Question

summarize ch-14 in 15 points (class 6)

Answer 1

Answer:

Three States of Water

Water can exist in all the three states—solid, liquid and gas.

Liquid state: The water that we use in everyday life is a liquid. It is called liquid state of water.

Gaseous state: We have learnt that on heating, water evaporates to form its vapor. Water vapor is its gaseous state.

Solid state: Water turns into ice on cooling. Ice is the solid form of water.

These three states of water are interconvertible to each other, that is, we can change it from one state to another.

Evaporation

The process of changing water to its vapor form is known as evaporation.

Evaporation takes place from open surfaces of water all the time—day and night.

Transpiration

Transpiration: It is the loss of water from the leaves of plants in the form of vapor.

Condensation

Condensation: The process of conversion of vapor into liquid form of water is called condensation.

The process of condensation is opposite to evaporation.

Cloud formation: The climate close to the earth’s surface is warm. It gets cooled as one goes up in atmosphere. Water vapor being lighter, rises up in the atmosphere. At the upper layer of atmosphere, where the temperature is lower, the vapor gets condensed into tiny water droplets and forms clouds.

Precipitation

Precipitation: Clouds carry small droplets of water in them. It may so happen that many droplets of water come together to form larger sized drops of water. Such drops of water may become so heavy that they begin to fall. Falling of water drops is called precipitation.

Rain: If the water during precipitation remains liquid till it reaches the surface of the earth, we have rains.

Hail/Snow: Sometimes precipitation may be in the form of hail or snow. Water in a hail or snow is in its frozen or solid form.

Dew: Many times, especially during winter nights, the air near the surface becomes quite cool. As a result, the water vapor present in it condenses to form water droplets. These water droplets appear as dew.

Water Back to Ocean

The water that falls on the land as rain and snow sooner or later goes back to oceans. This may happen in many ways.

Uses of Water

It is needed for drinking, bathing, washing, cleaning of vessels, toilets, flushing, etc.

Our body contains about 70 per cent of water. Therefore, water is essential for our life.

• Water helps animals and plants to cool.
• Water is essential for the germination of seeds.
• Water is required for irrigation of the crops.
• Water is used to generate electricity.
• Water wheel is used to run flour mills.
• Water is used in many industries, like paper, rayon, petroleum refining, fertilizers, dyes, drugs and other chemical industries.
• Water is used in car radiators to keep the engine cool.
• In cold countries, people use water to warm their houses.
• Water is used to keep the things cool.

Sources of Water

• Rivers and springs
• Oceans and seas
• Snow
• Groundwater
• Water table
• Lakes and ponds
• Rain

Natural Calamities

Drought: If it does not rain for a year or more at a place, the soil will lose its water by evaporation and becomes dry.

Flood: In case of continuous rains, the water level of rivers, lakes and ponds will rise. The soil surface will get laden with water resulting into flood.

Water Conservation

• It is very important that water should be used carefully. We should take care that water should not get wasted.
• It is not necessary that the water used in the garden is fit for drinking.  We should use water for gardening that has already been used in the kitchen for washing vegetables and fruits, etc.
• Always be careful that the water tank in your house doesn’t overflow when it is being filled.
• Don’t use a hose pipe to wash your car or scooter. Use a bucket instead.
• If you leave the tap running while brushing your teeth, about 16 litres of water get used up. Fill a mug with water and use instead.

Rainwater Harvesting

Water harvesting is the activity of collection of rainwater directly by various means.

Harvested water can either be used immediately or it can be stored for later use.

Water Available For Use

About three-fourth of the Earth’s surface is covered with water. That is why it is also called the water planet.  Most of the water (about 97%) is in the seas and oceans as salt water. This water is too salty to be used for drinking and irrigation. Thus, only a tiny fraction (about 3%) of the Earth’s water is available to us as freshwater. Out of this, 2.997% is locked up in the mountains or glaciers or is buried so deep under that it costs too much to extract.

So, only about 0.003% of the fresh water is easily available to us in the form of groundwater, river, lake, stream, soil moisture, and water vapour.