NCERT Solutions for Class 5 The World Around Us Chapter 7 Energy How Things Work (PDF) – 2027

Sample table — the first row is the book’s example. Any true observation from the picture or from your own kitchen is correct.

— at least three things under each heading:

Energy makes all of them happen. Whether a thing moves, shines, makes a sound, gets hot or gets cold, energy is behind it. In the book’s words:

What happens: the air rushes out of the mouth and the balloon shoots away in the opposite direction, zig-zagging and hissing, until the air is used up.

Why: the rushing air pushes the balloon forward. Moving air has energy.

What happens: the balloon, taped to the straw, zooms along the string from one end to the other. The air rushes out backwards and pushes the balloon forwards; the string keeps it on a straight path.

To make it faster: fill the balloon fully, pull the string tight and straight, and add no extra weight.
To make it slower: fill the balloon only half, let the string sag a little, or tape a coin to the balloon.

More air gives a bigger push; extra weight and rubbing hold the rocket back.

What happens: each plucked band vibrates — shakes to and fro very fast — and gives a twanging sound. The box and the hole make the sound louder. When you stop the band with a finger, the sound stops. This is sound energy.

Yes, they sound different. A thin band gives a high, sharp sound because it vibrates fast. A thick band gives a low, deep sound because it vibrates more slowly.

The water in the cup kept in the sunlight feels warm; the water in the shade stays cool. The Sun heated the water. This shows that sunlight gives us heat energy.

We are able to move because of energy — and we get that energy from the food we eat.

The reason is energy. Food gives us the energy we need. When we have not eaten, the body is short of energy and we feel tired. After we eat, the body has energy again and we feel active.

Animals also get their energy from food. Food is a source of energy for all living things.

They need fuel — petrol or diesel. Fuel is to a vehicle what food is to us.

In my house food is cooked on a gas stove. The stove is joined by a pipe to an LPG cylinder. The burning gas gives a blue flame that heats the pan, and the food cooks. On some days my grandmother cooks on a chulha using firewood.

We use LPG cooking gas from a cylinder. It lights at once, gives no smoke in the kitchen, and the flame can be made big or small.

Other homes may use firewood, cow-dung cakes, coal, kerosene, electricity or a solar cooker.

Burning a lot of wood or coal makes smoke and harmful gases. That dirties the air, harms our health, and forests are cut down to get the wood.

What happens: both wicks catch fire at first. The dry wick in Diya 1 soon burns out and its flame dies. Diya 2, with oil, keeps burning with a steady flame for a long time. (Do this only with an adult.)

Diya 2 — the one with oil — burns much longer. It burns longer because it has a fuel to keep the flame going. Diya 1 has no fuel, so its flame dies as soon as the dry cotton itself is burnt up.

The oil is the fuel. It burns and gives light and heat. The cotton wick is not the fuel — it only carries the oil up to the flame.

Many things at home run only on electricity — the fan, the tube light and bulbs, the television, the fridge, the mixer, the iron, the water pump, the mobile charger, the cooler, the washing machine and the doorbell.

Sample table — row 1 is the book’s example; your own devices may be different.

Yes. From this one table it is clear that electricity can do every job that energy does — it can move things, make sound, give light, make heat, and even make things cool.

My day would be much harder and slower. There would be no fan or light, no fridge to keep food fresh, no pump to fill the water tank, and no phone or TV. I would have to finish my homework before dark. Shops, hospitals and factories would find it hard to run their machines.

Yes — the Sun, the wind and flowing or falling water. Electricity made from these three does not fill the air with smoke, so it is called clean energy.

The cloth in the Sun dries first. It dries faster because sunlight gives heat, and heat turns the water in the cloth into water vapour more quickly.

You get a paper pinwheel that can spin on its pin. Remember three things: cut each diagonal only halfway to the centre, fold every other corner point into the centre, and keep the pin a little loose so the wheel turns freely.

The pinwheel spins round and round. When the wind is strong it whirs fast and its colours blur together. When the wind drops it slows and stops. If there is no wind, it starts spinning the moment you run with it.

The magnifying glass gathers the sunlight into one small, very bright spot on the paper. Move the glass up and down until the spot is smallest. Do it only with an adult. Never look at the Sun through the glass, and never point the spot at anyone.

The paper grows very hot at that one bright dot. It turns brown, then black, then starts to smoke, and if you hold the glass steady it catches fire and burns a small hole.

At step 4: the cup turns freely round the pencil, like a wheel on an axle. At step 5: rest the two ends of the pencil on the rim of a container, so the wheel hangs in the air and can spin.

Yes. The moment the falling water hits the spoons, the wheel starts to turn. Pour a thin stream and it turns slowly. Pour a thicker, faster stream and it spins quickly. Stop pouring and the wheel slows and stops.

Yes. Papads are spread on a sheet on the terrace and washed clothes are hung on a line. The Sun’s heat turns the water in them into water vapour, which goes into the air, so they dry. The Sun’s energy does this for free.

Yes. Some examples:

• The Sun: cooking in a solar cooker, heating water in a solar water heater, making electricity with solar panels, drying grain and chillies.
• The wind: flying kites, sailing boats, winnowing grain, windmills that make electricity.
• Flowing water: gharaats that grind grain, dams that make electricity, boats carried by the current.

Yes. Electric vehicles do not use petrol or diesel at all. They carry a large battery, and the battery is charged from an electric point, just as we charge a mobile phone.

Sample table — row 1 is the book’s example:

Make three sets of slips, with a different colour for each set:

Sample chains (source → type of energy → use). The first two are the book’s own examples. Each group says its chain in one sentence, like: “We are the heat of the Sun and we help to dry clothes.”

The whole day’s routine would change. Nothing that runs on a wire would work — no fan, no lights after dark, no fridge, no water pump, no TV, no charged phone.

Because solar and wind energy do not pollute the air, and they never run out. Coal makes a lot of smoke and harmful gases, and one day it will be finished.

1. A battery — a torch cell or a mobile phone battery stores energy and gives it out when we switch on.
2. Our body — it stores energy from food, so we can still walk and run even if we skip a meal.

The one thing I can do is switch off every light and fan when I leave a room. It costs nothing, it takes one second, and it saves electricity every single day.

Ask the owner or the driver how many kilometres the vehicle goes on one litre of petrol or diesel. Write the answers in a table. The vehicle that goes more kilometres on one litre uses less fuel for the same journey.

Sample answer — what my table looked like:

These are only sample figures. Write the real numbers you are told.

(the first is the book’s example):

Sample plan — my clean energy home: solar panels and a solar water heater on the roof, a small windmill, a solar cooker in the courtyard, LED bulbs, big windows on opposite walls for daylight and breeze, a clothes line in the sun, and shade trees.

Sample answer — My Energy Diary, Monday (one line each time energy is used, then a count):

My count for the day

What I will change: I used electricity the most — 6 times out of 13. Tomorrow I will switch off the fan and light whenever I leave a room.