Grade 5 Q&A: Chapter 24: Substances, Objects and Energy

Concept Questions

Q1: What is a substance?

Answer: A substance is the material of which an object is made. For example, wood is a substance.

Q2: What is an object?

Answer: An object is something that has a definite shape and can be seen or touched. For example, a chair is an object.

Q3: What is the main difference between a substance and an object?

Answer: A substance is the material (like wood or glass), while an object is the thing made from that material (like a chair or a glass).

Q4: Name the three states in which substances can exist.

Answer: The three states are solid, liquid, and gas.

Q5: Describe the characteristics of a solid.

Answer: A solid has a definite shape and a definite volume. It does not change its shape easily. Examples include a stone or a book.

Q6: Describe the characteristics of a liquid.

Answer: A liquid does not have a definite shape, but it has a definite volume. It takes the shape of the container it is poured into. Examples include water or milk.

Q7: Describe the characteristics of a gas.

Answer: A gas does not have a definite shape or a definite volume. It spreads out to fill the entire container it is in. Examples include air or water vapour.

Q8: What is melting?

Answer: Melting is the process where a solid changes into a liquid, usually when it gains heat. For example, ice melting into water.

Q9: What is evaporation?

Answer: Evaporation is the process where a liquid changes into a gas, usually when it gains heat. For example, water turning into steam.

Q10: What is condensation?

Answer: Condensation is the process where a gas changes into a liquid, usually when it loses heat. For example, steam turning into water droplets.

Q11: What is freezing?

Answer: Freezing is the process where a liquid changes into a solid, usually when it loses heat. For example, water turning into ice.

Q12: Define energy.

Answer: Energy is the ability to do work. Without energy, nothing can move or change.

Q13: Name three forms of energy.

Answer: Three forms of energy are heat energy, light energy, and electrical energy.

Q14: What is chemical energy?

Answer: Chemical energy is the energy stored in substances like food, fuels (petrol, diesel), and batteries. It is released when these substances undergo chemical changes.

Q15: How does heat energy help us in daily life?

Answer: Heat energy helps us in many ways, such as cooking food, keeping warm, and drying clothes.

Application-Based Questions

Q16: If you leave an ice cube out on a warm day, what change of state occurs? Explain.

Answer: If you leave an ice cube out on a warm day, **melting** occurs. The ice cube, which is solid, gains heat from the warm air and changes into water, which is a liquid.

Q17: Your mother is boiling water for tea. What change of state is happening when steam comes out from the kettle?

Answer: When steam comes out from the kettle, **evaporation** is happening. The boiling water (liquid) gains enough heat to turn into steam (gas).

Q18: Why do we feel tired after a lot of physical activity? Which form of energy is used?

Answer: We feel tired after a lot of physical activity because our body uses up the **chemical energy** stored in the food we eat. This chemical energy is converted into **mechanical energy** for movement and also produces heat.

Q19: Why does a fan rotate when you switch it on? Which form of energy is converted?

Answer: A fan rotates when you switch it on because **electrical energy** is supplied to it. This electrical energy is then converted into **mechanical energy** to make the fan blades move.

Q20: Give an example of how one substance can be used to make multiple objects.

Answer: One example is **plastic**. Plastic can be used to make many different objects like bottles, toys, chairs, and containers.

Q21: Give an example of how one object can be made from multiple substances.

Answer: One example is a **bicycle**. A bicycle is an object made from multiple substances like metal (for the frame), rubber (for the tires), and plastic (for some parts like grips or reflectors).

Q22: A car uses petrol to move. What form of energy is stored in petrol and what form is it converted into?

Answer: **Chemical energy** is stored in petrol. When the petrol burns in the car's engine, it is converted mainly into **mechanical energy** to make the car move, and also into heat and sound energy.

Q23: Why are droplets formed on the outside of a cold glass of water on a hot day?

Answer: Droplets are formed due to **condensation**. The water vapour (gas) in the warm air around the cold glass loses heat when it touches the cold surface of the glass, turning back into tiny water droplets (liquid).

Q24: You see a candle burning. What changes in state are occurring?

Answer: When a candle burns, the solid wax near the flame melts into liquid wax (melting). This liquid wax then turns into a gas (evaporation) which burns, producing light and heat. So, both melting and evaporation are occurring.

Q25: Why is it important to conserve energy?

Answer: It is important to conserve energy because many of our energy sources, like coal and natural gas, are limited and take millions of years to form. Conserving energy helps these resources last longer and also reduces pollution.

Higher-Order Thinking Questions

Q26: "Energy cannot be created or destroyed, but it can be changed from one form to another." Explain this statement with an example from daily life.

Answer: This statement means that the total amount of energy in the universe remains constant; it just transforms from one type to another. For example, when you switch on an electric bulb, the **electrical energy** is not destroyed. Instead, it is converted into **light energy** (which helps us see) and **heat energy** (which makes the bulb warm). No energy is lost, it simply changes its form.

Q27: Discuss how the sun is the ultimate source of various forms of energy on Earth.

Answer: The sun is the ultimate source of almost all energy on Earth. It provides **light energy** (for seeing) and **heat energy** (for warmth and drying). Plants use the sun's light energy to make food (chemical energy), which animals then eat. Fossil fuels like coal and petrol were formed from ancient plants and animals, storing the sun's energy. The sun's heat also drives the water cycle, creating rain and rivers that can be used for hydroelectric power (mechanical/electrical energy). Even wind energy is caused by uneven heating of the Earth by the sun.

Q28: Imagine you are building a house. How would your choice of building materials relate to the concepts of "substance" and "object"?

Answer: When building a house, you choose various **substances** like wood, cement, bricks, and sand. These substances are then used to create different **objects** that make up the house. For example, wood (substance) is used to make doors and window frames (objects). Cement and bricks (substances) are used to build walls (objects). Understanding the properties of each substance (e.g., strength of cement, insulation of wood) helps in choosing the right materials for each object in the house.

Q29: If there were no energy, what would life on Earth be like?

Answer: If there were no energy, life on Earth as we know it would be impossible. Nothing would move or change. There would be no light or heat from the sun, no wind, no flowing water, and no growth in plants or animals. Our bodies wouldn't be able to function, and all life processes would stop. It would be a completely still, dark, and lifeless planet.

Q30: How do changes in the state of water play a crucial role in the water cycle?

Answer: Changes in the state of water are fundamental to the water cycle. Water from oceans, rivers, and lakes (liquid) **evaporates** into water vapour (gas) due to the sun's heat. This water vapour rises, cools, and **condenses** to form clouds (liquid droplets or ice crystals). When these droplets become heavy, they fall as rain or snow (precipitation), which is water in liquid or solid form. This water then flows back to water bodies, and the cycle repeats, showing how water continuously changes its state to sustain life on Earth.

References

1. Maharashtra State Board Environmental Studies (Part One) Standard Five Textbook (2015 Edition) - Chapter 24: Substances, Objects and Energy, pages 127-132.
2. Maharashtra State Board 5th Standard Environmental Studies Syllabus.
3. Balbharati Environmental Studies Part 1 Textbook.