Sound Class 9 Science Worksheet Pdf
Class 9 Science students should refer to the following printable worksheet in Pdf for Sound in standard 9. This test paper with questions and answers for Grade 9 Science will be very useful for exams and help you to score good marks
Class 9 Science Worksheet for Sound
1 Mark Questions:
1.On the basis of Thomson’s model of an atom, explain how the atom is neutral as a whole?
2.Where are electrons found in the atom?
3. What are canal rays?
3.Why is the nucleus of an atom positively charged?
4.Why did Rutherford select a gold foil in his α-ray scattering experiment?
5. If Mg2+has 12 protons and 12 neutrons,what is its atomic number and mass number? (CBSE 2010)
6.What are the limitations of Rutherford's model of the atom?
7.Define valency and Give an example of a monovalent element.
8.An atom of an element has 7 electrons in its L shell,name the element and write it's atomic number?
9.Why Mg atom gets 2+ charge when it loses two electrons ?
10.Name the particles which determine the mass of an atom.
11.Which of the following are isotopes and which are isobars? Argon, Protium, Calcium, Deuterium.
2 Mark Questions:
1.What observations in a scattering experiment led Rutherford to make the following observations:
i) Most of the space in an atom is empty.
ii) Nucleus is positively charged.
iii)Whole mass of an atom is concentrated in its centre.
2.Mention any two drawbacks of Rutherford’s model.
3. State the characteristics of nucleus of an atom.
4. Describe Bohr’s model of the atom?
5.The atomic number of chlorine is 17 and mass number is 35.
a. What would be the electronic configuration of a negatively charged chloride ion, Cl- ?
b. What would be the atomic number and mass number of Cl- ?
6.What is electronic configuration and how is the valency of an atom related to it ?
7.Which of the two would be chemically more reactive element,X of atomic number 18 or element Z of atomic number 16 and why?
8.What are isotopes? Why do isotopes show similar chemical properties but they differ in physical properties?
9.Write isotopes of uranium and its uses.
10.Write one pair of Isobars. Why the chemical properties of isobars are not similar?
3 Mark Questions:
1. Explain Rutherford's gold foil experiment with diagram
2.Write three points of difference between isotopes and isobars.
3.The average atomic mass of a sample of an element ‘X’ is 16.2μ. What is the percentage of each isotope 16X and 18X in the sample?( At.No. of X =8)
4.Define valency of an element. Find the valency of chlorine and magnesium.
5.i)What is the similarity in the electronic structure of the following set of atoms? Lithium, sodium and potassium.
ii) Which of the above element is most reactive and why?
6.Complete the following table.
Element At. No. Mass No. Protons Neutrons Electrons
A 11 - - 12 -
B - 35 - - 17
C - - 9 10 -
D - 20 - - 10
7.Give reason for the following
a) An atom is electrically neutral
b) Noble gases show least reactivity
c) Nucleus of an atom is heavy and positively charged.
d) Ions are more stable than atoms.
8. An element has an atomic number 12 and mass number 26.Draw a diagram showing the distribution of electrons in the orbits and the nuclear composition of the neutral atom. If this element X combines with another element Y whose electronic configuration is 2,8,7, what will be the formula of the compound thus formed? (CBSE CCE 2010)
9. Name the Scientists who have contributed the following towards the understanding of the atomic structure.
i) Discovery of electrons
ii) Canal rays
iii) Concept of nucleus
iv) Stationary orbits
v) Indivisibility of atoms
Value Based Question :
1.In Kaiga nuclear Power Corporation building,drinking water was found to be contaminated with tritium .
It is highly radioactive.
a) What is tritium? Write its atomic number and mass number.
b) It is an isotope of which element?
c) Name the other two isotopes of the same element.
d) What precautions do you suggest so that this type of incident does not occur again?
e) What is meant by radioactive?
2. Most of the children burst crackers during diwali.It creates a lot of noise pollution and air pollution. Asthma patients have tough time during diwali.Many children get hurt due to mishandling of fire crackers.Poisonous gases like sulphur dioxide ,phosphorous pentoxide are formed.
a) Name two elements present in gun powder used in crackers.
b) Government has banned bursting of fire crackers after 10pm.Do you agree? Give reason.
c) Why should we not wear synthetic clothes while bursting crackers?
Exam Questions NCERT Class 9 Science Chapter 12 Sound
Question. Do waves transport matter?
Ans : No.
Question. Sound is produced due to a vibratory motion, then why a vibrating pendulum does not produce sound?
Ans : The frequency of the vibrating pendulum does not lie within the audible range (20 Hz to 20,000 Hz) and hence, it does not produce audible sound.
Question. Why do echoes produced in an empty auditorium usually decrease when it is full of audience?
Ans : When the hall is empty there are no obstacles in between to reflect the sound other than the walls.
When the hall is full of audiences, the sound produced undergoes multiple reflections from the people and so it overlaps with the sound produced. Hence, the listener is not able to distinguish between the original sound and the echo.
Question. What is a wave?
Ans : A wave is a disturbance that travels in a medium due to repeated periodic motion of particles about their mean position – such that the disturbance is handed over from one particle to the other without the actual motion of the medium.
Question. What is a transverse wave?
Ans : It is a wave in which the particles of the medium vibrate perpendicular to the direction of propagation of the wave.
Question. What is a longitudinal wave?
Ans : It is a wave in which the particles of the medium vibrate in the direction of propagation of the wave.
Question. What do you understand by the term ultrasonic vibrations?
Ans : Sounds of frequency higher than 20,000 Hz are called the ultrasonics.
Question. What do you understand by the term echo?
Ans : The sound heard after reflection from a rigid obstacle is called an echo.
Question. Do the particles of the medium move from one place to another in a medium?
Ans : No.
Question. Does the velocity of wave motion depend on the nature of the medium?
Ans : Yes.
Question. Does the velocity of wave motion depend on the nature or motion of the source?
Ans : No.
Question. What are transverse waves? Give two examples.
Ans : A wave in which the particles of the medium vibrate up and down at right angle to the direction in which the wave is moving.
Example : (i) The waves produced by moving one end of a long spring up and down rapidly.
(ii) Ripples formed on the surface of water in a pond.
Question. What are crests and troughs of a wave?
Ans : The elevation in a transverse wave is called crest. It is that part of transverse wave which s above the line of zero disturbance of the medium. The depression in a transverse wave is called trough. It is that part of the transverse wave which is below the line of zero disturbances.
Question. A Sitarist tries to adjust the tension and pluck the string suitably, before playing the orchestra in a musical concert. By doing so what is he adjusting?
Ans : He is adjusting frequency if the sitar string with the frequency of the other musical instrument.
Question. If the tension in the wire is increased four times, how will the velocity of wave in a string varies?
Ans : Velocity of the wave in string is directly proportional to the square root of the tension thus if tension is increased 4 times, the velocity will be doubled.
Question. Explain, how is the principle of echo used by the dolphin to locate small fish as its prey?
Ans : Dolphins are aquatic animals which send out ultrasonic sound to communicate with each other. They have a sound sensing system which enables them to find animals underwater with great accuracy due to the echo of the ultrasonic sound produced by them.
Question. Give two practical applications of the reflection of sound waves.
Ans : (i) In stethoscope the sound of patient’s heartbeat reaches the doctor’s ears by multiple reflections in the tubes.
(ii) Megaphones are designed to send sound waves in particular direction are based on the reflection of sound
Question. What is the other name of a long flexible spring?
Ans : Slinky is the other name of a long flexible spring.
Question. Distinguish between tone and note.
Ans : A pitch is a particular frequency of sound, for example : 440 Hz.
A note is a named pitch. For example : Western music generally refers to the 440 Hz pitch as A, specifically A4.
Question. How do you account for the fact that two strings can be used to give notes of the same pitch and loudness but of different quality?
Ans : The ‘quality’ of a given note is determined by the overall effect of the harmonics present in it. The harmonics are multiples of the fundamental or basic frequency of the ‘note’. Depending on the conditions under which vibrations are taking place, sometimes we get one set of harmonics and sometimes another set.
The quality of the two notes will, therefore, different even though their fundamental frequencies may be the same.
Question. Can you produce both types of waves (i.e., longitudinal and transverse) on a slinky?
Ans : Yes, we can produce both types of waves (i.e., longitudinal and transverse) on a slinky.
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