Organisms and Environment: Grade 5 Science

Step outside on a cold winter morning. The grass is white with frost. Your breath makes little clouds. Then the Sun climbs over the hill. The frost melts. Birds begin to sing. A lizard creeps out of a crack in the wall and sits in the sunshine.

Everything wakes up with the Sun. In this unit you will find out why. You will see how plants and animals use the Sun’s heat and light. Then you will look at the energy we use every day. Where does it come from? How can we use it without harming the world around us?

Living things and their environment

Look at the picture. Talk about it with your friends.

Figure 3.1 A grassland beside a pond. The living things are named in green, red and brown. The non-living things are named in blue.

The world around us has two kinds of things.

Living things: plants and animals (and mushrooms too). They grow, take in food, breathe and have young ones.
Non-living things: soil, water, air, heat and light. They don’t grow or eat.

All the living and non-living things of a place, together, make its environment.

Living things can’t live alone. A rabbit needs grass to eat. The grass needs soil, water, air and sunlight. Plants and animals get their heat and light from the environment too. So living and non-living things are linked. Each one depends on the others.

Which of these is a non-living part of the environment?

Pick an answer to see why.

Heat and light for living beings

Look at the pictures. What is the Sun doing in each one?

Figure 3.2 Six jobs the Sun does for us. Its light and heat dry paddy and clothes, help a leaf make food, help a baby’s body make vitamin D, warm the land and lift water into the sky, and make electricity in a solar panel.

The Sun is our main source of light and heat. Here is what its light and heat do.

For plants

Plants make their food in sunlight.
Plants need warmth to grow, to flower, to make fruit and to ripen their seeds.
Warmth helps leaves give out the extra water a plant has taken in.

For animals

Animals need heat to keep their bodies warm.
They need warmth to have young ones.

For people

The Sun dries our wet clothes and our grain.
It can cook food, in a solar cooker.
Sunlight on our skin helps the body make vitamin D. This keeps our bones strong.
Solar panels make electricity from sunlight.

For the whole Earth

Sunlight takes away darkness and makes the day bright.
The Sun’s heat warms the land, so living things can live on it.
The Sun’s heat turns water from seas, rivers and ponds into vapor. This is called evaporation. The vapor forms clouds, and rain falls again. This is the water cycle.

What is our main source of heat and light?

Pick an answer to see why.

Plants need sunlight

What happens to a plant that gets no sunlight? Try it and see.

Project

3.1: does a plant need sunlight?

Aim: to see how sunlight changes a growing plant.

You need: two pots of the same size, soil, manure, water, a jug, and seeds of one kind of pulse (beans or gram).

Mix fine manure into the soil. Fill both pots with the same amount.
Sow the same number of seeds in each pot.
Keep both pots in a place with no sunlight. Water them equally every day.
Look every day. Have the seeds sprouted?
When they have sprouted, put one pot outside in the sun. Put the other in a dark room where sunlight never reaches. Keep watering both.
Every week, look at the color of the leaves. Measure the height of the plants with a ruler.
Fill in a table like this one. Talk about it in class, and write what you found.

Changes after sprouting		Pot in the sun	Pot in the dark room
Color of the plants	First week
	Second week
	Third week
Height of the plants (cm)	First week
	Second week
	Third week

What I found: the plants in sunlight were ______ in color and ______. The plants without sunlight were ______ in color and ______.

What you should see

The seeds sprout (germinate) in both pots, even in the dark. A bean or gram seed has its own food stored inside, so it doesn’t need light to sprout. It needs water, warmth and air.
After that, the two pots look very different:

In the sun: the plants are green. Their stems are thick and strong, and their leaves open wide.
In the dark: the plants are pale yellow. Their stems are thin and weak. Their leaves stay small and folded.

The plants in the dark often grow taller at first. They are stretching to find light. But they are weak and floppy. When the food in the seed runs out, they droop and die.
What I found: the plants in sunlight were green in color and healthy and strong. The plants without sunlight were yellow in color and thin and weak.

Two pots of beans sprouted at the same time. One went into the sun. One went into a dark room. Move the days on and watch them grow.

Days since the pots were moved: 0

Both pots have just sprouted in the dark. The sprouts are small and pale. Move the days on.

In the sun, the sprouts turn green in a day or two. In the dark, they stay pale yellow and shoot up fast.

The plants in the dark are taller, but thin and yellow, with tiny folded leaves. The plants in the sun are green and strong, with wide leaves.

The food stored in the seeds is used up. The plants in the dark can’t make more, so they flop over. The plants in the sun keep making food and growing.

Why does a plant turn yellow in the dark? Green leaves have a green coloring in them called chlorophyll. Chlorophyll catches sunlight. The plant uses that light to make its food from water and a gas in the air called carbon dioxide. The water comes up from the roots. The carbon dioxide comes in through the leaves.

The food the leaves make helps the whole plant grow. Without sunlight, the plant can’t make food. It also stops making chlorophyll, so its leaves turn yellow.

Figure 3.3 A green plant making its food. Sunlight falls on the leaves. Carbon dioxide from the air goes into a leaf. Water comes up from the roots. The leaf gives out oxygen. You will learn more about this in Grade 6.

What is the green coloring in leaves called?

Pick an answer to see why.

Animals need heat and light

A dark speckled hen sitting on a nest of straw — **Figure 3.4** A hen sitting on her eggs in a nest of straw. Her warm body keeps the eggs warm. After about 21 days, the chicks hatch. Photo: Cleur Monie, CC BY-SA 4.0

Animals need heat to:

grow and develop their bodies;
keep their bodies warm;
hatch their young ones from eggs.

Animals need light to:

see things around them;
find food and a safe place to stay;
escape from their enemies.

On a cold day, a dog lies in the sun. A cat curls up in a warm corner. People sit around a fire. An eagle needs daylight to spot a fish in the water.

Why does a hen sit on her eggs?

Pick an answer to see why.

A lizard’s body is as warm as the air around it. Your body always stays at 37 °C. Slide the air temperature down to winter and see what the lizard does.

Air temperature: 20 °C

Air: 20 °C
Lizard (cold-blooded): 20 °C
You (warm-blooded): 37 °C

The lizard’s body is as cold as the air: too cold to move. It hides in a crack and rests through the winter (hibernation).

The lizard is cold and slow. It looks for a sunny spot to bask in and warm up.

The lizard is warm and quick: it can run, climb and catch insects.

Too hot! The lizard hides in a shady crack to cool down.

You stay at 37 °C: you shiver and put on warm clothes.

You stay at 37 °C, comfortably.

You stay at 37 °C: you sweat, and the sweat drying cools you.

Different places, different plants

Project

3.2: plants where you live

Which trees, fruits and vegetables are found where you live? Look around, or ask your elders. Fill in a table like this one. Then talk in class about how heat and light change what grows.

The name of the place I live: ______

No.	Trees	Fruits (winter)	Fruits (summer)	Vegetables (winter)	Vegetables (summer)
1.
2.
3.

What you should see

Your table depends on where you live. In the hills, it might look like this:

No.	Trees	Fruits (winter)	Fruits (summer)	Vegetables (winter)	Vegetables (summer)
1.	pine	orange	peach	cauliflower	cucumber
2.	chestnut (katus)	lemon	pear	radish	pumpkin
3.	alder (utis)	guava	plum	spinach	beans

Some plants grow well in the cold of winter. Others need the long, hot days of summer.

Why do different places have different plants? It depends on three things: how much rain falls, how many hours of sunshine there are, and how warm or cold it is.

Nepal has three kinds of land: the Himalaya (mountains), the hills and the Terai (plains). As you go north, the land gets higher. The higher the land, the colder the air. The usual weather of a place, year after year, is called its climate. So each region has its own climate, and its own plants.

Terai: hot. Sal, sissoo, mango and bamboo grow here.
Hills: milder. Pine, walnut, chestnut and rhododendron grow here, and fir higher up.
Himalaya: cold. Spruce, fir and juniper (dhupi) grow here. Their leaves are thin and shaped like needles.
High Himalaya: too cold for trees. Snow covers the ground in winter. Grasslands appear only in summer, when the snow melts.

Figure 3.5 Nepal from south to north. The land rises from the hot Terai to the cold Himalaya, and the plants change on the way. Above the trees, grass grows only in summer.

A forest of rhododendron trees covered in red flowers on a hillside — **Figure 3.6** A rhododendron forest at Ghorepani, in the hills. Rhododendron (*laligurans*) is Nepal’s national flower. It blooms red, pink and white in spring. Photo: Greg Willis from Denver, CO, usa, CC BY-SA 2.0

Dark pointed fir trees in front of high snowy mountains — **Figure 3.7** Fir trees below the snowy Manaslu range. Their leaves are thin needles. Snow slides off the pointed trees, and needles lose little water in cold, dry winds. Photo: Mohan K. Duwal, CC BY-SA 4.0

Which plant has thin, needle-shaped leaves?

Pick an answer to see why.

Tomatoes in winter: the plastic tunnel

Activity

3.1: read the conversation and talk

It is the first day of school after the winter holidays. Four friends from Grade 5, Shravan, Devaki, Phurwa and Kamala, are walking along a hill path.

Shravan: The holidays went so fast!

Devaki: And it’s so cold these days!

Phurwa: A cold wind has been blowing all morning.

Kamala: I got up early today. Our whole yard was white with frost!

Shravan: Look over there. What’s under that plastic?

Devaki: Tomatoes! Lots of them, red and ripe!

Phurwa: But it’s too cold up here in the hills. Plants don’t grow well now.

Kamala: So a plastic tunnel lets you grow vegetables out of season!

Shravan: All the tomato plants at our house have died. How did these grow so well?

Kamala: The Sun’s heat gets into the tunnel easily, but it can’t get out. So it is warmer inside than outside, and the plants grow well.

Talk about it:

a.Why did the plants outside the tunnel die?
b.Why did the tomatoes in the tunnel grow so well?
c.How can vegetables be grown out of season?

Answer

a.It was too cold outside. Frost and cold winds damaged the tomato plants, and they died.
b.Sunlight passes through the clear plastic and warms the soil and the air inside. The plastic keeps that warm air from blowing away. It also keeps off frost and cold wind. So the tomatoes stayed warm, and grew and ripened.
c.In a plastic tunnel or a greenhouse. Farmers cover a frame of bamboo or metal with clear plastic and plant inside. The plants get sunlight and stay warm, even in winter.

Tall tomato plants with red and orange tomatoes inside a tunnel of clear plastic, with a woman picking them — **Figure 3.8** Picking tomatoes inside a plastic tunnel. Farmers in Nepal’s hills use tunnels like this to grow tomatoes, chillies and cucumbers out of season. Photo: U.S. Department of Agriculture, CC BY 2.0

A winter’s day in the hills. Try each cover, by day and at night. Which cover helps the tomato plant most?

Cover:

Time:

No cover: the plant gets full sunlight, but the winter air is cool. It grows slowly.

No cover: at night the air drops to 1 °C and frost forms on the leaves. Night after night, the frost kills the plant.

Clear plastic: sunlight passes through and warms the soil and air inside to about 28 °C. The plant makes food and grows well.

Clear plastic: it cools at night, but stays warmer than outside, and no frost settles on the leaves. The tomatoes ripen.

Black plastic: the plastic soaks up the sunlight and the inside is warm, but almost no light reaches the plant. It can’t make food, and turns yellow.

Black plastic: as warm as the clear tunnel at night. But by day the plant is in the dark, so it turns yellow and weak.

Long days and short days

In summer, the days are long. In winter, they are short. So in summer, plants get sunlight for many hours. Summer is also warm. Plants grow fast, and many flowers bloom.

In winter, the days are short and cold. Plants get less heat and light. So most plants grow slowly in winter.

Figure 3.9 How long the Sun is up in Kathmandu, in the middle of each month. In June it is up for almost 14 hours. In December, only about 10½ hours.

Not all flowers open in the daytime. Parijat (night jasmine), jasmine and queen of the night (brahmakamal, ब्रह्मकमल) open in the evening or at night. So do the small flowers of raat ki rani (रातकी रानी).

Small white flowers with orange centers among green leaves — **Figure 3.10** Parijat (night jasmine) in Panchkhal, Kavre. Its flowers open in the evening. By morning, many have fallen to the ground. Photo: Krish Dulal, CC BY-SA 3.0

One large white flower with many petals and yellow stamens, open at night — **Figure 3.11** Queen of the night (*brahmakamal*, ब्रह्मकमल), a cactus with flat, leaf-like stems. Its big white flower opens after dark, smells sweet, and fades by morning. Each flower opens for one night only. Photo: Alfieri José Larocca, CC BY-SA 3.0

A bunch of small white star-shaped flowers on long thin tubes, against a dark background — **Figure 3.12** Raat ki rani (रातकी रानी), a small bush grown in many gardens. In English it is sometimes also called queen of the night, but it is a different plant. Its little white flowers open in the evening. At night their sweet smell carries a long way. Photo: SKsiddhartthan, CC BY-SA 4.0

Some plants like the cold. Pine, juniper, chestnut and walnut grow well in cold places. Apple trees in Jumla and Mustang need a cold winter to flower well in spring.

Why do most plants grow slowly in winter?

Pick an answer to see why.

A box in the sun

Project

A box in the sun

Aim: to compare the temperature inside and outside a clear box in the sun.

You need: a small clear plastic or glass box, and a thermometer.

Measure the temperature outside the box. Then put the thermometer inside and measure again. Write both down.
Put the box in the sun for about half an hour.
Measure the temperature inside and outside the box again.
Fill in a table like this one, and write what you found.

No.	The box	Temperature outside the box	Temperature inside the box
1.	Before it is put in the sun
2.	After it has been in the sun

What I found: the temperature inside the box is ______ than outside.
Talk about what you found in class.

Use a room thermometer, not a fever thermometer. A fever thermometer reads only from about 35 to 42 °C.

What you should see

Before the box goes into the sun, the inside and outside read the same. After half an hour in the sun, the inside is warmer, often by 10 °C or more.
What I found: the temperature inside the box is higher than outside. Sunlight gets in through the clear sides. The warm air inside can’t get out. A plastic tunnel works the same way.

In short

Heat and light for living beings

Environment: all the living things (plants, animals) and non-living things (soil, water, air, heat, light) of a place. They depend on one another.
The Sun is our main source of heat and light.
Plants need sunlight to make food. Their green chlorophyll catches the light. They make food from water and carbon dioxide. Without light, a plant turns yellow, thin and weak. Plants need warmth to grow, flower and make fruit.
Animals need heat to grow, keep warm and hatch eggs. They need light to see, find food and escape enemies. Frogs, snakes and lizards rest through winter.
Different places have different plants, because of rain, sunshine and cold. Himalayan trees like spruce, fir and juniper have needle-shaped leaves.
A plastic tunnel lets sunlight in and keeps warmth in, so vegetables grow even in winter.
Summer days are long and warm, so plants grow fast. Winter days are short and cold, so plants grow slowly. Some flowers, like parijat, open at night.

Exercise (Heat and light for living beings)

1. Choose the best answer

a. Which of these is the main source of heat?

Pick an answer to see why.

b. What is the main reason plants don’t grow well in winter?

Pick an answer to see why.

c. What is the main job of a tunnel for growing vegetables?

Pick an answer to see why.

d. To make food, a plant needs water from its roots. What else does it need?

Pick an answer to see why.

2. Is it correct (✓) or wrong (✗)?

a. A hen needs light to hatch chicks from her eggs.

Pick an answer to see why.

b. Plants grow faster in places that get sunlight for longer.

Pick an answer to see why.

c. Plants found in the Himalaya have needle-shaped leaves.

Pick an answer to see why.

d. Heat, light, soil and air are non-living parts of the environment.

Pick an answer to see why.

e. A tunnel helps the plants inside by not letting sunlight in through the plastic.

Pick an answer to see why.

3. Fill in the blanks

chlorophyll, environment, favorable, cold, yellow, suitable, green

Energy is obtained from the ______.

Answer

Energy is obtained from the environment.

______ weather is needed for farming.

Answer

Suitable weather is needed for farming. (“Favorable” is also right.)

In bad weather, animals move from their homes to ______ places.

Answer

In bad weather, animals move from their homes to favorable places. (“Suitable” is also right.)

Plants turn ______ when they get no sunlight.

Answer

Plants turn yellow when they get no sunlight.

______ is found only in green plants.

Answer

Chlorophyll is found only in green plants. (“Cold” and “green” are not needed.)

4. Answer these questions

List any three sources of heat and three sources of light.

Answer

Heat: the Sun, a fire, an electric heater (also a gas stove, a candle).

Light: the Sun, an electric bulb, a torch (also a candle, a kerosene lamp).

Why don’t plants grow well in places with no sunlight?

Answer

Plants need sunlight to make their food. Without it, they can’t make food, so they can’t grow.
Without sunlight, they stop making green chlorophyll. Their leaves turn yellow.
They grow thin and weak, and in the end they die.
Places with no sunlight are also cooler, and plants need warmth to grow and flower.

Why are plastic tunnels used to grow vegetables in winter?

Answer

Winter is too cold for many vegetables. Frost and cold winds can kill them. In a plastic tunnel, sunlight passes through the clear plastic and warms the soil and the air inside. The warm air can’t blow away, and frost can’t settle on the plants. So it stays warmer inside than outside. The plants also still get light. That is why vegetables like tomatoes grow well in a tunnel even in winter.

For what jobs do living things need heat?

Answer

Plants need heat to grow, to flower, to make fruit, to ripen their seeds, and to give out extra water from their leaves.
Animals need heat to grow, to keep their bodies warm, to have young ones, and to hatch their eggs.

Sources of energy in the environment

Inside a small mill: grain pours from a wooden hopper onto a round millstone, with white flour around it — **Figure 3.13** Inside a water mill (*ghatta*) in Gadsera, Doti. Under the floor, a stream spins a wooden wheel. The wheel turns this millstone, which grinds the grain that trickles in from the hopper above. Photo: Janak Bhatta, CC BY 4.0

Rows of cow dung, shaped into rolls, drying in stacks on the grass — **Figure 3.14** Dung cakes (*guitha*) drying in Nepal. Cow dung is mixed with straw, shaped and dried in the sun. Then it is burnt for cooking. Photo: Ravijung, CC BY-SA 4.0

Activity

3.3: the energy you use

What energy do you use every day? Where does it come from? What do you use it for? Copy the table and fill it in. The first row is done for you.

No.	Source of energy	Where it comes from	Kind of energy	Uses
1.	firewood	forest	heat	cooking food, keeping warm
2.
3.
4.
5.

What you should see

For example:

No.	Source of energy	Where it comes from	Kind of energy	Uses
1.	firewood	forest	heat	cooking food, keeping warm
2.	electricity	hydropower station	light, heat, movement	lights, fans, TV, rice cooker, charging phones
3.	cooking gas (LPG)	made from oil and gas from deep under the ground, brought from other countries	heat	cooking food
4.	sunlight	the Sun	heat and light	drying clothes and grain, solar water heater
5.	petrol and diesel	oil from deep under the ground	movement	running buses, motorbikes and trucks
6.	biogas	cow dung	heat	cooking food

Where does energy come from?

We need energy to do every job: to cook, to give light, and to move things from one place to another.

Energy from the Sun is called solar energy. It reaches the Earth as heat and light. All living things need it.

Plants use sunlight to make food.
Animals eat plants, or eat other animals that ate plants.
Wood, firewood and charcoal come from plants.
Cow dung is made into dung cakes (guitha) and biogas.

So the energy in firewood, dung and our food all came from the Sun first.

The Sun also gives us hydroelectricity. Follow the picture.

Figure 3.15 From the Sun to a bulb. (1) The Sun’s heat turns water into vapor. (2) The vapor cools and makes clouds. (3) Rain falls on the hills. (4) Rivers carry the water down. (5) A dam holds the water, and the falling water spins a turbine. This makes electricity. (6) Wires carry it to our homes.

Electricity is used in homes, schools, offices and factories. But making it takes a lot of work and money. So we should never waste energy.

Where did the energy in firewood first come from?

Pick an answer to see why.

Harke Dai and the firewood

A story from science

Harke Dai goes to the forest

Early one morning, Pawan and Geeta from Grade 5 meet Harke Dai on the village path.
Pawan: Where are you going so early, Harke Dai?
Harke Dai: To the forest. I have no grass and firewood left, so I’m going to cut some.
Pawan: But cutting firewood in the forest is not allowed, is it?
Harke Dai: That’s why I’m going early, before anyone sees me.
Geeta: Oh no, Harke Dai! If everyone cuts too much firewood, the forest will be destroyed.
Pawan: And the animals that live there will lose their homes. Some may die out.
Harke Dai: Hmm. What else happens if there are no trees?
Geeta: The soil gets washed away easily.
Pawan: And on bare hills, more landslides happen in the rainy season.
Harke Dai: But how will I cook without firewood? I can’t buy kerosene or gas.
Pawan: We don’t mean never use firewood. Collect dry and fallen wood, with permission.
Geeta: And when a tree is cut, plant new ones.
Pawan: You can also cook and boil water with biogas or electricity.
Harke Dai: Electricity? How do you cook with that?
Pawan: With an electric heater or an induction stove. They cook easily. They make no dust or smoke, so the air stays clean.
Harke Dai: I still think kerosene is easier.
Geeta: It’s not, Harke Dai. Smoke from coal, kerosene, diesel and petrol makes the air dirty. It harms our health.
Pawan: And these fuels will run out. New ones take hundreds of millions of years to form.
Harke Dai: Oho! Now I understand. You are young, but so wise. Thank you!

Here is what Pawan and Geeta taught Harke Dai. Using energy carefully, without wasting it, is called energy conservation.

Cutting too many trees destroys the forest. Animals lose their homes and may die out.
Without trees, rain washes the soil away, and bare hills slide down as landslides.
Use firewood wisely: take only dry and fallen wood, with permission. Plant new trees.
Cook with cleaner energy: biogas, or electricity with an induction stove. They give no smoke.
Coal, kerosene, diesel and petrol make smoke that dirties the air and harms our health. They are called fossil fuels. They formed under the ground over hundreds of millions of years. Once used up, they are gone.

Activity

3.4: talk and write

Talk with friends in your neighborhood. Why is energy important? What happens when we waste energy? Then write a short essay on “Using energy wisely”.

What you should see

Here is one short essay.
Using energy wisely
We need energy for everything. We cook with it, light our homes with it and travel with it. But we often waste it. Lights and fans stay on in empty rooms. Too many trees are cut for firewood.
Wasting energy harms us. Forests disappear, and animals lose their homes. Bare hills slide in the rain. Smoke from firewood, kerosene and diesel dirties the air and makes us ill. Coal and petrol will one day run out.
We can do better. Switch off lights and fans when you leave a room. Cook with a pressure cooker and an improved stove. Use biogas, solar energy and electricity from our rivers. Plant a tree. Small steps by everyone can save a lot of energy.

A white three-wheeled electric tempo on a street in Kathmandu — **Figure 3.16** A Safa tempo in Kathmandu. These three-wheelers have run on batteries since the 1990s. *Safa* means clean: they give out no smoke. Photo: Krish Dulal, CC BY-SA 3.0

Using energy without harming the environment

Activity

3.5: things that help

Look at these things: an improved stove, a pressure cooker, hydroelectricity, an electric vehicle, a solar panel, a biogas plant and a gas stove. How does each one reduce harm to the environment? Copy and fill in the table. The first row is done for you. Share it in class.

Thing	How it reduces harm to the environment
Improved stove	Less firewood is used. Food cooks faster. Smoke goes out through a pipe, so the kitchen and house are free of smoke.
Pressure cooker
Solar panel
Hydroelectricity
Electric vehicle
Biogas
Gas stove

What you should see

Thing	How it reduces harm to the environment
Improved stove	Less firewood is used. Food cooks faster. Smoke goes out through a pipe, so the kitchen and house are free of smoke.
Pressure cooker	Food cooks much faster, so less fuel is burnt.
Solar panel	Makes electricity from sunlight. It burns nothing and makes no smoke, and sunlight never runs out.
Hydroelectricity	Makes electricity from flowing water. No fuel is burnt, so there is no smoke. Rain keeps refilling the rivers.
Electric vehicle	Gives out no smoke on the road. In Nepal it runs on electricity from rivers.
Biogas	Made from dung, so no trees are cut. Its gas burns cleanly, with no smoke. What is left makes good manure.
Gas stove	No trees are cut, and there is far less smoke than with firewood. (But cooking gas is a fossil fuel. It will run out.)

Figure 3.17 Two kitchens. On an open fire, smoke fills the room, and much of the heat escapes around the pot. In an improved stove, the fire is closed in and the heat goes to the pot. A chimney takes the smoke out of the house.

People building a biogas plant in a deep round pit; a big dome of smooth soil fills the pit, with a stick standing on top — **Figure 3.18** Building a biogas plant in Nepal. In a deep pit, soil is shaped into a dome. Cement laid over it makes the plant’s round roof. Then the whole plant is buried, and only its inlet, outlet and gas pipe show. Dung and water go in. Inside the closed pit, tiny living things break down the dung and make **biogas**. A pipe takes the gas to the kitchen stove. Photo: SuSanA Secretariat, CC BY 2.0

Energy that runs out, energy that comes back

Some sources of energy will finish if we keep using them. Coal, kerosene, petrol, diesel and cooking gas formed under the ground over hundreds of millions of years. Once they are burnt, they are gone. These are non-renewable sources of energy.

Other sources come back again and again. The Sun shines every day. Rain keeps refilling the rivers, so hydroelectricity never runs out. Wind keeps blowing. Forests grow again if we plant new trees. Cows make fresh dung every day for biogas. These are renewable sources of energy.

So, in our homes, schools, offices and factories, we should:

use less of what runs out, like kerosene, petrol, diesel and other mineral oil;
use more of what comes back, like biogas, wind power, hydropower and solar power.

Tap a card. Then tap the box it belongs in.

Tap a card, then tap the bin it belongs in.

0 of 12 sorted

Which of these is a renewable source of energy?

Pick an answer to see why.

Exercise (Sources of energy)

1. Choose the best answer

a. Which of these is a renewable source of energy?

Pick an answer to see why.

b. Which of these sources of energy makes the air most polluted?

Pick an answer to see why.

c. Which of these sources of energy doesn’t pollute the air?

Pick an answer to see why.

d. Which of these is a good way to stop wasting energy?

Pick an answer to see why.

2. Is it correct (✓) or wrong (✗)?

a. Electric vehicles cause pollution.

Pick an answer to see why.

b. Using too much energy, and wasting it, harms the environment.

Pick an answer to see why.

c. There is plenty of coal in nature.

Pick an answer to see why.

d. Leaving the lights on in a room with nobody in it wastes energy.

Pick an answer to see why.

3. Fill in the blanks

excessive, electricity, Sun, pollution, less, coal

______ is a source of energy that will finish if we keep using it.

Answer

Coal is a source of energy that will finish if we keep using it.

______ use of energy makes the natural sources of energy run out.

Answer

Excessive use of energy makes the natural sources of energy run out.

Using solar energy doesn’t cause ______ in the environment.

Answer

Using solar energy doesn’t cause pollution in the environment.

The ______ is the main source of energy.

Answer

The Sun is the main source of energy. (“Electricity” and “less” are not needed.)

4. Answer these questions

Make a list of things we use as sources of energy in daily life.

Answer

Firewood, charcoal, dung cakes, biogas, cooking gas (LPG), kerosene, petrol, diesel, coal, electricity, batteries, sunlight (solar panels, solar water heaters, drying clothes) and flowing water (a water mill).

Write any two ways to save energy that you have used or seen at home or in your community.

Answer

Any two, for example:

switching off lights, fans and TV when nobody is using them;
cooking with a pressure cooker, and on an improved stove;
using LED bulbs, which give the same light with much less electricity;
drying clothes in the sun instead of with a heater;
walking or cycling for short trips;
using a solar water heater.

“Biogas is better than firewood as a source of heat.” Give any two reasons.

Answer

Any two:

Biogas burns with no smoke, so the kitchen stays clean and our eyes and lungs stay healthy. Firewood fills the kitchen with smoke.
Biogas is made from dung, so no trees are cut. Using firewood destroys forests.
Biogas is renewable: cows make fresh dung every day.
The waste left after making biogas is good manure for the fields.

Which is better to use, a diesel vehicle or an electric vehicle? Give a reason.

Answer

An electric vehicle is better.

It burns no fuel, so it gives out no smoke. A diesel vehicle’s smoke dirties the air and harms our health.
Diesel is a fossil fuel that will run out, and Nepal has to buy it from other countries. Nepal makes its own electricity from its rivers, and rivers don’t run out.

Choosing the right source of energy helps keep the environment clean. Explain with an example.

Answer

Some sources make smoke and use up forests. Others don’t. If we choose the clean ones, the air stays clean and forests are saved.
Example: a family cooks on an open wood fire. Smoke fills the kitchen, and trees are cut for firewood. Then they build a biogas plant and cook with biogas. Now there is no smoke, no trees are cut, and the waste from the plant becomes manure. By choosing the right source of energy, they keep their home and the environment clean.

Write the ways to conserve energy.

Answer

Switch off lights, fans, TV and computers when they are not in use.
Use LED bulbs instead of old bulbs.
Cook with a pressure cooker, on an improved stove. Cover the pot with a lid.
Use the Sun’s energy: dry clothes and grain in the sun; use a solar water heater.
Use renewable sources such as biogas, solar power and hydroelectricity, instead of kerosene and diesel.
Walk, cycle or take a bus instead of a car or motorbike.
Take only dry, fallen firewood, and plant new trees.

Worksheet to print (PDF, 3 pages) Answer key for teachers

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