Give Reason Of We Can Walk Through Air. - Chemistry

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Give reason of We can walk through air.



The molecules of air are far apart i.e. large gaps and we can walk through air easily.

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Chapter 1: Matter and Its Composition - Additional questions


Selina Concise Chemistry Class 7 ICSE
Chapter 1 Matter and Its Composition
Additional questions | Q 26.4


Give reasons for the following observation:

The smell of hot sizzling food reaches you several metres away, but to get the smell from cold food you have to go close.

Fill in the blank:

The change of water vapour into water is called ......................

Why can a piece of chalk be broken easily into smaller pieces while a coal piece cannot be broken easily?

Classify the following into solids, liquids and gases.
Oxygen, milk, common salt, wax, stone, water vapour, carbon-dioxide, sugar, mercury, coal, blood, butter, copper, coconut oil, kerosene.

Define interconversion of states of matter.

Define the following terms.


Fill in the blank:

Any matter which has a definite.................... but no definite shape is called a...............

Fill in the blank:

Water boils at ............

Fill in the blank:

Liquids have a definite ............

 Match the columns.

(1) iron and gold (a) molecules are very far apart
(2) melting (b) pure substance
(3) intermolecular space (c) non - metals
(4) compound (d) the space between the molecules 
(5) gases (e) change from solid to liquid 
  (f) metals


Name the phenomenon which cause the following change:

Conversion of ice into water.

If an object is taken to the moon from the earth what will be its mass ?

Define the following term Intermolecular force .

Give reason of A gas fills up the space available to it.

Give reason of The odour of scent spreads in a room.

Give reason  of When a teaspoon of sugar is added to half a glass of water and stirred, the water level in the glass does not rise.

Give reason

A red ink drop added to small amount of water in a glass turns water red in some time.

Fill in the blank

The molecules are at a greater distance in ______ compared to liquids.

The state of matter which has no definite shape or volume is called

There are large intermolecular gaps in

A piece of chalk can be broken into small particles by hammering but a piece of iron cannot be taken into small particles by hammering. Which characteristic of the particles of matter is illustrated by these observations?

What is the general name of :

  1. rigid form of matter ?
  2. fluid forms of matter ?

State two characteristics of matter demonstrated by diffusion.

Explain why, we can easily move our hand in air but to do the same through a plank of wood, we need a karate expert.

Which one of the following statement is correct in respect of fluids?

In which of the following conditions, the distance between the molecules of hydrogen gas would increase?

  1. increasing pressure on hydrogen contained in a closed container
  2. some hydrogen gas leaking out of the container
  3. increasing the volume of the container of hydrogen gas
  4. adding more hydrogen gas to the container without increasing the volume of the container

Which of the following statement is incorrect?

When a beam of sunlight enters a room through a window, we can see tiny particles X suspended in a gas (or rather a mixture of gases) Y which are moving rapidly in a very haphazard manner.

  1. What could particles X be ?
  2. Name the gas (or mixture of gases) Y.
  3. What is the phenomenon exhibited by particles X known as ?
  4. What is causing the movement of particles X ?
  5. What conclusion does the existence of this phenomenon give us about the nature of matter ?

Define: diffusion

 Define: interconversion of states of matter.

What are the two conditions for the interconversion of states of matter?

Give reasons for the following:

Solids have a definite shape and are highly rigid while gases have to definite shape and are least rigid.

Give reasons for the following:

Sugar can be distinguished from talcum powder using water.

Give reasons for the following:

Water on freezing turns into ice.

Give reasons for the following:

A bottle of perfume on opening evolves an odour which can be sensed over a long distance.

Complete the statement given below by selecting the correct word.

The space between atoms in gases is maximum while in ____ is minimum,

Fill in the blank with the correct word Given below.

The space between atoms’ [molecules] of solids is ____

State in which of the three states of matter:

The force of attraction between the particles is very weak.

200 ml of water is poured into a bowl of 400 ml capacity. The volume of water will be ______.

Among the following ______ is not a mixture.

Water obtained from tube wells is usually ______ water.

Air is not compressible.

Match the following.

Property Example
Breaks easily (Brittle) Metal pan
Bends readily Rubber band
Can be stretched easily Cotton wool
Gets compressed easily Mud pot
Gets heated readily Plastic wire

Mr. Raghu returns home on a hot summer day and wants to have buttermilk. Mrs. Raghu has the only curd. What can she do to get buttermilk? Explain

In a glass containing some water, tamarind juice and sugar are added and stirred well. Is this a mixture? Can you tell why? Will this solution be sweet or sour or both sweet and sour?

Which one of the following element name is not derived from planet?

The Cow and Birds are nonliving things.

Mention any two characteristics of the particles of matter.

You are provided with a mixture of naphthalene and ammonium chloride by your teacher. Suggest an activity to separate them with well labelled diagram.


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