Define: diffusion - Chemistry


Define: diffusion



The phenomenon of intermixing of particles of one kind with another kind is called diffusion.

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Chapter 3: Matter - Exercise 2


Selina Class 6 Selina Concise Chemistry
Chapter 3 Matter
Exercise 2 | Q 9.2


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.

A diver is able to cut through water in a swimming pool. Which property of matter does this observation show?

What are the characteristics of particles of matter?

When sodium chloride is added to a definite volume of water and stirred well, a solution is formed, but there is no increase in the level of water. Why?

What is volume ?

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.

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

Give reason for the following.

Pure substances have fixed melting or boiling points.

Fill in the blank:

Liquids have no definite ............

For the following statement, say whether it describes a solid, a liquid or a gas.
 Particles move about very quickly.

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

  1. solid
  2. liquid
  3. gas
  4. water

A solid is a state of matter that has

  1. no definite shape.
  2. large intermolecuiar space.
  3. high intermolecuiar force of attraction.
  4. no definite volume.


  1. cannot be compressed easily,
  2. occupy the entire space of the container.
  3. have definite shapes.
  4. cannot flow.

What is volume ?

Fill in the blank

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

Write whether the following statement are true or false.

The intermolecular force of attraction is the weakest in gases.

Write whether the following statement are true or false.

Intermolecular force of attraction is greater in gases than in liquids.

When sugar is dissolved in water, there is no increase in the volume. Which characteristic of matter is illustrated by this observation?

Which single term is used to describe the mixing of copper sulphate and water kept in a beaker, on its own?

What is the general name of :

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

Explain the following :

When an incense stick is lighted in the corner of a room, its fragrance spreads quickly in the entire room.

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 one of the following statements is not true?

  1. the molecules in a solid vibrate about a fixed position
  2. the molecules in a liquid are arranged in a regular pattern
  3. the molecules in a gas exert negligibly small forces on each other, except during collisions
  4. the molecules of a gas occupy all the space available

 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 ____

A measuring cylinder is filled with water to a particular mark. A piece of solid is immersed inside the measuring cylinder. State why the level of water in the measuring cylinder will rise up. If the solid is removed, what will be the new level of the water in the measuring cylinder? Give a reason for your answer.

A glass beaker is half-filled with water and an empty glass tumbler is inverted & lowered inside the glass beaker. State your observations on tilting the tumbler below the level of the water in the glass beaker. Give a reason for your answer.

Differentiate the general properties of solids, liquids and gases in the form of a table — with reference to space.

State in which of the three states of matter:

The movement of the particles is neither about their own positions nor in any random direction.

Give a reason why –

Solids have a definite volume & a definite shape.

Give a reason why –

Liquids have a definite volume but no definite shape.

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.


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