# Solids, Liquids and Gases

### Concept: Solids, Liquids and Gases

This concept mainly deals with the properties of solid, liquid and gas.

After reading the concept, students will be able to:

• Understand what is solid.
• Know the arrangement of molecules in solid, liquid and gas.
• Know the properties of liquids.
• Recall the characteristics of gas.
• Understand that air is a mixture of gases.

Each concept is explained to class 4 students using descriptions, illustrations, and concept maps. After you go through a concept, assess your learning by solving the two printable worksheets given at the end of the page.

Download the worksheets and check your answers with the worksheet solutions for the concept of the Properties of Solid, Liquid and Gas provided in PDF format.

Matter is anything around us that occupies space and has mass. It can be divided into three categories—Solids, liquids, and gases. These are called the three states of matter, and they constitute tiny particles called molecules.

Let us now have a closer look at the different states of matter.

1. Solids:

• Solids have a definite size, shape, mass, and volume.
• A solid never changes its shape when it is moved.
• The molecules of solids remain closely packed.
• The molecules of solids do not freely move around in all directions; rather, they remain fixed.
• The propagation of sound is the fastest in solids.
• The force of attraction between the molecules of solid materials is the maximum.

Example: Stones, pebbles, wood, chalk, buildings, tables, chairs, pencils, books, diamonds, etc.

2. Liquids:

• Liquids have no definite shape and size.
• Liquids have a fixed volume.
• They take the shape of the containers they are poured into.
• The molecules of a liquid are loosely attached and move freely.
• The molecules of the liquids are loosely packed, which is why they can take the shape of the containers they are poured into.
• The force of attraction between the molecules of a liquid is moderate.
• The volume of a liquid can be measured.
• The shape and size of a liquid cannot be measured.
• Liquids can move from a higher level to a lower level.

Examples of Liquids: Oil, water, milk, blood, gasoline, coffee, tea, honey, maple syrup, etc.

3. Gas:

• Gases are present all around us and fill almost every vacuum space.
• Balls, balloons, and bubbles all are filled with gas.
• Air is also a gas.
• The molecules of gases have a lot of space between them and can move freely.
• Gas molecules move a little faster than liquid molecules.
• Gases have no definite size, shape, and volume.
• There are essentially no attractive forces between the gas molecules in most cases.
• It means that gas has nothing to hold a specific shape or volume.

Example: Helium is a very light gas that is mostly used to fill gas balloons; there are gases in the atmosphere like carbon dioxide, oxygen, nitrogen, argon, etc. Car fumes are nothing but a mixture of different gases; factory fumes are also gases.

### New Words:

Vacuum: It means a space where no matter is present.

Volume: The amount of space occupied by an object.

### Did You Know?

• Gas molecules can be compressed easily. When gas molecules are close enough, they get transformed into a liquid state. This is how LPG or Liquefied Petroleum Gas is manufactured.