Concepts

Class 9
Chapter 1 Class 9 - Matter In Our Surroundings

 SOLIDS LIQUIDS GASES Particles are closely bound Particles are close to each other, but not as much as solids Particles are much far apart compared to solids and liquids Fixed shape No fixed shape, they take the shape of the container No fixed shape, fill the entire space they are enclosed in Fixed volume Fixed volume No fixed volume Do not flow like liquids and gases Flow easily as particles slide over each other Flow easily as the particles can move easily from one place to another Maintain their form and occupy only as much space as their size Do not fill the container completely as they have greater density than gases Fill the container fully due to their low density Cannot be compressed easily Cannot be compressed easily as the particles are relatively close to each other Can be compressed easily as they have low density

Let's look at Properties of each one by one

## Properties of Solids

• Solids have fixed shape and fixed volume
Size of solids do not change and it occupies fixed space

• Particles of Solid are closely bound
There is higher force of attraction between particles

• Solids do not take shape of container like liquids
Example - If ice is put in a container, it does not take shape of container

• Solids do not flow like liquids
Liquids flow from one place to another. However, solids have fixed shape and do not flow or move

• Particles of solid cannot be compressed easily

Let's do some questions, shall we?

### Question 1

Rubber band changes its shape. Then why is it called solid?

• Rubber band changes its shape only on stretching (when a force is applied on it)
• When force is removed, it retains its original shape
• Hence, we can say that rubber band has fixed shape
• Also, it satisfies all other properties of solids (it has fixed volume, it does not flow like liquids and do not take shape of container)

### Question 2

Salt and Sugar do not appear to have fixed shape. Why is it still a solid?

• Sugar/Salt are made up of tiny crystals
• Shape of these crystals are fixed
• Hence these are called solids
• Sugar/Salt appear to take shape of container where they are kept but this is because of their small size, they do not actually change shape

## Properties of Liquids

• Liquids have fixed volume, but not fixed shape
They take shape of container
they are kept in

• Particles of Liquids are closely to each other (but not as close as solids)

• Liquid does not fill container completely like gases
(This is because particles of liquids have higher density than gases and are close to each other)

• Liquids are able to flow easily as particles are able to slide over each other

## Properties of Gases

• Gases have no fixed volume, no fixed shape

• Particles of Liquids are far from each other

• Gases fill the container completely like gases
(This is because particles of liquids have higher density than gases and are close to each other)

• Gases flow easily as particles are free to flow easily from one place to another

• Particles of gas can be compressed easily because of their low density

Introducing your new favourite teacher - Teachoo Black, at only ₹83 per month