give some important extra questions for ch 1 matter in our surroundings chemistry class 9 with answer
Answers
Answer:
Question 1.
A rubber band can change its shape on stretching. Will you classify it as solid or not? Justify?
Answer
Rubber band changes shape under force and regains the shape when the force is removed. So, it is classified as a solid.
Question 2.
Sponge, though compressible, is a solid?
Answer
A sponge has minute holes in which air is trapped. When we press it, the air is expelled out and we are able to compress it. On releasing pressure, it again regains its shape. So, it is classified as a solid.
Question 3.
Gases completely fill the vessel in which they are kept. Give reasons.
Answer
In the gaseous state, particles move freely and have greater space between them. So they occupy the entire space available. Hence, gases completely fill the vessel in which they are kept.
Question 4.
Under what conditions gases can be liquefied? In which form LPG is filled in gas cylinder?
Answer
By applying pressure and reducing temperature, gases can be liquefied. The liquefied petroleum gas (LPG) is filled in gas cylinders in the compressed gas form.
Question 5.
Liquid generally have lower density as compared to solids, but ice floats on water. Find out, why.
Answer
Ice and water both are the same substance but ice has greater volume than that of the same amount of water.
As density is inversely proportional to the volume, ice is less denser than water.
Objects having density less than water float on the surface of water.
Question 6.
What is dry ice?
Answer
Solid
C
O
2
is called dry ice, because solid
C
O
2
gets converted directly into gaseous state without coming into liquid state on decreasing pressure to one atmosphere.
Question 7.
Explain why temperature remains constant during interconversion of states of matter?
Answer
Heat supplied to a substance is getting used during changing its state to overcome the force of attraction between the particles. The excess heat is absorbed by the particles in the form of latent heat.
Question 8.
Give reason to explain why it takes longer time to dry wet clothes in humid weather?
Answser
Rate of evaporation depends on humidity present in air. Humid air already has large amount of water vapours, so rate of evaporation is slow.
Question 9.
Why should we wear cotton clothes during summer?
Answer
We perspire more during summer. Cotton is a good absorber of water. It absorbs sweat and exposes it for easy evaporation. As a result body feels cool and comfortable. So, we should wear cotton clothes during summer.
Question 10.
Why does a desert cooler cool better on a hot dry day?
Answer
The humidity that is the amount of water vapours in air is less on a hot dry day. Lesser the humidity more is the rate of evaporation. Since the rate of evaporation is more on a hot dry day, a desert cooler cools better.
Explanation:
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