Worksheet Solutions: Matter and its Composition | Chemistry Class 7 ICSE PDF Download

Part A: Multiple Choice Questions (MCQs)

Q1. Which of these proves that air is matter?
a) It has no colour
b) It occupies space
c) It has mass
d) Both (b) and (c)

Answer: d) Both (b) and (c)
Explanation: Air occupies space and has mass, as shown in balloon experiments, so it is matter.

Q2. In which state of matter are particles tightly packed with very little space?
a) Solid
b) Liquid
c) Gas
d) Plasma

Answer: a) Solid
Explanation: In solids, intermolecular forces are strongest, so particles are very close together.

Q3. Which of these is a compound?
a) Gold
b) Oxygen
c) Carbon dioxide
d) Sulphur

Answer: c) Carbon dioxide
Explanation: A compound is formed by chemical combination of two or more elements in fixed proportion. CO₂ has carbon and oxygen.

Q4. Which of these has no fixed shape or volume?
a) Solid
b) Liquid
c) Gas
d) All of these

Answer: c) Gas
Explanation: Gases expand to fill the container, so they have neither definite shape nor volume.

Q5. Which of these is not an element?
a) Iron
b) Sodium
c) Water
d) Sulphur

Answer: c) Water
Explanation: Water is a compound made of hydrogen and oxygen in a 2:1 ratio, not an element.

Part B: Short Answer Questions

Q6. Define matter with examples.
Answer:

• Matter is anything that has mass and occupies space.

• Examples: Rocks, water, air, humans, buildings.

Q7. Why can gases be compressed easily but not solids?
Answer:

• Gases have very large interparticle spaces, so their particles can be pushed closer.

• Solids have almost no interparticle space, so they cannot be compressed.

Q8. State two differences between solids and liquids.
Answer:

1. Solids have a definite shape; liquids do not — they take the shape of their container.

2. Solids are rigid and hard; liquids can flow because particles slide past each other.

Q9. What is an element? Give two examples.
Answer:

• An element is a pure substance that cannot be broken down into simpler substances.

• Examples: Iron, Gold.

Q10. What is the difference between an atom and a molecule?
Answer:

• Atom: The smallest unit of an element having all its properties (e.g., H, O).

• Molecule: A group of two or more atoms bonded together (e.g., H₂, O₂, CO₂).

Long Answer Questions

Q11. Explain the properties of solids, liquids, and gases with suitable examples.
Answer (Stepwise):

1. Solids

   • Have fixed shape, mass, and volume.

   • Particles are tightly packed with strong forces of attraction.

   • Cannot be compressed.

   • Example: stone, chalk, table.

2. Liquids

   • Have fixed volume but no fixed shape.

   • Particles are loosely packed, so they can flow.

   • Take the shape of the container.

   • Example: water, milk, juice.

3. Gases

   • Have neither fixed shape nor volume.

   • Particles are very far apart and move freely.

   • Can be easily compressed and expand to fill the container.

   • Example: oxygen, carbon dioxide, LPG.

Q12. Describe the particle theory of matter.
Answer (Stepwise):

1. All matter is made up of very small particles which cannot be seen with the naked eye.

2. These particles are held together by attractive forces called interparticle forces.

3. There is empty space between particles, called interparticle space.

4. The particles are always in motion; they vibrate, slide, or move freely depending on the state of matter.

5. Different substances have different kinds and sizes of particles.

Q13. Differentiate between elements and compounds with examples.
Answer (Stepwise):

1. Elements

   • Made up of only one kind of atom.

   • Cannot be broken down into simpler substances.

   • Example: gold, iron, sulphur, oxygen.

2. Compounds

   • Made up of two or more elements chemically combined in a fixed ratio.

   • Properties are different from the elements that form them.

   • Example: water (H₂O), carbon dioxide (CO₂), ammonia (NH₃).

3. Main Difference

   • Elements = pure single type of atom.

   • Compounds = fixed chemical combination of two or more elements.