AIR, WATER AND ROCKS - ESSENTIAL POINTS

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AIR

• Air is essential for all living things.
• We need air to breathe.
• Air cannot be seen but it can be felt when it moves.
• Fast moving air is called
• Slow moving air is called
• Air occupies space and has weight.
• Air is a mixture of different gases.
• Air contains gases like oxygen, carbon dioxide, nitrogen and dust particles. These gases are used by living things like plants and animals for survival and growth.
• Plants release oxygen in day time and carbon dioxide at night.
• Water gets converted to water vapour and mixes with air when air blows.
• When person coughs or sneezes, his germs mix with the air.
• Factories, trains and buses emit smoke that mix with the air.
• When anything is burnt the smoke mixes with air. Breathing impure air is harmful to our health.
• We should breathe in only clean and fresh air to avoid sickness.
• Fresh air comes into homes through doors and windows. So we should leave doors and windows open.
• Plants make air fresh and clean. So, plant more and more trees.

 Uses of wind

• Wind helps seeds to fly to far off places. These seeds grow into new plants.
• Wind helps boats sail on water.
• Wind dries our clothes.
• Wind moves windmill to produce energy.
• Wind vane or a wind sock tells us the direction in which the wind is blowing.

 Hazards of wind

• When wind blows very fast, it is called storm. Storm destroy houses, crops, trees and animals. Storms uproot trees and blow things away.

WATER

• Water is the most common natural substance. It covers about three fourth of the earth’s surface.
• All living things need water to live and grow.
• We should keep all the water bodies clean and we should not waste water.
• We need water to take bath, to remove our thirst and cooking.
• Plants need water to live and grow.
• Water has no color, odour or taste. 

• Water exists in all the three states depending on temperature.
  • Solid: Ice
  • Liquid: Rain, Clouds, Dew, Water.
  • Gaseous: Water vapours

• Water in form of gas

When water is heated, it starts boiling and changes into water vapours. These vapours are known as steam. Water vapours or steam are gaseous forms of water.

• Water in form of liquid

      The water we use in our homes is in form of liquid. It has no shape. It takes the shape of vessel in which it is kept.

• Water in form of solid

      Ice is solid form of water. Ice is hard and cold. They do not change shape when transferred from one vessel to another.

• Evaporation: Water on heating by heat/sun coverts into vapours. The process of change of liquid water into vapours is known as evaporation.

• Condensation: The process of change of vapour into liquid water is known as condensation. Condensation is a conversion of vapour or gas into a liquid.

• Water cycle in nature
  • When sun shines, it heats the water present in rivers, lakes, ponds and seas. This changes water into water vapours.
  • Water vapours rise up in air where they cool and turn into tiny drops of water.
  • These drops of water form clouds. In the clouds, drops join up to form large drops.
  • These drops become heavy and fall on earth as rain.
  • The rain water flows back into ponds, rivers, lakes and seas.
  • This cycle goes on and on in nature and is called water cycle.

ROCKS

• The major part of earth’s crust is made of rocks.
• The stones are small parts of rock.
• Clay and dust particles are made of rocks.
• Rocks are found on mountains and hills, they can be seen in valleys. They are also found under seas and rivers.
• Rocks are of many kinds and have many colors like black, white, red and grey.
• Rocks are usually hard.
• Granite is a very hard rock. Floor tiles are made from it.
• Marble is a hard rock. It is used for making buildings, statues and floors. The Taj Mahal in Agra is built of white marble.
• Sandstone is also a hard rock. It is not as hard as granite or marble. The Red Fort in Delhi is made of red sandstone.
• Rocks like coal, chalk and slate are soft. Steam engines move with coal, chalk is used to write on board.
• Chalk is made of gypsum.
• Roofs of houses are made of slate in snowfall regions.
• Electricity is produced in thermal power station by burning coal.
• All rocks are made up of minerals.
• Minerals are of different colors, shapes and sizes.

Uses of minerals

• Iron is used for making nails, tolls etc.
• Silica is used for making mirrors and glass.
• Tungsten is used in light bulbs.
• Quartz is used in watches.
• Graphite is used as lead of pencils.
• Talc is used for making talcum powder.
• Gemstones are very hard minerals. They are cut into various shaped and polished.
• In the original form, gemstones don’t look beautiful. When polished, they look very attractive.
• Diamond, garnet, sapphire and emerald are beautiful gemstones. They are used in making jewelry.
• Diamond is hardest substance and Talc is the softest mineral.