This lesson will help you to: -
- understand the properties of water.
- determine various sources of water.
- know about various uses of water.
- learn the importance of water conservation.
- learn and incorporate different ways of saving water.
- understand the concept of water cycle.
Real Life Examples
- When someone is sweating, the sweat evaporates and cools down the person.
- Mechanical cooling apparatus like refrigerating and air- conditioners use evaporating gas to extract heat from what we like to cool down
- The phenomenon of condensation can be seem when water appears on your windshield after you park your car outside on a particularly humid night.
- A rat is the only animal that can stay the longest without water.
- It takes 1900 liter of water to make 1 kg of rice.
- A person can survive without food for more than 30 days but less than a week without water.
- The longest river in the world is the Nile River. It reaches 6650 kilometers in length.
- Set in the desert of Dubai, the Tiger woods golf course uses 4 million gallons of water every day to maintain its lush appearance.
QUICK CONCEPT REVIEW
- Water is the most common substance found on Earth. About 3/4 of Earth is covered with water.
- The body content of plants, animals and humans comprises mostly of water.
STATES OF WATER
Water exists in three states- Solid (Ice), Liquid (Water) and Gas (Vapour/Steam). Earth is the only planet that supports all these states.
As seen in the picture, we can observe that when ice is heated it gets converted to water which on further heating turns into vapour. When vapour is cooled it becomes water again. And on freezing the water we see the formation of ice.
PROPERTIES OF WATER
- Shapeless i.e. it takes the shape of the container in which it is poured
- Colourless-pure water is colourless
- Tasteless-pure water has no taste. It can be made sweet or salty by adding sugar/salt to it.
- Odorless-pure water has no smell.
SOURCES OF WATER
Rainwater, oceans, rivers, lakes, streams, ponds and springs are natural sources of water. Dams, wells, tube wells, hand pumps, canals etc., are manmade sources of water.
Some of the rain water seeps through the soil and becomes underground water. Spring is stored underground water.
India is surrounded on three sides by water. Arabian Sea in the west. Bay of Bengal in the east and Indian Ocean in the south.
Some important rivers of India are The Ganga,
The Brahmaputra, The Indus, The Krishna, The Kaveri and The Godavari.
- Letting the tap run when you brush your teeth wastes up to 4 gallons of water every time.
- The kangaroo rat, a type of rat, never drinks water!
- Earthworms come out from soil after rains because the earthworms live underground and the rain fills up their homes.
- Pond skater is an insect that can walk on water! The surface skin of the water dents a little around their feet, but it does not give way.
- Early man was dependent on water for their survival. They Lived near the water and did fishing until they took the vegetarian root and started searching for food in the form of fruits and vegetables in the jungles.
USES OF WATER
Water is a very useful Resource
- It is used for produce electricity.
- It is used for transportation.
- It is used for washing and cleaning.
- It is used for drinking and cooking.
WATER AND HUMAN BEINGS
- Our body fluids like blood, urine, tears and sweat are all made up of water.
- It quenches our thirst.
WATER AND PLANTS
- Plants also require water for their survival and growth.
- They make their own food with the help of water, sunlight, carbon-dioxide and green pigment called chlorophyll present in their leaves. This process is called photosynthesis.
WATER AND ANIMALS
- Just like plants, animals also need water for their survival.
- Plants and animals that live in water are called as the aquatic plants and aquatic animals respectively.
- Animals that can live on both land and water are called as amphibians. Ex. Frogs, toads and turtles.
- Nature recycles and reuses its resources. Water also gets recycled through water cycle.
- Water cycle is the continuous movement of water from the Earth's surface into the air and back to the Earth again. During the whole process, water keeps changing its form continuously.
- Two important processes of water cycle are Evaporation and Condensation. Due to the sun's heat, water changes into vapour and rises up in the air (evaporation). On cooling down, it changes into drops of water and comes down as rain from the clouds (condensation).
- Precipitation-Rainwater is very important for every living being. Rainfall brings the most needed water to the earth.
Children love to play in rain but do you know the Peackock, also loves rain and enjoys dancing in rain.
Rain water is used for various purposes. It refills the water bodies on earth like rivers, ponds, lakes etc. which get dried up in the absence of rain. In many parts of India, we are still dependent on rains for our crops. If the rains fail, the crops also fail.
The rainfall is not equally distributed throughout the earth. Some places receive more rainfall while other places get very little or no rainfall. Insufficient rains causes water scarcity and drought.
It is better to save this rain water and use it when we have water shortage. One such method is Rainwater Harvesting.
Every Drop is Precious!
- Water is a very precious resource.
- Water should not be wasted. It should be saved, reused and conserved.
- Water conservation means to reduce the use of water.
Ways to save water
- Stop the running water while bathing, washing, brushing teeth, shaving etc.
- Use of bucket instead of shower while bathing.
- Collect water which is used for rinsing fruits and vegetables and then use it for watering the plants.
This is a method of conserving water. Rainwater is saved because it is clean and a precious resource and can be used for many useful purposes.
Misconcept: Condensation is when air turns into a liquid.
Concept: Condensation is water vapour in the air that cools enough to become a liquid.
Misconcept: Steam is hot air.
Concept: Steam is water vapour.
Misconcept: Water only gets evaporated from the ocean or lakes
Concept: Water can evaporate from plants, animals, puddles, and the ground in addition to bodies of water.
Misconcept: Condensation on the outside of a container is water that seeped (or sweated) through the walls of the container.
Concept: Condensation of water vapour happens when the water vapour in air comes in contact with a cool surface.