ICSE Class 6 Chemistry Sample Paper with Solutions Set 02

Question 1

Choose the correct answer out of the four available choices given under each question. [15]

1. A glass tube made of pyrex is called a [1 Mark]
(a) Heating tube
(b) Boiling tube
(c) Melting tube
(d) Cracking tube

Answer: (b) Boiling tube

A glass tube made of Pyrex is called a boiling tube.

Teacher's Note:
a) Pyrex glass has high thermal resistance and can withstand sudden temperature changes.
b) Students must remember standard laboratory glassware terminology correctly.

2. Frost is the ___________ state of water. [1 Mark]
(a) Solid
(b) Liquid
(c) Gas
(d) Vapour

Answer: (a) Solid

Frost is the solid state of water formed by direct deposition of water vapour.

Teacher's Note:
a) Frost forms when water vapour turns directly into ice crystals without becoming a liquid first.
b) Pay close attention to different natural forms of water across states of matter.

3. Which of the following is a good conductor of heat? [1 Mark]
(a) Wood
(b) Rubber
(c) Cotton
(d) Copper

Answer: (d) Copper

Copper is a metal and hence it is a good conductor of heat. Wood, Rubber and Cotton are non-metals and bad conductors of heat.

Teacher's Note:
a) Metals generally possess free electrons that facilitate quick heat and electrical conduction.
b) Do not confuse thermal insulators like wood and rubber with metallic conductors.

4. The process of conversion of a liquid into a solid is called_______. [1 Mark]
(a) Melting
(b) Vaporisation
(c) Condensation
(d) Freezing

Answer: (d) Freezing

The conversion of a liquid into solid is called freezing. For example, conversion of water into ice.

Teacher's Note:
a) Freezing represents the phase transition from liquid to solid state upon cooling.
b) Ensure clear distinction between melting, freezing, and condensation processes.

5. During filtration, the substance left behind on the filter paper is called ____________. [1 Mark]
(a) Residue
(b) Filtrate
(c) Solution
(d) none of these

Answer: (a) Residue

During filtration, the substance left behind on the filter paper is called Residue.

Teacher's Note:
a) The clear liquid that passes through the filter paper is termed the filtrate.
b) Learn both terms associated with the filtration separation technique.

6. __________ is the representation of a substance by symbols. [1 Mark]
(a) Chemical formula
(b) Chemical structure
(c) Chemical equation
(d) Chemical reaction

Answer: (a) Chemical formula

Chemical formula is the representation of a substance by symbols.

Teacher's Note:
a) A chemical formula uses chemical symbols to show the elemental composition of a compound.
b) Do not confuse a chemical formula with a chemical equation, which represents an entire reaction.

7. Elements in compounds are present in ________ and cannot be separated by _________. [1 Mark]
(a) Definite proportion, physical methods
(b) Definite proportion, chemical methods
(c) Indefinite proportion, physical methods
(d) Indefinite proportion, chemical methods

Answer: (a) Definite proportion, physical methods

Elements in compounds are present in definite proportion and cannot be separated by any physical methods.

Teacher's Note:
a) Compounds have fixed composition by mass and require chemical methods to separate their constituents.
b) Mixtures have variable composition and can be separated by physical methods.

8. A separating funnel is used to separate ________. [1 Mark]
(a) Solid-liquid mixtures
(b) Solid-solid mixtures
(c) Liquid-liquid miscible mixtures
(d) Liquid-liquid immiscible mixtures

Answer: (d) Liquid-liquid immiscible mixtures

A separating funnel is used to separate liquid-liquid immiscible mixture. For example, mixture of oil and water, mixture of kerosene and water.

Teacher's Note:
a) Immiscible liquids form separate layers based on their densities.
b) Miscible liquids cannot be separated using a separating funnel and require distillation.

9. Nitrogen is necessary for [1 Mark]
(a) Photosynthesis
(b) Respiration
(c) Growth of plants
(d) Burning

Answer: (c) Growth of plants

Nitrogen is necessary for the growth and development of plants as it is a key component for plant proteins.

Teacher's Note:
a) Plants absorb nitrogen compounds from the soil to synthesize essential proteins.
b) Oxygen is required for respiration and burning, while carbon dioxide is needed for photosynthesis.

10. The % of water in human body is [1 Mark]
(a) 25%
(b) 50%
(c) 70%
(d) 90%

Answer: (c) 70%

Approximately 70% of the human body is composed of water.

Teacher's Note:
a) Water is essential for all metabolic and cellular activities in living organisms.
b) Keep standard biological percentages in mind for general science questions.

11. What is the percentage of carbon dioxide in air? [1 Mark]
(a) 0.02-0.03%
(b) 21%
(c) 78-79%
(d) Variable

Answer: (a) 0.02-0.03%

The percentage of carbon dioxide in air is 0.02-0.03%.

Teacher's Note:
a) Air is a mixture containing roughly 78% nitrogen, 21% oxygen, and small amounts of other gases including carbon dioxide.
b) Memorize the precise compositional breakdown of atmospheric air.

12. Which of the following is not a rare gas? [1 Mark]
(a) Argon
(b) Helium
(c) Krypton
(d) Hydrogen

Answer: (d) Hydrogen

Hydrogen is not a rare gas whereas, argon, helium and krypton are inert gases. This family of elements is also known as rare gases.

Teacher's Note:
a) Rare or noble gases include helium, neon, argon, krypton, xenon, and radon.
b) Hydrogen is a reactive diatomic non-metal, not a noble gas.

13. Drinking polluted water causes ________. [1 Mark]
(a) Jaundice
(b) Polio
(c) Tuberculosis
(d) Cancer

Answer: (a) Jaundice

Drinking polluted water causes water-borne diseases such as Jaundice.

Teacher's Note:
a) Water pollution introduces harmful pathogens that lead to diseases like jaundice, cholera, and typhoid.
b) Differentiate between water-borne and air-borne diseases.

14. Heterogeneous solid-liquid mixtures can be separated using _________. [1 Mark]
(a) Sublimation
(b) Boiling
(c) Decantation
(d) Distillation

Answer: (c) Decantation

Heterogeneous solid-liquid mixtures can be separated using decantation or filtration.

Teacher's Note:
a) Decantation involves pouring out liquid carefully after insoluble particles settle down.
b) Distillation is used for homogeneous solutions or liquid-liquid mixtures.

15. Cream is separated from milk by _________ . [1 Mark]
(a) Winnowing
(b) Evaporation
(c) Filtration
(d) Distillation

Answer: (d) Distillation / (c) Filtration / Centrifugation
*(Note: The official marking scheme mentions Option (b) Filtration as per answer key text, but scientifically cream is separated from milk by centrifugation. We record the standard answer key option while noting the scientific correction.)*

Teacher's Note:
a) The official key lists filtration, but centrifugation is the actual industrial and laboratory method used to separate cream from milk.
b) Students should note this discrepancy in standard textbook question banks .

Question 2

(A) Define the following: [5 Marks]
1. Valency
2. Diatomic molecule
3. Weathering
4. Condensation
5. Intermolecular force

Answer:
1. Valency of an element is the number of hydrogen atoms which can combine with one atom of the element to form a compound.
2. A molecule is diatomic when it contains two atoms.
3. Wind, rain, heat and frost result in the breaking up of large rocks leading to the formation of soil. This process is called weathering.
4. The process of changing of gas or vapors into liquid by cooling is called as condensation.
5. The force of attraction between molecules is called Intermolecular force.

Teacher's Note:
a) Ensure exact definitions are memorized for fundamental chemical terms.
b) Watch out for accurate spelling and scientific keywords like 'attraction' and 'vapours'.

(B) Fill in the blanks and rewrite the sentences: [5 Marks]
1. A molecule of nitrogen consist of ____________ atoms of element nitrogen only.
2. A compound is formed by combination of at least _________ elements.
3. In solids, the molecules are __________.
4. ____________ retain their shape.
5. Water is __________ .

Answer:
1. A molecule of nitrogen consist of two atoms of element nitrogen only.
2. A compound is formed by combination of at least two elements.
3. In solids, the molecules are closely packed up.
4. Solids retain their shape.
5. Water is a compound.

Teacher's Note:
a) Fill in the blanks require complete sentence rewriting as per instructions.
b) Verify each term against standard states of matter and atomic theory.

Question 3

(A) State a method to separate the following mixtures: [5 Marks]
1. Separating stone particles from wheat grains
2. Separating heterogeneous solid-liquid mixtures
3. Separating saw dust from water
4. Separating mixture of oil and water
5. Separating cream from milk

Answer:
1. Handpicking
2. Decantation (or Filtration)
3. Filtration
4. Separating funnel
5. Centrifugation

Teacher's Note:
a) Choose separation techniques based on the physical properties of components in the mixture.
b) Handpicking is suitable for large impurities, whereas filtration handles insoluble fine particles.

(B) Write a note on the water cycle. Explain it with the help of a diagram. [5 Marks]

[Figure: Schematic diagram of the water cycle showing ocean evaporation, water vapour rising, cloud formation, precipitation as snow and rain, surface runoff, infiltration, and groundwater flow.]

Answer:
The water cycle is a natural cyclic process in which water is transferred from the Earth's surface to the atmosphere and back to the Earth's surface.
Heat from the Sun causes water to evaporate and rise from the seas, rivers and other water bodies and results in the formation of water vapour. As the water vapour rises, it condenses into small droplets of water, resulting in the formation of clouds. When the size of the water droplets in the clouds increases, they fall down in the form of rain. The rain water is collected underground and is streamlined into streams and ponds. Stream water enters the rivers, seas or oceans. The water from the sea evaporates forming clouds and thus continues the water cycle.

Teacher's Note:
a) Describe evaporation, condensation, and precipitation sequentially to explain the water cycle.
b) Diagrams should be neatly labelled showing arrows for evaporation and precipitation.

Question 4

(A) Give the principle and working of sublimation with an example. [5 Marks]

[Figure: Sublimation apparatus setup showing an evaporating dish with non-sublimable particles, covered by an inverted glass funnel plugged with cotton at the stem, with sublimable particles condensed on the inner sides.]

Answer:
Principle of sublimation: Sublimation is based on the difference between the sublimable and non-sublimable nature of solids.
Working: A mixture of sublimable and non-sublimable substances is placed on an evaporating dish which is covered with an inverted flask plugged with cotton. On heating, the sublimable component evaporates and further condenses on the sides of the flask and the non-sublimable component remains in the evaporating dish.
Example: Sublimation can be used for the separation of ammonium chloride and sodium chloride in the laboratory.

Teacher's Note:
a) Sublimation is the direct conversion of a solid into vapour on heating without passing through the liquid state.
b) Mention ammonium chloride and camphor as classic examples.

(B) Answer the following: [5 Marks]
1. Distinguish between element and compound.
2. Distinguish between physical and chemical changes.

Answer:
1. Distinction between element and compound:

Example: C + O₂ → CO₂. Carbon and oxygen have their own set of physical and chemical properties. But carbon dioxide compound formed from the combination of these two elements has altogether different physical and chemical properties from these two elements.

2. Distinction between physical and chemical changes:

Teacher's Note:
a) Always present comparative answers in a tabular format for clarity.
b) Emphasize that chemical changes result in new substances with different chemical properties.

Question 5

(A) State which of the following statements are false. Rewrite the correct statements, if false: [5 Marks]
1. Air is all around.
2. Air cannot be compressed.
3. Nitrogen is the major component of air.
4. Aquatic animals do not breathe the air dissolve in water.
5. All living organisms breathe air to remain alive.

Answer:
1. True
2. False. Air can be compressed.
3. True.
4. False. Aquatic animals breathe the air dissolved in water.
5. True.

Teacher's Note:
a) Read each statement carefully to check scientific accuracy.
b) Ensure false statements are corrected properly without altering their core meaning.

(B) Match the important chemical compounds in Column A with its uses in column B. [5 Marks]

Answer:
1. Fertilisers - help in improving soil's fertility
2. Insecticides - help in killing insects that infect and destroys crops
3. Fungicides - help in destroying fungi that destroys crops
4. Herbicides - help in killing weeds which grows along with the crops
5. Pesticide - help in killing pests like rats, snakes etc. which destroys the crop

Teacher's Note:
a) Match agricultural chemicals with their specific target organisms.
b) Notice that herbicides target weeds while insecticides target insect pests.

Question 6

(A) Describe a burette, wire-gauze and test tube. Give their uses. [5 Marks]

Answer:
Burette: A burette is a uniform-bore glass tube with fine graduations and a tap at the bottom. It is used for accurately fluid dispensing and measurement.
Wire-gauze: A wire-gauze is a rectangular wire mesh with asbestos at its centre. It prevents the cracking of glass apparatus during heating. It also helps in uniform distribution of heat.
Test tube: A test tube is a special glass tube with one open and one closed end. It is used for heating purposes and also for mixing liquids during chemistry experiments.

Teacher's Note:
a) Describe laboratory apparatus with emphasis on their structural features and practical applications.
b) Mention the role of asbestos in wire-gauze for heat distribution.

(B) Write the techniques used for separating the following mixtures: [5 Marks]
1. Husk and wheat
2. Pebbles from pulses
3. Pure copper sulphate from impurities
4. Sugar from sugar solution
5. Pure water from impure water

Answer:

Teacher's Note:
a) Match separation techniques precisely to the physical state and properties of the mixtures.
b) Crystallization is ideal for obtaining pure soluble solids from solutions.

Question 7

1. Write a note on the structure of atom. [4 Marks]

[Figure: Diagram of an atom showing a central nucleus containing protons (+) and neutrons (neutral), surrounded by orbits/shells with revolving electrons (-).]

Answer:
- An atom is the smallest particle of an element.
- An atom consists of three particles namely- protons, electrons and neutrons.
- Protons are positively charged and are found at the center in the nucleus of the atom.
- Neutrons are neutral in charge and are also found at the center in the nucleus of the atom.
- Electrons are negatively charged and they revolve around the nucleus in circular orbits.

Teacher's Note:
a) State the three subatomic particles along with their charges and locations clearly.
b) Emphasize that the nucleus contains protons and neutrons while electrons revolve outside.

2. Nitrogen present in the air is essential for the growth and development of plants. Give reason. [3 Marks]

Answer:
Air consists of 78-79% of nitrogen. Some of the nitrogen present in the air is converted into soluble nitrogenous compounds in the soil, in the presence of moisture and air. These compounds are then absorbed by plants and converted into plant proteins. These proteins are essential for plants growth and development. Therefore, nitrogen present in the air is essential for the growth and development of plants.

Teacher's Note:
a) Explain nitrogen fixation and its conversion into plant proteins for growth.
b) Highlight that plants cannot use atmospheric nitrogen directly without fixation.

3. State the characteristics of states of matter [3 Marks]

[Figure: Particle arrangement diagrams for Solid State (closely packed regular grid), Liquid State (slightly spaced sliding particles), and Gaseous State (widely separated random particles).]

Answer:

Teacher's Note:
a) Compare states of matter based on inter-particle space, intermolecular force, and rigidity/shape.
b) Use neat comparative tables to secure full marks in descriptive state-of-matter questions.