Chapter-Five-Energy-and-Matter

PSC Elementary Science Note: Energy and Matter for Exam-2017

Energy and Matter: this is your fifth chapter. This chapter is very important and its length is also long. From the first chapter to the  fourth chapter, there is a subtle similarity in the subject matter. But this chapter is different from those chapters. Its subject matter is different and also hard to memorize. But don’t worry. I will try to present the answers in simple language. I won’t make the answers long in length unnecessarily. Not also for short answered questions, but also for descriptive questions, this chapter is very essential. We get many short and descriptive questions and MCQ also here. We don’t have the chance of denying this chapter. The questions of main text cannot cover the whole chapter. So you will get here more questions. These will help you to gather an idea that covers full chapter. And it will be beneficial to gain marks in MCQ.

At a Glance 

  1. Energy and forms of energy
  2. Sources of energy
  3. Transformation of energy
  4. Transfer of energy
  5. Proper Use and Saving of Energy
  6. Structure of Matter.

Short Answered Questions (Main Text)

1. Give 5 examples of forms of energy.
Ans: 5 examples of forms of energy are given below:
1. Electrical energy, mechanical energy, light energy, sound energy and chemical energy.

2. What are the three processes of heat transfer?
Ans: Three processes of heat transfer are given below:

  1. Conduction: Transfer of heat through solid matter is called conduction.
  2. Convection: Transfer of heat energy through the gases and liquids is called convection.
  3. Radiation: Radiation is the process in which energy is emitted from a source without any medium.

3. How does light travel? Or, How do we get light from Sun? ★

Ans: Light is the form of energy that helps us to see. Light travels as radiation. Light can transfer without any medium such as solids, liquids, and gasses. Light does not need any medium to transfer. Light can travel through space. This is how light from the Sun, the Moon, and stars reaches the Earth.

4. What is atom? ★
Ans: All matter is made up of very tiny particles that we cannot see with the naked eyes. Those tiny particles are called atom.

5. What form of energy does a guitar produce? ★
Ans: A guitar produces sound energy. The energy that helps us to hear is called sound energy. Sound comes from the vibration of objects. When we touch the string of a guitar, it vibrates and sound is produced from its vibration.

Descriptive Questions (Main Text)

1. What energy change takes place when you switched on a TV?
Ans: When we switch on TV, electrical energy is changed into light, heat and sound energy.

2. You hold a cup of ice water, and your hand becomes cold. Your friend says that it is cold because the cold from the cup moved to your hand. IS it correct or not? Explain why. ★
Ans: Yes, it is correct. It is cold because the cold from the cup moved to my hand. It is caused because of transfer of coldness. Transfer of heat through solid matter is called conduction. A cup is a solid matter. For ice water, my skin leaves temperature. And it gets cold with the touch of ice water.

3. How does heat travel when you cook rice in a pot? ★
Ans: At the time of cooking rice, heat transfers through convection. Transfer of heat energy through the gases and liquids is called convection. When we put a pot of water on a stove, the heated water near the bottom of the pot rises to the top of the water. Instead, the cold water near the top sinks to the bottom of the pot, and then it is heated and rises to the top. Through this process heat spread from top to bottom of the pot. This is the way, heat travels when we cook rice in a pot.

psc-elementary-science-convection-of-heat

Figuer: Convection of heat

4. How planting trees around house can save energy? ★
Ans: Saving energy is very important to protect our existence on Earth. By saving energy we can help to preserve energy resources and prevent pollutions.
1. Planting trees to help shade houses on hot summer days. So we feel less hot. It keeps us away from switching on fans. It helps to save non-renewable energy. Planting trees around house produce dried leaves which are used in cooking in villages. So use of oil, coal, and natural gas is decreased.

More Questions

1. What is energy?
Ans: Energy is the ability to do things. We use energy in everything that we do.

2. Give some important examples of different forms of energy? ★
Ans: Electrical Energy: This energy is used to run electrical appliances such as fan, TV, light, washing machine etc.
Mechanical energy: The form of energy that a moving object has. Wind can be an example of mechanical energy because it can run windmill. Energy of a moving car is also mechanical energy.
Light energy: The energy that can create different types of light and helps us to see is called light energy. It can pass through transparent matter. We get light energy from sun, electric light and candle etc.
Sound energy: The energy that helps us to hear is called sound energy. Sound comes from the vibration of objects. It travels through air or other matter. We use it to enjoy music.
Thermal (Heat) energy: Heat is a form of energy. We get heat energy from the fire of stove or electric iron.
Chemical energy: Chemical energy remains stored in food, fuel, coal etc.

3. What is mechanical energy?
Ans: The form of energy that a moving object has. Wind can be an example of mechanical energy because it can run windmill. Energy of a moving car is also mechanical energy.

4. What is sound energy?
Ans: The energy that helps us to hear is called sound energy. Sound comes from the vibration of objects. It travels through air or other matter. We use it to enjoy music.

5. What is light energy?
Ans: The energy that can create different types of light and helps us to see is called light energy. It can pass through transparent matter. We get light energy from sun, electric light and candle etc.

6. What type of energy do we get from food? ★
Ans: Chemical energy remains stored in food, fuel, coal etc. So we get chemical energy from food.

7. Explain Sun is the main source of energy? ★
Ans: Energy is used in various works in different ways. We get energy from different sources. Sometimes energy comes from coal, oil, or food and sometimes it comes from wind or water current. Sometimes we get energy from battery or generator. We get heat, light, electricity, sound energy from those sources. If we observe closely, we found that the main source of all energy is the sun.

8. What is energy transformation?
Ans: Energy can be changed from one form to another. The change of energy from one form to another is known as energy transformation.

9. Give some important examples of energy transformation? ★
Ans: We get solar energy directly as light and heat. But solar energy can changes its forms. When plants make food by themselves, they change the light energy from the Sun to chemical energy. When animals eat these plants as food, they change the stored chemical energy into heat and mechanical energy. Solar panels can change light energy into electrical energy. When we switch on TV, electrical energy is changed into light, heat and sound energy.

10. Give a best example of energy transformation. Or, Explain How does chemical energy change into mechanical energy through plants.
Ans: When plants make food by themselves, they change the light energy from the Sun to chemical energy. When animals eat these plants as food, they change the stored chemical energy into heat and mechanical energy.

11. What is conduction? Give an example.
Ans: Transfer of heat through solid matter is called conduction. If we place a metal spoon in the hot water, soon it begins to feel hot. This is because the spoon is heated by hot water, and then the heat spreads to the colder end of the spoon.
12. What is radiation? ★
Ans: Radiation is the process in which energy is emitted from a source without any medium. Conduction can work through solids, and convection can work through liquids and gases, but radiation can even work without any medium.

13. How can we feel the heat of the Sun even though it is millions of kilometres away in space? ★
Ans: Radiation is the process in which energy is emitted from a source without any medium. This is why we can feel the heat of the Sun even though it is millions of kilometres away in space. With the same process we feel the heat from fire or light bulbs.

14. Why is saving energy important?
Ans: We use energy in many works every day. Most of the energy we depend on comes from non-renewable energy resources such as oil, coal, and natural gas. They cannot be replaced once we use them up. Therefore, we have to use energy resources wisely. Wasting energy is not good for the environment. By saving energy we can help to preserve energy resources and prevent pollutions.

15. How do we save energy?
Ans: There are a few ideas to save more energy:

  1. Turn off lights and appliances when we are not using them.
  2. Do not leave the refrigerator door open any longer than you need to.
  3. Plant trees to help shade houses on hot summer days.
  4. Open the curtains and use the sunlight instead of turning on the lights.
  5. Walk or use bicycle instead of using car as much as possible.

17. What is molecule? ★
Ans: Two or more atom makes molecule.

18. What is matter?
Ans: A molecule is a group that is made up of two or more atoms joined together. A matter is the collection of innumerable molecules.
19. Explain the states of matter. Or, Explain the state of a matter depends on the arrangement and the bonding among the molecules of that matter. ★
PSC Elementary Science Chapter five three states-of-matter

Figure- three states of matter

Ans: Matter can exist in three states: solids, liquids and gasses. The state of a matter depends on the arrangement and the bonding among the molecules of that matter. Water is a matter and also consists of innumerable water molecules. Those molecules are always in motion. In solids like ice, water molecules are closely bound to one another in place. In liquids like water, the molecules are quite close together, but they have a little space to move around. In gases like vapour, the molecules are spread very far apart. They are randomly arranged and are constantly moving freely at high speed.

20. How a water molecule is consists of? ★
Ans:
A water molecule is consists of an oxygen atom and two hydrogen atoms.

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