Kids Learning Science

4th Standard Science Term-III

Air We Breathe

    Introduction    

Our earth consists of land, water and air.  All these components are very much important for the survival of all living creatures.  Air is present all around us.  It is very important to cause rain and for the growth of crops.  It is needed for the respiration of plants and animals.

   Importance of Air in Our Daily Life   

1. Oxygen present in air is needed for respiration.

2. We can hear the sound only when there is air around.

3. Air helps in the dispersal of seeds for plant reproduction.

4. Monsoon and rain occurs due to the wind action.

5. Air regulates the atmospheric temperature.

   Air is a Mixture   

The air we breathe consists of a mixture of gases.  It contains dust, water vapour and smoke.  Air also contains gases like oxygen and nitrogen.  Air shows the properties of all the gases present in it.

For example, air supports combustion because oxygen is present in it.  While cooking using firewood, fanning air helps in burning of firewood.

   Composition and components of air   

The composition of air is not constant.  It varies from place to place and over time.  Air is not a single element; it is made up of different substances.

Nitrogen

The amount of nitrogen present in air is about 78%.

It is used to fill up food package to extend their shelf life.

Liquid nitrogen is used to store living cells.

Plants need nitrogen for their growth.  We can see root nodules containing nitrogen in some plants.

Nowadays people use nitrogen gas to fill the tyres of their vehicles.  Some compounds of nitrogen are used as explosives also.

Oxygen

It is one of the main components of air.  The amount of oxygen present in air is about 21%.  All the creatures cannot live without oxygen.  The presence of oxygen can be tested with simple experiments.

Uses of oxygen

1. All living things use oxygen for breathing.

2. Oxygen is essential for burning.

3. Oxygen cylinders are used in hospitals to enable the patients to breathe when they cannot breathe normally.

4. Oxygen is used in gas welding.

Carbon dioxide

The amount of carbon dioxide present in air is only 0.03%.  Though it is less in percentage its uses are more and essential.  It can be tested with lime water.  The lime water changes from colourless to milky.

Uses of carbon dioxide :

1. Carbon dioxide helps plants in photosynthesis.

2. It is used in fire extinguishers.

3. It is used in refrigerators as dry ice for cooling purposes.

4. It is used to make plastics and polymers.

Air has other gases like hydrogen, helium, argon etc.  in small proportion.  Air also contains water vapour which varies according to the environment.  When we breathe, we take oxygen from air and release carbon dioxide and water vapour to air.

   Air pollution   

The atmosphere of earth is disturbed by human activities.  This leads to environmental problems like air contamination and global warming.  The air carries soot, smoke and other particles from car exhaust and power plants.  These are the major contributors to air pollution.

Adverse effects of Air pollution

Global warming

This changes the climatic conditions of different regions of the world.  It also causes disturbances in agriculture and food production.  Melting of snow caps and increase in sea levels are the consequences of global warming.

Formation of smog

When dust particles and smoke combine with fog in the presence of sunlight, smog is formed.  It reduces the visibility.  It also causes many respiratory disorders and allergies.

 

Formation of acid rain

Sulphur dioxide and

nitrogen oxides react with water in the atmosphere producing sulphuric acid and nitric acid.  These acids come down along with the rain.  This is called acid rain.

Acid rain

• causes respiratory and skin disorders 
• damages the leaves and affects the productivity of plants.
• enters the ground and river waters causing harm to the aquatic life.
• erodes marble and damages monuments like Taj Mahal.

Aerosol formation

When liquid or solid particles are dispersed in air, it is called aerosol.  Aerosols are deposited on the leaves affecting photosynthesis.

Depletion of Ozone

The hydrocarbons such as the Chlorofluorocarbons (CFCs) destroy the ozone layer.  Ozone holes allow the UV rays to reach the earth's surface.  UV radiation harms wildlife, damages plants and causes skin cancer in humans.

Effects of Air pollution of human beings

Air pollution has bad impact on human health.  When the pollutants increase in air, they cause irritation in the eyes, nose and throat.  Air pollution can also produce wheezing, coughing and breathing problems in humans.

Some of the major effects of air pollution on human beings are :

1. Respiratory diseases. E.g. Tuberculosis

2. Cardiovascular damage.

3. Fatigue, headaches and anxiety.

4. Nervous system damage.

Steps to check air pollution

Air pollution can be reduced by the following steps.

1. Alternative source of energy (E.g. Solar energy) should be used.

2. Air filters should be used to prevent harmful gases mixing with air.

3. Smoke emission test and certification of motor vehicles must be enforced.

4. More trees should be planted to absorb carbon dioxide.

Kids Learning Science

    

4th Standard Science Term-III

Life of Animals

Introduction 

    Have you ever wondered why a dog drools on seeing food?  Why cuckoo sings only during summer?  Why baby birds open their mouths when the mother returns to the nest? 

    Each animal has some unique behaviour.  Animal behaviour includes the activities of an animal and its interaction with other organisms.  E.g. Blinking, eating, walking and flying.

Group Behaviour in Animals

    Animals gain a lot of benefits by living together with other members of the same species.  The is called group behaviour.  Animals like tiger, bear etc live in solitary (alone).  Some animals live in small groups (E.g. Pride of a few lions) and some live as larger herd (E.g. Herd of thousands of wilde beest).

    Group behaviour is also called social behaviour.  Members of the group work together to find food, defend themselves and look after the young ones.  The main purpose of group behaviour is to help animals survive in nature.  E.g. All the fish in a school move together, following their leader in the front.  Staying in a group helps the small fish appear big.

Group behaviour in Bees

    When insects live together, they often follow a hierarchy.  E.g. Bees have one queen bee in every hive.  There are a few male bees called drones.  There are hundreds of female bees, which are the worker bees.

Nesting Behaviour in Birds

    Birds are very different from each other.  They live in different places, eat different foods and have different life styles.  Some birds permanently live in groups while others come together only during the breeding season.  Birds also live in groups.

  

  Not all the bird species build nests.   Some of them lay their eggs on the ground or in gap between rocks.  Most of the birds build their own nests carefully like engineers.  They build nests for their young ones.  Some weave leaves, some use twigs, some build with thorns then pad it with soft materials.

Group behaviour in Elephants

    Elephant group is called Herd or Parade.  For each group there is a female head, which leads the group towards the availability of food, water and safety.  The leader fights for their group.   All animals in a group obey the command of their leader.  Older animals teach manners and life skills to young ones.  Like elephants deer, bisons and monkeys also live in groups.

Kids Learning Science

4th Standard Science Term-III 

Green Environment

Introduction

Nature provides us with a lot of useful things.  Factories use these natural resources to make things that we buy in shops.  When we are finished using these things, they become waste.  Waste is any object or material that has been used but is not wanted anymore.  It is not useful to us because it is broken, worn out or cannot be used again.  Waste can be solid, liquid or gas and can come from many places such as houses, schools, markets, hospitals, shops, etc.  Generally waste pollutes our environment.

Waste Management

Sristhika : Madam, I see a lot of waste things in our surrounding.  Is there any way we can reduce wasting things?

Teacher : Yes.  There are many ways to reduce waste.  Reducing the waste is the first and most important step in waste management.

Vimal : What is waste management, Madam?

Teacher : It is the step we take to handle our waste and to make sure our environment does not get dirty and polluted.  Waste management deals with both biodegradable and non-biodegradable waste.

Janani : Can you please explain the steps in waste management Madam?

Teacher : Yes, sure.  There are four steps in waste management.  They are 

1. Separation of Waste 

2. Waste collection and transportation 

3. Waste recycling and composting 

4. Waste disposal.

1. Separation of Waste : This is a very important step in waste management.  It means to sort or divide the waste in different waste bins.  Each bin should have different type of wastes.  It is good to separate waste in three different bins.  Green for biodegradable waste, Blue for recyclable waste and Red for non-recyclable waste.  Non-biodegradable waste can be classified as recyclable and non-recyclable.

2. Waste collection and transportation : Once we separate our waste in our homes and schools, it is important to keep it ready to be picked up by our panchayat, municipality or corporation.  Picking up the waste is called Waste collection.  Moving the waste from one place to another is called Waste Transportation.

3. Waste recycling and composting : Biodegradable waste is taken to a place where it can be converted into compost.  Compost is food for plants and helps to make our soil healthy.  Non-biodegradable (recyclable) waste is taken to recycling factory for making new products.

4. Waste disposal : The waste that cannot be recycled (non-recyclable waste) needs to be sent for final disposal.  This waste is sent to an open dump or landfill.

Rahul : How can we manage waste at home?

Teacher : There are many things we and our family can do to manage waste at home.  3Rs help to manage waste.

Gomathi : What are the 3Rs, Madam?

Teacher : The 3Rs stand for REDUCE, REUSE, RECYCLE.  We must first reduce, then reuse and finally recycle.  They are in this order to help us remember what to do first.

THE 3Rs

Reduce is to make and use less materials.  This is to make, buy and use things that create less waste.  It is the best thing to do first.  How can make less waste? Some examples are given below.

1. You can buy an ink pen.  When the ink is used up, you can refill and use it.

2. While shopping with your parents, you can carry a cloth bag.  In this way you can avoid buying plastic carry bags.

3. You can use your own vessels for purchasing snacks items.

4. You can reduce waste by buying things in bulk instead of in small quantities.

Reuse is using a thing repeatedly for the same or for another purpose.  By reusing, we throw away less waste and do not dispose of it in a dump.  Reuse saves money, energy and time.  Here are some examples of how you can reuse materials at home.

1. You can reuse old clothes to clean your home.

2. You can reuse jam and pickle jars to store things.

3. You can donate old clothes which can be used.

4. You can reuse waste and make something new.  E.g. You can reuse a plastic battle as a pen stand or a bird feeder.

Recycle is to take materials from things you throw away and make new products by using them.  Recycling takes energy and time but saves the amount of 'new' resources (for example water, minerals, wood) we need to make things.

Here are some examples of how certain materials are recycled.

1. Old newspapers, note books and magazines are kept separate and sold to a scrap dealer.  They will be made into new paper.

2. PET bottles are recycled into plastic threads and then used to make sports T-shirts.

3. Old glass bottles and broken glass pieces are melted to make new glass.

4. Broken metal items are melted and made into new metal products like toys.

Conservation of Environment

Rahul : What is meant by conservation of environment, Madam?

Teacher : Conservation of environment means to protect all things found in nature.  It means that we have to use to use our Earth's natural resources (like water, soil, minerals, wildlife and forests) carefully.

Vimal : How can I conserve the environment?

Teacher : Everyone can help to conserve the environment by following good waste management habits.

What is the first 'R' in the 3Rs?

Kanimozhi : Reduce.

Teacher : Correct! We should first try to reduce the waste we make.  Thus, we can easily conserve our environment.

Waste Separation

Household waste should be separated into biodegradable, recyclable and non-recyclable categories.  Biodegradable waste such as left-over-food and vegetable waste can be broken down naturally to create compost.  Recyclable waste such as paper, glass and metal can be made into new useful products.  Non-recyclable waste should be kept separate and will be sent to an open dump or landfill.  This should be reduced as much as possible.

Sristhika : I have heard the news that plastic is harmful to our environment. Is it true Mam?

Teacher : Plastic itself is not bad but we are using too  much of it.  Over use of plastic causes pollution.  Plastics that are used only one time causes pollution.   It is good to avoid or reduce one-time use plastics.  The best way to start is to ask yourself this question.  Is this plastic item going to be used one time or many times?  If you can use it only once, then try to avoid buying such plastic items.

Plastics in Tamil Nadu

Tamil Nadu is leading the way in India by banning some one-time use plastic items.  List of items banned in Tamil Nadu are given below.

Animals eat plastic bags by accident when they contain left over food.  A cow was found with over 50 kilos of plastic in its stomach.

Used Plastic plates will stay in the environment for over a 1,000 years.

Water pouches often get littered and are difficult to recycle.

Plastic straws are difficult to recycle and end up polluting the environment.

Chemicals from plastic sheets leak into food more when the food is hot.

Ekalaivan : What are the things that can be used instead of plastic, Madam?

Teacher : We can use things that are good for the environment.  These are called environmentally friendly or eco-friendly materials, and can be either biodegradable or reusable.

Environment friendly materials

Things that can be decomposed or broken down by microorganisms are biodegradable.  They can return back to the soil and become food for plants.  These biodegradable items are environment friendly or eco-friendly materials.

Let us learn more about them.

Leaf plates are a tradition in Tamil Nadu and very eco-friendly.  E.g. Banana leaf.  They are fully biodegradable and do not contain chemicals like thermocol plastic or coated paper plates.

Bamboo is used to make many things such as bags, dustbins and even toothbrushes.

Teacher : Some environment friendly materials are not biodegradable but they are very strong and can be used for many years.  By reusing, we can reduce waste and conserve the environment.

Rahul : Can you please give us some example?

Teacher : Yes, sure.

Stainless steel water bottle and snack box are some examples of eco-friendly materials.  Stainless steel does not leak chemicals into your food or water.  So it is safer than plastic.  These can be reused for a longer period of time.

Litter Free Environment

Litter in our environment is ugly to look at and causes pollution.  Wind and rain move litter into drains, rivers and lakes and often ends up polluting the ocean.  It is also dangerous to animals as they may eat.  Not littering is the best way to keep our community and environment clean.

National Green Corps (NGC)

It is a national programme initiated by the Government of India.  NGCs motto is :

"Where there is Green, there is Prosperity"

NGC schools students protect and promote the conservation of natural resources through participating in activities such as the conservation of forests and managing waste.

Always throw litter in a dustbin and when you travel always carry a bag with you to store your litter.

If you see litter, pick it up and throw it away in a dustbin as this show by example and encourages others to do the same.