Everything around us is made of matter. All matter can exist in three forms: Solid, Liquid or Gas. Matter can change states through heating or cooling i.e, solid can be changed into liquid or liquid can be changed into solid. These three states are:
A block of wood and ice is solid. A solid has a certain size and shape. A solid does not change size or shape. Other examples of solids are the computer, the desk, and the metals.
You can change the shape of The molecules of solid are very tightly packed.
Milk and water are liquids. These are liquid forms of matter. It has a size or volume. Volume means it takes up space. But milk or water does not have a definite shape. They take the shape of its container. Like if you pour milk in a cup or a glass, it takes that shape.
Liquids can flow, be poured, and spilled.You can change the shape of liquids either by heating or decreasing the temperature. For example, if you heat water ,water-vapors are formed. Similarly of you keep it in a refrigerator; it becomes ice, which is a solid.
The molecules of liquid are very loosely packed.
Try to run very fast for a minute. Do you notice how hard you are breathing? What you are breathing is oxygen? We all need oxygen to live. That's why we can only hold our breath for a certain amount of time.
But you can't see oxygen. It is invisible. It is a gas. A gas is matter that has no shape or size of its own. Gases do not have any color.
Gases are all around us. We can feel gases when the wind blows. The wind is moving air. Air is a mixture of many gases.