A Journey through States of Water

Class 06 Science

Ice and water are the two forms of the same substance. These forms are also called states. These different states of water show many differences in their behaviour. Water flows but ice does not. Water splashes but ice does not.

Water gets converted into gaseous state called water vapour. The water vapour is another state of water. The process of conversion of water into its vapour state is called evaporation. The process of evaporation takes place continuously, even at room temperature.

When the water vapour present in the air comes in contact with a cold surface, it forms water droplets. The process of conversion of water vapour into its liquid state is called condensation.

Different States of Water

Water is a substance that can be observed in three different states in our daily life. In the solid state, it exists as ice. On heating, the ice melts and gets converted into its liquid state. On further heating, water gets converted into its gaseous state.

Ice (solid state) retains its shape irrespective of the container in which it is placed while water takes the shape of the container. Ice does not flow or spread.

Water (liquid state) flows and changes its shape. Water does not have a fixed shape. It takes up the shape of the container in which it is kept, but the volume of water remains constant. Water also has the property to spread while keeping the volume constant.

Water vapour (gaseous state) exhibits a property of spreading out in the entire available space. Gases do not possess a fixed shape. Water vapour exists even at room temperature, though it is invisible to us. It is present in the air around us. The water that evaporates during processes like drying of clothes or mopping of floors contribute to the water vapour in the air around us.

How can we change the States of Water?

If we have to change ice into water, and water into water vapour, we have to supply heat to it.

If we want to change water into ice, it can be done by placing water in a cold environment, such as a freezer. Water freezes and is converted into ice.

The process of conversion of a solid into liquid state is called melting. The process of conversion of liquid into solid state is called freezing.

Cooling Effect

Earthern pot (matka): Water seeps through the surface of the earthen pot and evaporates, which imparts a cooling effect on the water.

Sprinkling water on the floor or the roof during summer cools it.

How do Clouds give Rain?

Condensation plays a significant role in the process of bringing evaporated water back to the Earth’s surface. When air moves higher above the Earth’s surface, it becomes cooler and cooler. At certain heights, the air gets so cool that the water vapour in it turns into droplets which are generally formed around dust particles. These small droplets float in the air and form clouds. Many droplets join together to form bigger drops of water. Some drops get so heavy that they start falling. These falling water drops is called rain.

Under special conditions, it might also fall as hail or snow.

Water Cycle

The water from the ocean and the Earth’s surface evaporates into the atmosphere as vapour and returns as rain, hail or snow, ultimately flowing back to the oceans. This circulation of water is known as the water cycle.

Use of Water

Only a small portion of water available on the Earth is fit for use by plants, animals and humans. Most of the water is in the oceans and it cannot be used directly. We use water for drinking and also for many other activities.

The number of people using water is increasing with a rise in population. The increasing demand for water causes its shortage in many parts of the world. Hence, it is very important to use water wisely and avoid wasting it.