NCERT Solutions Class 5 EVS Our Wondrous World Chapter 07 Energy How Things Work

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Question. What is Energy?
Answer: Energy allows things to move, give off light, create sound, or become hot or cold. For example, a fan moves due to electrical energy, a bulb shines because of light energy, and we have the ability to run and play because food supplies us with energy. Without energy, nothing would be able to happen in the world around us.
In simple words: Energy is what makes things work. A fan needs electricity, a light needs electricity to shine, and our body needs food to give us power to move and play.

Exam Tip: Define energy with clear examples of movement, light, sound, and heat - examiners look for real-life applications, not just the textbook definition.

Question. Let us observe a kitchen for some time. Write your observations and the questions that come to your mind in the table given below.
Answer:

In simple words: When you watch a kitchen, you see things happening - food cooking, water heating, flames burning, and the fridge staying cold. Each of these things uses energy in different ways.

Exam Tip: Make observations of things you actually see and then ask simple, curious questions about why they happen - this shows clear understanding of cause and effect.

Question. Similarly, we observe different kinds of activities in nature and society. From your observation write down at least three things that you have noticed.
Answer:

Things that are Moving:
Leaves moving when the wind blows, a bird flying in the sky, a bicycle moving on the road.

Things that are Providing Light:
The Sun shining during the day, a bulb glowing in the room, a candle burning during a power cut.

Things that are Making a Sound:
Birds chirping early in the morning, a school bell ringing, a pressure cooker whistling in the kitchen.

Things that are Making Things Cool:
A fan blowing cool air, a refrigerator keeping food cold, an air conditioner cooling a room.

Things that are Making Things Hot:
Gas stove heating a pot, the Sun warming the ground, an iron rod getting hot in fire.
In simple words: We can sort all the activities we see into groups - things that move, things that give light, things that make sound, things that keep cool, and things that make warm. Energy helps everything in each group happen.

Exam Tip: Provide at least one clear example for each category - variety in your examples (nature, home, school) shows wider observation and understanding.

Question. Discuss: What makes these things move, shine, make a sound or get warm and cold?
Answer: These things move, shine, make sound or get warm and cold because of energy. Energy allows everything around us to work. Fans move due to electrical energy, bulbs shine due to light energy, drums make sound due to sound energy, the Sun makes things warm due to heat energy, and refrigerators make things cold using electrical energy. Therefore, energy is necessary for all activities to take place.
In simple words: Every action we see - things moving, shining, making noise, or changing temperature - happens because energy is making it work.

Exam Tip: Link each activity directly to its energy source - this connection is what examiners want to see in your answer, not just listing the activities.

Question. Think: What would you change in the activity to make the toy move faster or slower?
Answer: To make the toy (balloon) move faster, I would put more air into the balloon. This makes the balloon larger, and when more air rushes out, the balloon will move faster. To make the toy move slower, I would put less air into the balloon. Since less air will come out slowly, the balloon will move slower. The speed changes based on the amount of air we fill inside the balloon.
In simple words: More air makes the balloon go faster, and less air makes it go slower. The amount of air you put in changes how fast it goes.

Exam Tip: Explain the cause-and-effect relationship clearly - show how changing the amount of air causes a change in speed, not just stating what happens.

Question. Think: What happens if you use thinner or thicker rubber bands? Do they sound different?
Answer: When using thinner rubber bands, the sound becomes sharp and high. When using thicker rubber bands, the sound becomes deep and low. Yes, they do sound different because thin and thick rubber bands vibrate in different ways.
In simple words: Thin rubber bands make high, sharp sounds. Thick rubber bands make deep, low sounds. The difference comes from how they shake and move.

Exam Tip: Mention the specific property (thickness) that causes the difference and describe both the change in sound and the reason (vibration) clearly.

Question. Think: What do cars and scooters need to keep running?
Answer: Cars and scooters need fuel such as petrol and diesel to keep running. Vehicles move when they get energy from fuel. Therefore, cars and scooters work because they get energy from petrol and diesel.
In simple words: Cars and scooters need petrol or diesel to work. The fuel gives them the energy they need to move.

Exam Tip: Always connect the fuel directly to energy - show that fuel is a source of energy, not just something that "makes cars run."

Question. Write: How is food cooked in your house?
Answer: In my house, we use cooking gas (LPG) to cook food on the gas stove. My grandmother sometimes uses a wood-burning chulha to cook rotis. We have an electric induction cooktop for making dal and rice. During power cuts, we use a kerosene stove for cooking.
In simple words: Our home uses different ways to cook - gas stove is the main way, but we also use a wood stove, an electric cooktop, and a kerosene stove when needed.

Exam Tip: Include multiple methods of cooking to show you understand different fuel sources - this variety demonstrates broader knowledge of energy sources in daily life.

Question. Discuss: What kind of fuel do you use at home for cooking?
Answer: At home, we use the following fuels for cooking:
- LPG (Liquefied Petroleum Gas) cylinders
- Cooking gas from pipeline
- Wood and coal (in some rural areas)
- Kerosene stoves
- Electric stoves and induction cooktops
In simple words: Different homes use different fuels - some use gas cylinders, some use piped gas, some burn wood or coal, some use kerosene, and some use electricity.

Exam Tip: Show awareness of different fuel types used across different regions and situations - this demonstrates that you understand various energy sources exist for the same purpose.

Question. Discuss: What are the problems using too much wood or coal?
Answer: Using too much wood or coal creates several problems. A lot of smoke is produced, which pollutes the air. It causes breathing problems and cough in people. The kitchen walls become black with soot. It also contributes to deforestation. These fuels produce harmful gases and can cause fires if not handled properly.
In simple words: Burning wood or coal makes smoke that pollutes air, hurts our lungs, makes walls dirty, destroys forests, and can start fires.

Exam Tip: Connect each problem to either health, environmental, or safety concerns - grouping the impacts this way shows deeper understanding than just listing problems.

Question. Activity 5: Walk around your home or classroom. Identify five things that run on electricity. Fill in the following table.
Answer:

In simple words: Different electrical devices in our home do different jobs - some move, some give light, some make sound, some cool things, and some make heat.

Exam Tip: Match each device to what type of energy it uses or produces - this connection shows you understand how electricity transforms into different forms of energy.

Question. Think: What would your day be like if there was no electricity at all?
Answer: If there was no electricity at all, my day would be very hard to manage. I would wake up without an alarm clock to help me. The house would be dark at night since there would be no lights. I would not be able to watch television or use a fan during hot weather. My parents could not work on the computer or charge their mobile phones. At school, we would not be able to use smart boards or fans. Food kept in the refrigerator would spoil quickly. Doing homework at night would be difficult because there would be little light. Life without electricity would be slow and uncomfortable in every way.
In simple words: Without electricity, everything becomes hard - no lights, no fans, no computers, no charging phones, food goes bad, and everything takes much longer to do.

Exam Tip: Provide specific examples from different parts of your day (morning, school, evening) to show how electricity affects multiple areas of life, not just one or two things.

Question. Think: Place a small damp cloth in the Sun. Keep another damp cloth in the shade. Which one do you think will dry first? Why?
Answer: The damp cloth kept in the Sun will dry first. This happens because the Sun gives heat energy. The heat from the Sun helps the water in the cloth to evaporate faster. The cloth kept in the shade receives less heat, so it will take a longer time to dry.
In simple words: The cloth in the Sun dries faster because the Sun's heat makes the water disappear quickly. The cloth in shade gets less heat, so it dries slowly.

Exam Tip: Connect the speed of drying directly to the amount of heat energy received - showing this cause-and-effect relationship is what examiners look for.

Question. Think: Have you even seen papads being dried in the sunlight and clothes hung out to dry?
Answer: Yes, I have seen papads being dried in the sunlight and clothes hung out to dry. My grandmother spreads papads on the terrace in sunlight to make them crisp and dry. We hang wet clothes on clotheslines in places where the sun's heat energy evaporates the water and dries them completely. This shows how we use clean solar energy in our daily lives without needing electricity.
In simple words: People dry papads and clothes in the sun all the time. The sun's heat makes them dry without using electricity.

Exam Tip: Mention specific examples from your own home or community and link them to solar energy - personal observation combined with energy awareness scores well.

Question. Write: Can you think of more examples where we use the Sun, the wind or the flowing water?
Answer: Examples where we use Sun, wind or flowing water:

Sun energy:
- Drying clothes on clothesline
- Drying grains and vegetables
- Solar water heaters

Wind energy:
- Flying kites
- Sailing boats
- Winnowing grains
- Windmills for grinding flour

Flowing Water energy:
- Water mills for grinding grains
- Washing clothes in flowing river
- Hydroelectric power plants
- Water wheels for irrigation
In simple words: We use natural energy from the sun (heat), wind (moving air), and water (flowing movement) in many ways - drying food, sailing boats, grinding grain, and making electricity.

Exam Tip: Organize your answer by energy source rather than listing randomly - this shows clear thinking and helps the examiner see you understand how different natural sources serve different purposes.

Question. Activity: List actions that you see in the picture above and fill in the following table.
Answer:

In simple words: Every activity in the picture uses energy from somewhere - food powers people and animals, sun dries clothes and turns windmills, electricity lights the street, and fuel moves cars.

Exam Tip: Match the correct energy source to each activity - knowing the source for each action shows you understand energy transformation in the real world.

Question. What will happen if there is no electricity in your house for a day?
Answer: If there is no electricity in my house for a day, several things will happen. Lights will not work, so the house will be dark at night. Fans and coolers will not work, making it very hot and uncomfortable. Television and computer cannot be used for entertainment or work. Mobile phones will not get charged, leaving us without communication. The refrigerator will not work and food may spoil quickly. Studying at night will become difficult without proper lighting. Daily work and activities will become slow and uncomfortable because we depend on electricity for almost everything.
In simple words: Without electricity for one day, our home becomes dark, hot, boring, and uncomfortable. We can't use phones, computers, fans, or keep food cold.

Exam Tip: Cover multiple areas of daily life (lighting, cooling, entertainment, communication, food storage) to show how much we depend on electricity - this breadth of thinking gets full marks.

Question. Why is it better to use solar or wind energy instead of coal?
Answer: Solar and wind energy do not cause pollution, which is a major advantage over coal. They do not produce smoke or harmful gases. Coal causes severe air pollution when it is burned, which damages the environment and our health. Solar and wind energy will not get used up - they are renewable. Coal is limited and can finish one day. Using solar and wind energy helps protect the environment for future generations.
In simple words: Solar and wind energy are clean and never run out. Coal makes pollution, harms air, and will finish someday. Clean energy is better for Earth.

Exam Tip: Mention both environmental and resource-related advantages - pollution, health, and sustainability are all key reasons examiners look for in energy comparisons.

Question. Give two examples where you have seen energy being stored.
Answer: Energy is stored in a battery and is used to run a torch or remote control. We can use the stored electrical energy whenever we need it. Energy is also stored in food, which gives us the power to work, play and study throughout the day. When we eat food, our body releases that stored energy and uses it for movement and thinking.
In simple words: A battery stores electricity for flashlights and remote controls. Food stores energy that our body uses to move and think.

Exam Tip: Explain where the energy is stored and how it is used later - this shows you understand energy storage as a process, not just naming the storage medium.

Question. What is the one thing you can do at home to save energy?
Answer: There are many things I can do at home to save energy. I can switch off lights and fans when they are not needed. I can use LED bulbs instead of regular bulbs because they use less electricity. I should not keep the refrigerator door open for long periods. I can use stairs instead of a lift when possible. I can dry clothes in the sun instead of using an electric dryer. I can unplug chargers when they are not in use so they don't waste energy.
In simple words: Turn off lights and fans, use LED bulbs, keep the fridge door closed, use stairs not lifts, dry clothes in sun, and unplug chargers.

Exam Tip: Provide multiple practical examples that students can actually do at home - variety shows you have really thought about energy conservation in daily life.

Question. Find out how many kilometres a vehicle travels per litre of petrol or diesel. Ask about different vehicles. How will you compare them?
Answer: Different vehicles travel different distances per litre of fuel:
- Motorcycle: 40-60 km per litre
- Small car: 15-25 km per litre
- Bus: 3-6 km per litre
- Truck: 2-4 km per litre

Comparison: Heavy vehicles like trucks and buses use more fuel per kilometre travelled. Lighter vehicles with smaller engines travel a greater distance using the same amount of petrol or diesel, making them more economical. Lighter vehicles are also better for the environment because they use less fuel and produce fewer harmful gases.
In simple words: Motorcycles go farthest on one litre of fuel. Cars go less far. Trucks and buses use lots of fuel for short distances. Lighter vehicles are cheaper and cleaner.

Exam Tip: Include the comparison reasoning - explain why lighter vehicles are more efficient, not just state the numbers - this analysis is what separates good answers from excellent ones.

Question. Look around your home or classroom. List three objects that use energy and mention their source of energy. For example: Object; Energy Source: Electricity
Answer: Three objects that use energy and their sources:
- Fan - Electricity
- Bicycle - Food (human energy)
- Gas stove - LPG/Natural Gas
- Solar calculator - Sun energy
- Car - Petrol/Diesel
In simple words: Different objects around us need energy to work - fans need electricity, bicycles need food to power people, stoves need gas, and cars need fuel.

Exam Tip: Show variety in your examples - choose objects that use different energy sources (electricity, fuel, food, sun) to demonstrate broad understanding of energy sources in daily life.

Question. Create and Share: (a) Draw or make a simple plan of a 'clean energy home' that use solar, wind or any such source of energy.
Answer: A clean energy home plan should include:
- Solar panels on the roof for generating electricity
- Solar water heater for providing hot water
- Windows placed strategically to allow natural light to enter
- Wind chimes or a small windmill in the garden to use wind power
- Rainwater harvesting system to collect and store water
- Energy-efficient appliances that use less power
In simple words: A clean energy home uses solar panels for electricity, solar heaters for hot water, big windows for light, windmills for wind power, and saves rainwater.

Exam Tip: Design your home to use multiple renewable energy sources, not just one - this shows you understand that different clean energies can be used together.

Question. Create and Share: (b) Make 'my energy diary' for one day, record the number of times you have used the electricity fuel and so on.
Answer: My Energy Diary:

Morning:
- Used electricity: 3 times (lights, fan, phone charging)
- Used gas: 1 time (cooking breakfast)
- Used sun energy: 1 time (drying clothes)

Afternoon:
- Used electricity: 4 times (fan, TV, mixer, lights)
- Used fuel: 1 time (car for going to market)

Evening:
- Used electricity: 5 times (lights, fan, TV, phone charging, electric kettle)
- Used gas: 1 time (cooking dinner)

Total for the day:
- Electricity - 12 times
- Gas - 2 times
- Fuel - 1 time
- Sun - 1 time
In simple words: During one day, I use electricity the most (12 times), then gas twice for cooking, and also car fuel and sun energy once.

Exam Tip: Track multiple energy sources throughout the entire day to show you understand that we use many different types of energy at different times - this real-life tracking demonstrates practical awareness of energy consumption.