Grade 9 Science Chapter 1 - Matter in Our Surroundings

Grade 9 Science 

Chapter 1 - Matter in Our Surroundings

Q1. Define matter.

Answer: Anything that occupies space and has mass is called matter.

Q2. What are the characteristics of particles of matter?

Answer: The characteristics of particles of matter are:

(i) Particles of matter have space between them.

(ii) Particles of matter are continuously moving.

(iii) Particles of matter attract each other.

Q3. What is meant by the term 'inter-particle space' and 'inter-particle attraction'?

Answer: Inter-particle space refers to the space between particles of matter. Inter-particle attraction refers to the force of attraction between particles of matter.

States of matter:

(i) Define the term 'solid.'

Answer: Solid is a state of matter in which the constituent particles are tightly packed, have fixed shape and volume, and cannot be compressed easily.

(ii) Define the term 'liquid.'

Answer: Liquid is a state of matter in which the constituent particles are close together but not rigidly held, have no fixed shape but fixed volume, and cannot be compressed easily.

(iii) Define the term 'gas.'

Answer: Gas is a state of matter in which the constituent particles are far apart, have no fixed shape or volume, and can be compressed easily.

Q. Can we change the state of matter? If yes, how?

Answer: Yes, we can change the state of matter by changing the temperature and pressure. For example, by increasing the temperature and decreasing the pressure, we can convert a solid into a liquid and a liquid into a gas.

Q. Can you classify the following as solids, liquids or gases?

(i) Oxygen

Answer: Gas

(ii) Mercury

Answer: Liquid

(iii) Carbon dioxide

Answer: Gas

(iv) Iodine

Answer: Solid

Q. Why does a gas exert pressure?

Answer: A gas exerts pressure because its particles are in constant random motion and collide with the walls of the container, exerting a force on them.

Q. The boiling point of water at standard atmospheric pressure is 100°C. Why does the temperature of water remain constant at 100°C during boiling?

Answer: The temperature of water remains constant at 100°C during boiling because the heat energy supplied to it is used to overcome the inter-particle attraction between water molecules and convert it into steam.

Q. Why do we feel cool under a fan?

Answer: We feel cool under a fan because it increases the rate of evaporation of sweat from our skin. When sweat evaporates, it takes away some heat energy from our body, making us feel cool.

Q. What is sublimation? Give an example.

Answer: Sublimation is the process of conversion of a solid directly into a gas on heating without passing through the liquid state. An example of sublimation is the conversion of camphor into a gas on heating without melting.

MCQs

Q. Which of the following is a characteristic of particles of matter?

a) Particles of matter are not in motion

b) Particles of matter do not have any space between them

c) Particles of matter do not attract each other

d) Particles of matter are continuously moving

Answer: d) Particles of matter are continuously moving

Q. Which of the following is a property of a solid?

a) Fixed volume but no fixed shape

b) No fixed shape or volume

c) No inter-particle attraction

d) Fixed shape and volume

Answer: d) Fixed shape and volume

Q. Which state of matter has the most inter-particle space?

a) Solid

b) Liquid

c) Gas

d) None of the above

Answer: c) Gas

Q. Which of the following is not an example of sublimation?

a) Conversion of solid carbon dioxide into gas

b) Conversion of solid iodine into gas

c) Conversion of solid sodium chloride into gas

d) Conversion of solid camphor into gas

Answer: c) Conversion of solid sodium chloride into gas

Q. Why do we feel cool under a fan?

a) The fan lowers the temperature of the air

b) The fan increases the temperature of the air

c) The fan increases the rate of evaporation of sweat from our skin

d) The fan decreases the rate of evaporation of sweat from our skin

Answer: c) The fan increases the rate of evaporation of sweat from our skin

Q. Which of the following is not a state of matter?

a) Plasma

b) Bose-Einstein condensate

c) Solidus

d) All of the above are states of matter

Answer: c) Solidus

Q. Which of the following is a property of a liquid?

a) No fixed shape but fixed volume

b) Fixed shape and volume

c) Fixed shape but no fixed volume

d) No fixed shape or volume

Answer: a) No fixed shape but fixed volume

Q. Which of the following states of matter has the strongest inter-particle attraction?

a) Solid

b) Liquid

c) Gas

d) All have equal inter-particle attraction

Answer: a) Solid

Q. Which of the following is not an example of a gas?

a) Oxygen

b) Water vapor

c) Carbon dioxide

d) Mercury

Answer: d) Mercury

Q. What is the boiling point of water at standard atmospheric pressure?

a) 0°C

b) 50°C

c) 100°C

d) 150°C

Answer: c) 100°C