Worksheet solutions for chapter: Matter in Our Surroundings for class 9 are provided below.
(1) Radha saw frost on the window in winter. Explain the phenomenon.
Ans – Radha saw frost on the window in winter because of deposition. The cool air of outside the home comes in contact of window and changes in to solid matter (Frost) with out changing in to liquid state.
(2)We apply ice or cold water when we get burn on our skin. Why?
Ans- We apply ice or cool water when we get burns on our skin because our ice of cool water takes out energy from our burnt skin and we feel cool.
(3)A glass is half filled with water. Identify the different state of matter (including glass).
Ans- The different states of matter are –
(a) Glass – solid
(b) Water – Liquid
(c) Air filled in half glass – Gaseous
(4) Raja is boiling water and put lid on the pot. After some time he find few drops on the lid. Write down the change of state of matter at different stages of work.
Ans- (a) When water starts boiling – Water changes to gaseous
(b) Few drops on lid – Gaseous state changes to liquid state
(5) Write the factors affecting evaporation.
Ans- Factors affecting evaporation
(i) Increased surface area can increased the process of evaporation.
Eg :- We spread wet clothes for drying. Therefore, surface area of the cloth increased which increases the processes of evaporation.
(ii) Increase of temperature can increase the temperature of the process of the evaporation.
Eg :- Preparing tea. In the process of preparing tea, kinetic energy of liquid increases with the increase of the temperature of the liquid. As a result, force of attraction loosens up and particles of the liquid leave surface as vapour.
(iii) A decrease in humidity-
Humidity is the amount of the water that is present in the air.
If the amount of water or humidity is already high evaporation will be slow because air can hold definite amount of water.
(iv) Increase in wind speed also help in evaporation because water particles in air moves with air. Therefore, the air surrounds us have little water and evaporation become faster to compensate water level.
Eg:- Clothes dry faster in high wind speed.
(6) Rani spread clothes to dry in open. She felt that clothes become dry in summer rather than rainy season. Give reason.
Ans- In summer humidity is very low which increases process of evaporation of water. But humidity is very high in rainy season which slow down the evaporation. Therefore, clothes become dry in summer rather than rainy season.
(7) Write the difference between latent heat of fusion and latent heat of vaporisation.
Ans- The differences between latent heat of fusion and latent heat of vaporisation are tabulated below-
|Characteristics||Latent heat of fusion||Latent heat of vaporisation|
|Change of state of matter||Required to change 1 kg of solid in to liquid||Required to change 1 kg of liquid into gas|
|Temperature||Melting point of solid||Boiling point of liquid|
|Examples||Ice melted in to water||Water vaporised in to steam|
(8) Write down the differences between sublimation and deposition.
Ans- The differences between sublimation and deposition are tabulated below-
|Change of state of matter||Solid to gaseous state without changing in to liquid||Gaseous to solid without changing in to liquid.|
|Temperature||Happens in increasing temperature||Happens in decreasing temperature|
|Examples||Naphthalene balls disappear||Frost deposited on windows in winter|
(9) Convert the following temperatures to the Celsius scale-
(a) 273 K (b) 500 K
(a) T K= T 0C + 273K
273 K = T 0C + 273K
T 0C = 273K– 273K
Hence, 273K is equal to 00C.
(b) T K = T 0C + 273K
500 K = T 0C + 273K
T 0C = 500K – 273K
Hence, 500K is equal to 2270C.
(10) Identify the state of matter and give reason in sport of your answers.
(a) Gaseous matter because particles are very far to each other.
(b) Solid because particles are very close to each other.