Extra Questions for Class 9th: Ch 1 Matter in Our Surrounding (Science) Important Questions Answer Included
Very Short Answer Questions (VSAQs): 1 Mark
Q1. Sponge is a solid yet we are able to compress it. Why?
Answer
There are minute holes in sponge in which air is trapped which is expelled out when compressed. Thus, sponge is compressible.
Q2. Define Condensation.
Answer
The change of solid state from liquid state on cooling is also known as Condensation.
Q3. At which the solid and liquid states of substance can exist together?
Answer
0°C
Q4. Identify the name of the material which has no fixed shape but a fixed volume : Wood, a piece of iron, oxygen and water.
Answer
Water
Q5. What is the effect of pressure on boiling point?
Answer
Boiling point increases with increase in pressure.
Short Answer Questions-I (SAQs-I) : 2 Marks
Q1. Camphor disappears without leaving any residue. Explain?
Answer
Camphor disappears without leaving any residue because of sublimation, as it changes its state directly from solid to gas without changing to liquid.
Q2. Compare the rate of diffusion of liquids and solids with reason.
Answer
(i) Rate of diffusion of liquids is higher than solid because the particles of liquid can move freely.
(ii) Particles of liquid have greater spaces between them than solids. Thus, diffusion takes place easily.
Q3. Write the chemical name of dry ice. Justify its name. How it is stored ?
Answer
Chemical name of dry ice is solid CO2.
Solid CO2 gets converted directly to gaseous state on decreasing the pressure to 1 atmosphere without coming into liquid state. Therefore, it is known as dry ice.
It is stored at high pressure.
Q4. Arrange the three states of matter in the increasing order of:
(i) rate of diffusion
(ii) particle motion.
Answer
(i) Rate of diffusion: solid < liquid < gas.
(ii) Particle motion: solid < liquid < gas
Q5. Mention two properties of water to justify that water is liquid at room temperature.
Answer
Water is liquid at room temperature because:
(i) It takes the shape of the container in which it is kept.
(ii) It can flow or shows fluidity.
Short Answer Questions-II (SAQs-II) : 3 Marks
Q1. Explain why heat energy is needed to melt a solid. Define latent heat of fusion.
Answer
Heat energy is needed to melt a solid because there exist forces of attraction between the particles of solid. The heat energy helps in overcoming the forces of attraction between the particles and thus helps in melting a solid.
Latent heat of fusion is the amount of heat energy required to change 1 kg of solid into liquid at atmospheric pressure at its melting point.
Q2. An inflated air balloon deflates when pricked with a pin. Which property of the gaseous state is shown?
Answer
An inflated air balloon deflates when pricked with a pin due to the property of diffusion in gases. The molecules in a balloon are under higher pressure and the particles of gases are closely packed. When a pin is pricked on the surface of balloon, the diffusion from inside to outside takes place which is very fast process and hence the balloon deflates.
Q3. Why does the temperature remain constant during the change of state of matter? Explain it on the basis of change of solid state into liquid state.
Answer
The temperature remains constant as the heat gets used up in changing the state by overcoming the forces of attraction between the particles.
For example, a solid melts on heating. Its temperature does not rise until the entire solid is converted into liquid. This heat energy gets hidden into the contents and is known as the latent heat.
Long Answer Questions (LAQs) : 5 Marks
Q1. List any four factors on which evaporation depends. Explain in short any three factors.
Answer
The rate of evaporation depends on following factors:
(i) Surface area exposed to atmosphere
(ii) Temperature
(iii) Humidity
(iv) Wind speed
(i) Surface area exposed to atmosphere: Since evaporation is a surface phenomenon, therefore, it increases with an increase in surface area.
(ii) Humidity: The air around us cannot hold more than a definite amount of water vapour at a given temperature. If the amount of water in air is already high, the rate of evaporation decreases. So, evaporation decreases with increase in humidity.
(iii) Wind speed: With the increase in wind speed, the particles of water vapour move away with the wind, decreasing the amount of water vapour in the surroundings. This results in a faster rate of evaporation. So, evaporation increases with the increase in wind speed.
Q2. (a) Arrange the following matters in the increasing order of
(i) force of attraction
(ii) intermolecular space:
Matters: iron nail, kerosene and oxygen gas.
(b) Define the following terms:
(i) Rigidity, (ii) Compressibility, (iii) Diffusion.
Answer
(a) (i) Force of attraction: Oxygen gas < Kerosene < Iron nail
(ii) Intermolecular space: Iron nail < Kerosene < Oxygen gas
(b) (i) Rigidity: It is the property of matter to maintain shape against external force.
(ii) Compressibility: It is the property of matter by virtue of which molecules of matter are brought closer to each other.
(iii) Diffusion: The inter mixing of the particles of matter is known as diffusion.