Our Environment - Class 3 Notes & Olympiad Questions

Our Environment

a) An environment is a place where living and non-living things exist together.
b) Living things in our environment are things that can grow, move, and reproduce, like plants, animals, and humans.
c) Non-living things in our environment are things that are not alive, such as air, water, soil, and sunlight.
d) Living things are also called "biotic elements," while non-living things are called "abiotic elements."
e) When living and non-living things come together in an environment, we call it an ecosystem.
f) In an ecosystem, living organisms rely on non-living things for their survival. For example, plants and animals need water and air to live and grow.
g) Ecosystems can be found in many different places, such as forests, seas, lakes, and more. They can come in different sizes too, from small ones to large ones.

Air

a) Air is the invisible stuff that surrounds us all the time. It is like a big blanket of gas that covers the Earth. It's everywhere, even though we can't see it.
b) Air is made up of different gases. Some of these gases are very important for us to breathe and stay alive.
c) One of these gases is called oxygen. We need oxygen to breathe and to survive. When we breathe in, our bodies use the oxygen from the air to help us stay alive and give us energy.
d) Air also has other gases like carbon dioxide and nitrogen. These gases don't help us breathe, but they play important roles in nature. For example, plants use carbon dioxide from the air to make their own food through a process called photosynthesis.
e) Air can also have things like dust particles, smoke, and water vapour in it. These things can sometimes make the air look hazy or cloudy.
f) The air around us forms a protective layer around the Earth called the atmosphere. The atmosphere helps to shield us from the Sun's harmful rays, like ultraviolet rays, which can be dangerous to our skin.

Air Pollution

a) Air pollution occurs when harmful substances like dust and smoke from factories and cars contaminate the air we breathe.
b) This polluted air can be harmful to our health as well as to plants and animals. Breathing in this polluted air can cause symptoms like coughing, sneezing, and difficulty in breathing.
c) To reduce air pollution, we can use cars less, plant trees, recycle, avoid burning things, and raise awareness about the issue.

Water

a) Water is really important for our planet and for us to live. About three-fourths of the Earth's surface is covered with water. We can find water in many different places like oceans, lakes, and rivers.
b) Water is crucial for our lives. We use it for lots of things like washing our clothes, cleaning, drinking, cooking, taking baths, and even growing crops to have food. Without water, life would be very difficult.
c) Water can exist in three different forms: solid, liquid, and gas. When it's very cold, the water turns into ice, which is the solid form. When we see water flowing in rivers or coming out of our faucets, it's in its liquid form. And when water heats up, it can turn into a gas called water vapour, which we can't see.
d) Rain is one of the main ways we get water. When clouds in the sky get heavy with water vapour, they release it as rain. This rain provides us with the water we need.

Water Cycle

The water cycle is a way of describing how water moves between the sky and the Earth. It has a few important steps:

a) The sun shines on the water in rivers, lakes, seas, and oceans, and it gets really warm. This makes the water turn into water vapour. This step is called evaporation.
b) The water vapour goes up into the sky. As it goes higher, it gets cooler, and it turns back into tiny drops of water. This is called condensation. When many of these tiny drops join together, they make clouds.
c) When the clouds get full of water, they can't hold it all anymore. The water drops fall from the clouds back to the Earth. Sometimes, it falls as rain, which is what we usually see. But in colder places, it can fall as snow, sleet, or even hail.
d) The rainwater or melted snow, sleet, or hail flows into rivers, lakes, and oceans. It goes back into the water bodies, and then the whole process starts again.

This is how the water cycle keeps going in nature.

Properties of Water

a) Water is a clear liquid that you can see through. It doesn't have any colour or taste. When water is clean and pure, it doesn't have any smell either.
b) Water takes up space. It has weight and a certain amount of volume. So if you pour water into a container, it will fill up that container.
c) Water can take the shape of whatever container it is put in. It doesn't have its own specific shape. It can flow easily, like when you pour it out of a glass or a bottle.
d) Water can change its form easily. When it gets really cold, water can turn into a solid called ice. When it's heated up, water can become a gas called water vapour, which you can't see but is there in the air around us. So water can change between solid, liquid, and gas forms depending on how hot or cold it is.

Water Solution

a) When we mix one substance into another substance and it completely dissolves, we get something called a solution.
b) The substance that we mix in is called the solute.
c) The substance that the solute dissolves into is called the solvent.
d) When we have a mixture of the solute and solvent, we call it a solution.
e) For example, if we put sugar in water and stir it, the sugar is the solute, and the water is the solvent. When they mix together, we get sweet water, and that's the solution.

Floating and Sinking

a) When objects are heavier than water, they sink in them. For example, items like rocks, bricks, metal keys, and iron screws will sink when we put them in water.
b) Objects that are lighter than water will float on their surface. For instance, materials like wood, foam, plastic toys, and rubber balls will float when placed in water.

Rainwater Harvesting

a) Nowadays, the shortage of water has become a major issue. We need to find ways to save water, and one simple method is called rainwater harvesting.
b) Rainwater harvesting means collecting and saving rainwater in special structures. Instead of letting the rainwater go down the drains and get wasted, we collect it for later use.
c) So, rainwater harvesting is like saving rainwater in containers so that we can use it later when we need it. It helps us not waste water and make sure we have enough for the future.

Water Pollution

a) Water pollution happens when harmful substances contaminate water sources like rivers, lakes, and oceans. These substances can include chemicals, toxins, sewage, and waste from industries and human activities.
b) Water pollution is harmful to aquatic life, plants, and even humans who rely on clean water for drinking and daily activities.
c) To stop water pollution, we need to treat waste properly, not let chemicals get into the water, and use water responsibly.