Imp Questions For All Chapters – General Science Class 7
Elements, Compounds and Mixtures
Short Questions
1. How many states of matter are there? Name them.
→ There are three states of matter: solid, liquid, and gas.
2. What causes a change in the state of matter?
→ Heat or pressure can change the state of matter.
3. What is matter?
→ Anything that has mass and occupies space is called matter.
4. What are the two main properties of matter?
→ Mass and volume are the two main properties of matter.
5. Give two examples of natural elements.
→ Oxygen (O) and Iron (Fe) are natural elements.
6. What is an element?
→ A substance made up of only one type of atom is called an element.
7. What is a compound?
→ A substance made up of two or more elements chemically combined is a compound.
8. Give an example of a compound.
→ Water (H₂O) is a compound made of hydrogen and oxygen.
9. What is a mixture?
→ A combination of two or more substances that are not chemically combined is a mixture.
10. What is the difference between an element and a compound?
→ An element has only one type of atom, while a compound has two or more different atoms combined.
11. Name one metal and one non-metal.
→ Metal: Iron (Fe), Non-metal: Oxygen (O).
12. What is an alloy?
→ A mixture of two or more metals is called an alloy, like steel and brass.
13. What is rusting?
→ When iron reacts with water and oxygen, it forms rust (iron oxide), which is a chemical change.
14. What is the smallest particle of an element?
→ The atom is the smallest particle of an element.
15. What is the symbol of Sodium and Potassium?
→ Sodium (Na), Potassium (K).
16. What are metalloids?
→ Elements that have properties of both metals and non-metals are metalloids (e.g., Silicon, Arsenic).
17. What is distillation used for?
→ Distillation is used for purifying liquids, like separating salt from seawater.
18. What is chromatography?
→ Chromatography is a method used to separate different colors in ink or dyes.
19. What is the purpose of centrifugation?
→ Centrifugation is used to separate heavier particles from liquids, like butter from buttermilk.
20. How can we prevent rusting?
→ Rusting can be prevented by painting, galvanizing, or oiling iron surfaces.
Long Questions
1. How are elements, compounds, and mixtures different?
→ An element has only one type of atom (e.g., oxygen). A compound has two or more elements chemically combined (e.g., water). A mixture is a combination of different substances without chemical bonding (e.g., air).
2. What are metals and non-metals? Give examples.
→ Metals are shiny, conduct electricity, and can be shaped (e.g., gold, iron). Non-metals do not conduct electricity and are brittle (e.g., oxygen, sulfur).
3. How are alloys useful?
→ Alloys are stronger and more durable than pure metals. For example, steel (iron + carbon) is used in buildings, and brass (copper + zinc) is used in musical instruments.
4. What happens when a magnesium ribbon is burned?
→ Magnesium burns in air to form magnesium oxide (MgO), which is a white ash, showing a chemical change.
5. Why is saltwater a mixture and not a compound?
→ Saltwater is a mixture because salt and water are not chemically bonded and can be separated by evaporation.
6. What is the role of a separating funnel?
→ A separating funnel is used to separate two liquids that do not mix, like oil and water.
7. How is butter separated from buttermilk?
→ Butter is separated from buttermilk using centrifugation, where spinning separates lighter butter from the liquid.
8. How does distillation purify water?
→ In distillation, water is heated into vapor, leaving impurities behind, and then the vapor is cooled back into pure water.
9. Why is chromatography important?
→ Chromatography helps to separate different colors in dyes and detect chemicals in substances, used in forensics and medicine.
10. Why is iron coated with zinc?
→ Iron is coated with zinc to prevent rusting, a process called galvanization, which protects it from moisture and air.
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