Class 9 Science Chapter 1 Question Answers - Matter in Our Surroundings

Q1: A rubber band is a solid, but it can change its shape. Why?
Ans: A rubber band changes shape under force and regains the shape when the force is removed, this is due to less intermolecular force of attraction between the particles.

Q2: When salt or sugar is poured into different kinds of vessels, why do they take the shape of vessel as they are solid?
Ans: Salt or sugar takes the shape of containing vessel, but does not change its individual shape. For example : Sugar crystal is cubical and they remain cubical in any vessel.

Q3: We can easily move our hand in the air but to do the same through a solid block of wood. We need a karate expert. Why?
Ans: In air, the inter-particle attractive forces are negligible and hence, it is easy to separate the particles in air and we can easily move our hand in air. The interparticle forces are very strong in solids. So, it is not easy to separate the particles and it is not easy to move our hand through a solid block of wood.

Q4: Express the boiling point of water in Celsius as well as Kelvin scale.
Ans: 100°C and 373 K.

Q5: What is dry ice?
Ans: Solid carbon dioxide obtained by cooling and applying pressure on carbon dioxide gas. It does not melt so it is called dry ice.

Q6: What is normal atmospheric pressure?
Ans: The atmospheric pressure at sea level is 1 atmosphere and taken as the normal atmospheric pressure.

Q7: Give the temperature at which water exists in two different phases/states.
Ans: (i) At 0°C water can be in solid or in liquid state. (ii) At 100°C water can be in liquid or in gaseous state.

Q8: Define matter.
Ans: Anything that occupies space and has mass and is felt by senses is called matter.

Q9: Give state of a matter if this substance has neither a fixed shape nor a fixed volume.
Ans: Gas.

Q10: What do you mean by vapour?
Ans: A substance that is found in gaseous state only at room temperature is called vapour.

Q11: Name any two substances which sublime.
Ans: Camphor and naphthalene.

Q12: Which is the slow process, evaporation or boiling?
Ans: Evaporation.

Q12: Write the SI unit of temperature?
Ans: Kelvin.

Q13: Convert 10°C into Kelvin scale.
Ans: 273 + 10 = 283 K

Q14: Name two processes from which it may be concluded that the particles of a gas move continuously.
Ans: Compressibility and Brownian movement.
Q15: What is common among the three states of matter?
Ans: They all contain molecules.

Q16: A substance x is highly compressible and could easily be liquefied. It can also take the shape of the container. Guess the nature of the substance.
Ans: Gas.

Q17: Is it possible to turn a liquid into vapour without heating?
Ans: Yes, by the process of evaporation as evaporization of water occur below the boiling point under atmospheric pressure.

Q18: When we put CuSO4 in water, after some time we find the solution turns blue. Why? Also, on heating it, what change will occur?
Ans: The solution turns blue because of diffusion. On heating the solution, nothing will happen.

Q19: The boiling point of alcohol is 78°C. What is this temperature on Kelvin scale?
Ans: K = °C + 273 = 78 + 273 = 351 K

Q20: Why are light and sound not considered as matter?
Ans: Light and sound are not considered as matter because they have no mass and do not occupy space.

Q21: We can get the smell of perfume sitting several metres away, why?
Ans: This is because perfumes diffuse very fast and can reach to people sitting several metres away.
Q22: Sponge is a solid, yet we are able to compress it. Why?
Ans: Sponge has very small holes throughout its structure. These holes are filled with air. When it is compressed, the air in the holes is squeezed out. Thus, we are able to compress it.

Q23: What is plasma?
Ans: Plasma is a state of matter consisting of super excited particles of very high energy level.

Q24: Define melting point.
Ans: The temperature at which a solid melts to become liquid at the atmospheric pressure is called its melting point.

Q25: What is humidity?
Ans: The air holds water vapour, this air with water is called humid air and the amount of water vapour present in the air is called humidity.