alga, fungus
(vii) Rhizobium
(viii) digestive juices
(ix) solution
(x) leguminous
In simple words: Nutritional modes in plants include autotrophic, parasitic, insectivorous, and symbiotic associations.

Question Q7. Give example of: (i) Saprotroph (ii) Leguminous plant (iii) Partial heterotroph (iv) Insectivorous plant (v) Parasitic plant
Answer:
(i) Mushroom / Fungi
(ii) Pea / Gram / Bean
(iii) Mistletoe / Pitcher plant
(iv) Pitcher plant / Venus flytrap
(v) Cuscuta (Amarbel)
In simple words: Examples represent diverse plant nutrition adaptations.

Question Q8 & Q9 & Q10. Pitcher plant sequence, matching, and table completion for lichens and Rhizobium.
Answer:
Q8: (i) Sequence: d, c, a, b (Land \(\rightarrow\) Entangle \(\rightarrow\) Close \(\rightarrow\) Digest)
(ii) (a) Leaf lamina (b) Leaf apex / lid
(iii) True
(iv) Nitrogen
(v) Downward
(vi) Pitcher
(vii) (b) Providing nutrients to plants
Q9: Matching: (i)-f, (ii)-e, (iii)-b, (iv)-c, (v)-a, (vi)-d
Q10: Lichens partners: Alga & Fungus (Alga provides food, Fungus provides shelter, water & minerals). Rhizobium-Legume: Rhizobium & Leguminous plant roots (Rhizobium fixes nitrogen, legume provides shelter & food).
In simple words: Insectivorous plants trap insects to supplement nitrogen; symbiotic partners share mutual benefits.

Question Q1. Arrange in sequential order: (a) Alimentary canal parts (b) Steps of nutrition
Answer:
(a) Alimentary canal: Buccal cavity \(\rightarrow\) Oesophagus \(\rightarrow\) Stomach \(\rightarrow\) Small intestine \(\rightarrow\) Large intestine \(\rightarrow\) Rectum \(\rightarrow\) Anus.
(b) Steps of nutrition: Ingestion \(\rightarrow\) Digestion \(\rightarrow\) Absorption \(\rightarrow\) Assimilation \(\rightarrow\) Egestion.
In simple words: Food travels sequentially through the alimentary canal undergoing five stages of nutrition.

Question Q2 & Q4. Complete tables for teeth types (Milk teeth vs Permanent teeth, Incisors, Canines, Premolars, Molars counts and functions).
Answer:
- 4-year-old child: Milk teeth, 20 teeth, falling age 6-8 years.
- 25-year-old adult: Permanent teeth, 32 teeth.
- Incisors: 4 + 4 = 8, Cutting & biting.
- Canines: 2 + 2 = 4, Piercing & tearing.
- Premolars: 4 + 4 = 8, Grinding & crushing.
- Molars: 6 + 6 = 12, Chewing & grinding.
In simple words: Humans have four types of teeth performing specific chewing functions across milk and permanent sets.

Question Q3. Fill in the blanks: Ingestion definition, saliva action, tooth decay cause, alimentary canal length, digestive system constituents, digestion definition, digestive glands, stomach inner lining, tongue function, tooth socket.
Answer:
(a) ingestion
(b) sugar into simpler sugars (starch into maltose)
(c) acid, tooth decay
(d) buccal cavity, anus
(e) Alimentary canal, digestive glands
(f) digestion
(g) Salivary glands, liver, pancreas
(h) stomach, small intestine
(i) tongue
(j) jaw bone (socket)
In simple words: Digestion breaks down complex food using enzymes secreted by glands along the alimentary canal.

Question Q5. Choose correct option: Stomach lining protection, bile juice digestion role, complete digestion site.
Answer:
(i) (b) Mucous
(ii) (d) Fats
(iii) (c) Small Intestine
In simple words: Mucous protects the stomach lining; bile emulsifies fats; small intestine completes digestion.

Question Q6. Solve crossword puzzle for digestive system (Liver, tongue, anus, gall bladder, villi, pseudopodia, feces, molars, bile, saliva, ruminant, cud, etc.).
Answer:
Across: 1. Liver, 4. Tongue, 5. Anus, 7. Gall bladder, 10. Villi, 13. Sweet/sour, 14. Acid.
Down: 2. Amoeba, 3. Feces, 6. Six, 8. Liver, 9. Saliva, 11. Cow/Sheep, 12. Cud.
In simple words: Crossword terms test human and amoebic digestive anatomy.

Question Q7. Complete table for stomach secretions and functions (Mucus, Hydrochloric acid, Digestive juice).
Answer:
- Mucus: Protects the lining of stomach from HCl.
- Hydrochloric acid: (i) Kills bacteria entering with food. (ii) Creates acidic medium which helps digestive juices to act.
- Digestive juice: Breaks down proteins into simpler substances.
In simple words: Gastric juices contain acid for sterilization and enzymes for protein digestion, protected by mucus.

Question Q8 & Q9 & Q10. Label digestive system diagram, fill in blanks for digestion products (carbohydrates, proteins, fats), ruminant digestion steps, and amoeba nutrition.
Answer:
Q9: (i) Intestinal juice
(ii) (a) Glucose / sugars, (b) Amino acids, (c) Fatty acids & glycerol
(iii) Water, mineral salts
(iv) Ruminants
(v) can't, don't have
Q10: Ruminants: (a) Rumen, (b) Cud, (c) Mouth, chewing = rumination, (d) cellulose, bacteria, caecum.
Amoeba: (a) Pseudopodia, (b) Food vacuole, (c) diffused, (d) growth, maintenance, multiplication, (e) pseudopodia / cell membrane.
In simple words: Complex nutrients break down into simple forms; ruminants digest cellulose using specialized rumen bacteria.

Question Q1. Fill in the blanks: Rainfall instrument/unit, weather elements, primary energy source, climate definition, meteorologists, min/max temperature timing, recording instruments, weather vs climate.
Answer:
(i) rain gauge, mm (millimetres)
(ii) temperature, humidity, rainfall, wind speed
(iii) Sun
(iv) Climate
(v) Meteorologists
(vi) early morning, afternoon
(vii) Maximum-minimum thermometer
(viii) Weather
(ix) Climate
(x) Polar region, Tropical rainforest
In simple words: Weather changes daily, while climate is long-term atmospheric patterns.

Question Q2. Categorise places (polar/tropical) and animals (polar, tropical, migratory).
Answer:
(i) Polar regions: Canada, Greenland, Iceland, Norway, Alaska, Siberia.
Tropical rainforests: Indonesia, India, Congo, Kenya, Uganda, Nigeria.
(ii) Polar animals: Reindeer, Musk oxen, Seal, Whale.
Tropical animals: Lion, Red eyed frog, Beard ape, Snake, leopard, Elephant.
Migratory birds: Siberian crane, Arctic tern.
In simple words: Animals and locations are grouped by climatic zones and migratory behavior.

Question Q3 & Q4 & Q5 & Q6 & Q7. Fill in blanks, matching, polar bear/penguin adaptive features, tropical rainforest adaptations.
Answer:
Q3: (i) hot, wet (ii) adaptation (iii) huddle (iv) tropical rainforest (v) Western Ghats, Assam (vi) hot, humid.
Q4: Matching: (a)-(i), (b)-(v), (c)-(iv), (d)-(ii), (e)-(iii)
Q5 & Q6: Polar bear/Penguin: White fur/skin, thick fat layer (blubber), streamlined body, webbed feet, huddling.
Q7: Red eyed frog: Sticky pads on feet for climbing. Toucan: Long large beak to reach fruit on fragile branches. Big cats: Thick skin, sensitive hearing, sharp claws. Monkeys: Prehensile tails for grasping branches.
In simple words: Animals have evolved specialized physical and behavioral traits to survive in extreme climates.

Question Q1. Fill in the blanks: Inhalation/exhalation definition, yeast respiration, breath definition, diaphragm function, muscle cramp cause, cellular respiration definition, ATP/energy purpose, aerobic steps, human respiratory tract, exercise breathing rate.
Answer:
(i) inhalation, exhalation
(ii) single-celled / anaerobic, anaerobically (alcohol fermentation)
(iii) inhalation, exhalation
(iv) diaphragm
(v) Lactic acid accumulation
(vi) cellular respiration
(vii) energy, metabolic
(viii) Glycolysis (cytoplasm), Krebs cycle/ETC (mitochondria) [or simply presence of oxygen and breakdown]
(ix) nasal, windpipe (trachea), bronchi
(x) oxygen
In simple words: Respiration releases energy from food using oxygen (aerobic) or without oxygen (anaerobic).

Question Q2. Complete equations for cellular respiration: (i) Aerobic (ii) Anaerobic in muscles (iii) Anaerobic in yeast
Answer:
(i) Glucose \(\xrightarrow{\text{In presence of }\text{O}_2}\) Carbon dioxide + Water + Energy
(ii) Glucose \(\xrightarrow{\text{In absence of }\text{O}_2\text{ (in muscles)}}\) Lactic acid + Energy
(iii) Glucose \(\xrightarrow{\text{In absence of }\text{O}_2\text{ (in yeast)}}\) Alcohol + Carbon dioxide + Energy
In simple words: Glucose breaks down differently depending on oxygen availability, releasing energy in all cases.

Question Q3. Choose correct option: Cellular respiration breakdown products, slowest breathing rate case.
Answer:
(i) (d) CO\(_2\), energy & water
(ii) (c) Sleeping
In simple words: Aerobic breakdown yields carbon dioxide, water, and energy; resting slows down breathing.

Question Q4 & Q5 & Q6 & Q7 & Q8 & Q9. Breathing mechanism diagram questions, insect respiration, organ respiration list, inhaled/exhaled air percentages, plant breathing, aerobic vs anaerobic respiration table.
Answer:
Q4: (i) Mechanism of breathing (Inhalation & Exhalation). (ii) Figure A. (iii) C = Ribs, D = Lungs, E = Diaphragm. (iv) Table: Ribs move upward/outward vs downward/inward; Diaphragm moves downward vs upward; Chest cavity increases vs decreases; Air rushes in vs pushed out.
Q5: (i) Stomata (ii) Tracheae (iii) Insects (iv) Spiracles.
Q6: Cockroach-Tracheae, Earthworm-Skin, Human-Lungs, Fish-Gills, Whale-Lungs, Bird-Lungs, Snake-Lungs, Lizard-Lungs, Plant-Stomata/lenticels, Lion-Lungs.
Q7: Inhaled air: 21% O\(_2\), 0.04% CO\(_2\); Exhaled air: 16.4% O\(_2\), 4.4% CO\(_2\).
Q8: (i) oxygen, carbon dioxide. (ii) skin, lungs. (iii) oxygen, soil. (iv) milky, calcium carbonate.
Q9: Aerobic: Requires O\(_2\), complete breakdown, high energy. Anaerobic: No O\(_2\), partial breakdown, less energy.
In simple words: Different organisms use specialized respiratory organs suited to their habitats.

Question Q.1. Match the following (W.B.C, Veins, Haemoglobin, Stethoscope, Ventricles, Circulation, Plasma).
Answer:
(i) W.B.C. - (f) Fight germs
(ii) Veins - (d) CO\(_2\) rich blood
(iii) Haemoglobin - (b) Red pigment carrying oxygen
(iv) Stethoscope - (e) Heart beat amplification
(v) Ventricles - (a) Chambers of Heart
(vi) Circulation of blood - (c) William Harvey
(vii) Plasma - (g) Fluid part of blood
In simple words: Matching links blood components and cardiac terms with their biological functions.

Question Q2 & Q3 & Q4 & Q5 & Q6 & Q7 & Q8 & Q9 & Q10 & Q11 & Q12 & Q13. Fill in blanks, heart structure, blood composition table, artery vs vein differences, blood circulation flow chart, excretory system, xylem vs phloem transport.
Answer:
- Q2: Circulatory system consists of heart, blood vessels, blood. Three vessels: arteries, veins, capillaries. Blood consists of plasma, RBC, WBC, platelets.
- Q3: (i) Stethoscope (ii) Left side (iii) Blood (iv) Pulse.
- Q4 & Q5: Arteries carry oxygenated blood (except pulmonary artery) under high pressure with thick walls; Veins carry deoxygenated blood (except pulmonary vein) with valves and thin walls.
- Q6: Circulation flow: Body \(\rightarrow\) Vena Cava \(\rightarrow\) Right Atrium \(\rightarrow\) Right Ventricle \(\rightarrow\) Pulmonary Artery \(\rightarrow\) Lungs \(\rightarrow\) Pulmonary Vein \(\rightarrow\) Left Atrium \(\rightarrow\) Left Ventricle \(\rightarrow\) Aorta \(\rightarrow\) Body.
- Q8: Major excretory product in humans: Urea. Dialysis for artificial kidney. Excretory system: pair of kidneys, ureters, urinary bladder, urethra.
- Q11: (i) False (Xylem conducts water/minerals). (ii) True. (iii) False. (iv) True. (v) False.
- Q12: Xylem transports water and minerals upwards from roots to leaves; Phloem transports food bidirectionally from leaves to plant parts.
- Q13: Tissue definition, root hair function, vascular tissues, transpiration definition, suction pull.
In simple words: Animals use circulatory and excretory systems; plants use xylem and phloem for transport.

Question Q1. Fill in the blanks: Reproductive part, vegetative parts, vegetative propagation definition, leaf scar/node, bud types, fern/bread mold spores.
Answer:
(i) Flower
(ii) roots, stems, leaves
(iii) vegetative propagation
(iv) Node
(v) vegetative, bud
(vi) sori, sporangia
In simple words: Plants reproduce sexually through flowers and asexually through vegetative parts or spores.

Question Q2 & Q3 & Q4 & Q5 & Q6 & Q7 & Q8 & Q9 & Q10 & Q11 & Q12. Asexual methods, matching, table completion, fertilization steps, seed dispersal agents, plant types.
Answer:
- Q2: (i) Spirogyra: Fragmentation, (ii) Fern: Spore formation, (iii) Yeast: Budding, (iv) Bryophyllum: Leaf buds, (v) Potato: Tubers/eyes, (vi) Bread mould: Spores.
- Q6: (i) Papaya (unisexual), (ii) Sexual reproduction, (iii) Mustard (bisexual), (iv) Self pollination, (v) Cross pollination, (vi) Stamen.
- Q7: Fertilization: Pollen grain lands on stigma \(\rightarrow\) pollen tube grows through style \(\rightarrow\) male gamete fuses with female gamete (egg) in ovule to form zygote.
- Q8: Zygote develops into embryo, ovary develops into fruit, ovules develop into seeds.
- Q9: Animals (Xanthium), Wind (Maple/Drumstick), Water (Coconut), Explosive mechanism (Balsam/Pea).
- Q11: (i) Maple, (ii) Cotton/Madar, (iii) Sunflower, (iv) Sunflower/Hairy fruit.
In simple words: Plant reproduction involves pollination, fertilization, fruit/seed formation, and dispersal.

Question Q1. Fill in the blanks: Forest layers, ultimate food source, decomposer products, nutrient supply, interdependence, humus definition.
Answer:
(i) Tall trees (canopy), shrubs, herbs (understorey)
(ii) Plants
(iii) Nutrients / humus
(iv) nutrients
(v) food chain / web
(vi) Decomposers
(vii) Humus
In simple words: Forests maintain ecological balance through multi-layered vegetation, food chains, and nutrient recycling.

Question Q2 & Q3 & Q4 & Q5 & Q6 & Q7 & Q8 & Q9. Matching, decomposer examples, green lungs reasoning, water purification, flood/soil erosion prevention, global warming mitigation, absence of waste, forest disappearance consequences.
Answer:
- Q2: Matching: (a)-(iii), (b)-(iv), (c)-(v), (d)-(i), (e)-(ii)
- Q3: Decomposers: Bacteria, Fungi. Scavengers: Vultures, Crows, Jackals.
- Q4: Forests are called green lungs because they release oxygen and absorb carbon dioxide through photosynthesis.
- Q5: Forests prevent floods by slowing rainwater runoff and allowing ground infiltration; roots bind soil particles to prevent erosion.
- Q6: There is no waste in forests because dead matter is completely recycled into nutrients by decomposers and scavengers.
- Q9: If forests disappear: Oxygen levels drop, carbon dioxide and global temperatures rise, soil erodes leading to floods, and numerous animal/plant species face extinction.
In simple words: Forests are vital ecosystems acting as carbon sinks, water purifiers, and wildlife habitats.