Q1: What is a substance?

Answer: A substance is a form of matter that has a uniform and definite composition and distinct properties.

Q2: What are natural substances? Give examples.

Answer: Natural substances are materials that are found directly in nature. Examples include wood, cotton, wool, silk, clay, minerals, and water.

Q3: What are man-made substances? Give examples.

Answer: Man-made substances are materials that are produced by humans through chemical processes or by modifying natural substances. Examples include plastic, glass, paper, cement, and synthetic fabrics like nylon.

Q4: What is the main difference between natural and man-made substances?

Answer: Natural substances are obtained from nature, while man-made substances are created or synthesized by humans, often from natural raw materials.

Q5: Name some properties of wood that make it useful.

Answer: Wood is strong, durable, a good insulator, and can be easily cut and shaped, making it useful for furniture, building materials, and tools.

Q6: What are metals? Give examples of metals used in daily life.

Answer: Metals are generally hard, shiny, good conductors of heat and electricity, and can be hammered into sheets or drawn into wires. Examples: Iron (for tools, construction), Copper (for wires, utensils), Aluminium (for utensils, foils).

Q7: What are the properties of plastic? Why is it widely used?

Answer: Plastic is lightweight, durable, waterproof, flexible, and can be molded into various shapes. It is widely used because it is inexpensive, versatile, and resistant to corrosion.

Q8: What is glass made from? Name some uses of glass.

Answer: Glass is primarily made from sand (silica). It is used for windows, bottles, spectacles, mirrors, and laboratory equipment.

Q9: What are fabrics? Give examples of natural and synthetic fabrics.

Answer: Fabrics are materials made by weaving or knitting threads. Natural fabrics include cotton, wool, and silk. Synthetic fabrics include nylon, polyester, and rayon.

Q10: How is paper made? What are its uses?

Answer: Paper is mainly made from wood pulp. It is used for writing, printing, packaging, and making books and newspapers.

Q11: What is cement? What is it used for?

Answer: Cement is a powdery substance that, when mixed with water, sand, and gravel, forms concrete, a strong building material. It is primarily used in construction for buildings, roads, and bridges.

Q12: Why is it important to choose the right substance for a particular use?

Answer: It is important to choose the right substance because each substance has specific properties that make it suitable or unsuitable for a particular application. Using the wrong material can lead to inefficiency, damage, or danger.

Q13: What are biodegradable substances? Give an example.

Answer: Biodegradable substances are materials that can be broken down naturally by microorganisms in the environment. Example: Food scraps, paper, cotton clothes.

Q14: What are non-biodegradable substances? Give an example.

Answer: Non-biodegradable substances are materials that cannot be easily broken down by natural processes and remain in the environment for a very long time. Example: Plastic, glass, metals.

Q15: Why are non-biodegradable substances a concern for the environment?

Answer: Non-biodegradable substances are a concern because they accumulate in the environment, causing pollution (land, water), harming wildlife, and taking up valuable landfill space.

Q16: What is the concept of 'Reduce, Reuse, Recycle'?

Answer: 'Reduce, Reuse, Recycle' is a waste management hierarchy:

• Reduce: Use less of a product to minimize waste.
• Reuse: Use items again for the same or a different purpose instead of discarding them.
• Recycle: Process used materials into new products to prevent waste of potentially useful materials.

Q17: How can we reduce the use of plastic in our daily lives?

Answer: We can reduce plastic use by carrying reusable bags, using refillable water bottles, choosing products with less packaging, and avoiding single-use plastic items.

Q18: What is the importance of recycling?

Answer: Recycling is important because it conserves natural resources, saves energy, reduces landfill waste, and decreases pollution.

Q19: Name some items that can be recycled.

Answer: Items that can be recycled include paper, cardboard, plastic bottles, glass bottles, aluminum cans, and certain types of metals.

Q20: What are ceramics? Give an example of their use.

Answer: Ceramics are hard, brittle, heat-resistant, and corrosion-resistant materials made by shaping and firing a non-metallic mineral, such as clay. Examples: Pottery, tiles, bricks, sanitaryware.

Q21: What is the difference between opaque, translucent, and transparent substances?

Answer:

• Opaque: Does not allow light to pass through (e.g., wood, metal).
• Translucent: Allows some light to pass through but scatters it, so objects cannot be seen clearly (e.g., frosted glass, butter paper).
• Transparent: Allows light to pass through clearly, so objects can be seen distinctly (e.g., clear glass, pure water).

Q22: Why is cotton a popular fabric for summer clothes?

Answer: Cotton is popular for summer clothes because it is soft, breathable, and absorbs moisture (sweat) well, helping to keep the body cool and comfortable.

Q23: Why is wool preferred for winter clothes?

Answer: Wool is preferred for winter clothes because it is a good insulator, trapping air and keeping the body warm, and it is also durable and moisture-wicking.

Q24: What are the properties of rubber?

Answer: Rubber is elastic, waterproof, and a good insulator. It is used for tires, gloves, and elastic bands.

Q25: How does knowing the properties of substances help us in daily life?

Answer: Knowing the properties of substances helps us choose the right materials for specific tasks, understand why certain objects are made of particular materials, and use them safely and effectively.

Q26: What is the importance of proper waste disposal?

Answer: Proper waste disposal is important to prevent pollution, maintain hygiene, control diseases, and protect the environment from harmful substances.

Q27: How are natural substances converted into man-made substances?

Answer: Natural substances are converted into man-made substances through various industrial processes and chemical reactions, where their structure is altered or new compounds are formed (e.g., wood to paper, petroleum to plastic).