Class 8 Science Worksheet - Materials-Metals and Non-Metals Part B ... - Free Printable

Let's solve the questions step by step and provide explanations for each.

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III. Fill in the blanks

1. The number of metals is much ________ than non-metals.
✔ Answer: *greater*
🔍 Explanation: In the periodic table, there are more metals (about 90) than non-metals (about 20). Most elements are metals.

2. The smallest unit of an element is known as ________________.
✔ Answer: *atom*
🔍 Explanation: An atom is the smallest particle of an element that retains its chemical properties.

3. Metals like __________ and __________ exist in liquid state.
✔ Answer: *Mercury* and *Gallium*
🔍 Explanation: Mercury (Hg) is a metal that is liquid at room temperature. Gallium (Ga) also melts just above room temperature (~29.76°C), so it can be liquid under normal conditions.

4. Elements which do not react chemically are known as ________________.
✔ Answer: *Noble gases*
🔍 Explanation: Noble gases (like He, Ne, Ar) have complete valence shells and are chemically inert.

5. Oxides of metals which are acidic as well as basic in nature are called ________ oxides.
✔ Answer: *Amphoteric*
🔍 Explanation: Amphoteric oxides can act as both acidic and basic depending on the reaction. Example: Al₂O₃ (aluminum oxide).

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IV. Multiple Choice Questions

1. Pb is the symbol of
a. Copper
b. Phosphorus
c. Lead
✔ Answer: *c. Lead*
🔍 Explanation: Pb comes from the Latin word *Plumbum*, meaning lead.

2. Helium, Neon, Argon are
a. Metals
b. Noble gases
c. Metalloids
✔ Answer: *b. Noble gases*
🔍 Explanation: These are all gases in Group 18 of the periodic table, known for their low reactivity.

3. Which of the following metal burns with dazzling white flame?
a. Sodium
b. Potassium
c. Magnesium
✔ Answer: *c. Magnesium*
🔍 Explanation: Magnesium burns with a bright white light, often used in fireworks and flares.

4. Which of the following displaces Hydrogen on reaction with dilute mineral acids?
a. Silver
b. Sodium
c. Sulphur
✔ Answer: *b. Sodium*
🔍 Explanation: Sodium is highly reactive and reacts vigorously with dilute acids to produce hydrogen gas. Silver does not displace H₂; sulfur is a non-metal.

5. Metals which are used for making electric wires and cooking vessels—
a. Copper and Aluminum
b. Copper and Iron
c. Aluminum
✔ Answer: *a. Copper and Aluminum*
🔍 Explanation: Copper is excellent for electrical conductivity (wires), and both copper and aluminum are used in cookware due to good heat conduction.

6. Non-metals which is used in making microchips
a. Carbon
b. Silicon
c. Sulphur
✔ Answer: *b. Silicon*
🔍 Explanation: Silicon is a semiconductor and is the primary material used in manufacturing microchips and electronic devices.

7. Metals which can be cut with knife.
a. Iron
b. Calcium
c. Sodium
✔ Answer: *c. Sodium*
🔍 Explanation: Sodium is very soft and can be easily cut with a knife. Iron and calcium are harder.

8. Compounds of which non-metal are used as fertilizers?
a. Chlorine
b. Nitrogen
c. Phosphorus
✔ Answer: *b. Nitrogen*
🔍 Explanation: Nitrogen-based compounds (like ammonium nitrate, urea) are commonly used in fertilizers. Phosphorus is also used, but nitrogen is more widespread. However, since only one answer is allowed and nitrogen is a major component, b. Nitrogen is best.

⚠️ Note: Both nitrogen and phosphorus are important in fertilizers, but nitrogen is most commonly associated with fertilizer use.

9. Alloys of which of the following metal are used for making aeroplanes and automobile engines?
a. Copper
b. Aluminum
c. Iron
✔ Answer: *b. Aluminum*
🔍 Explanation: Aluminum alloys are lightweight and strong, ideal for aircraft and car parts. Iron (as steel) is also used, but aluminum is preferred where weight reduction is critical.

10. Metals react with oxygen to form their oxides which are generally:
a. Neutral in nature
b. Acidic in nature
c. Basic in nature
✔ Answer: *c. Basic in nature*
🔍 Explanation: Metal oxides are typically basic. For example, CaO (calcium oxide) reacts with water to form Ca(OH)₂, a base.

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✔ Final Answers Summary:

#### Fill in the Blanks:
1. greater
2. atom
3. Mercury, Gallium
4. Noble gases
5. Amphoteric

#### Multiple Choice:
1. c. Lead
2. b. Noble gases
3. c. Magnesium
4. b. Sodium
5. a. Copper and Aluminum
6. b. Silicon
7. c. Sodium
8. b. Nitrogen
9. b. Aluminum
10. c. Basic in nature

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