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Class 10 Science: Metals and Non-metals, 8 practice questions with answers

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These are 8 practice questions on NCERT Class 10 Science Chapter 3, Metals and Non-metals, each with a short answer and the textbook page it comes from. They cover conduction, how metals react with air and with acids, how a metal atom becomes an ion, and the carat scale for gold. Try each one before you read the answer.

These questions are our own, drafted with AI help. Every number was re-computed by a test script and every statement was checked against the chapter, but no practising teacher has reviewed them yet. If you find a mistake, please tell us.

Properties of metals

Question 1. Which two metals are the best conductors of heat? (Silver and copper; lead and mercury; or sodium and potassium.)

Answer: silver and copper. The best conductors of heat are silver and copper; lead and mercury are comparatively poor conductors of heat. (Page 38.)

Question 2. Why is pure gold mixed with silver or copper before jewellery is made from it? (Pure gold is very soft; pure gold rusts quickly; or pure gold does not shine.)

Answer: pure gold is very soft. Pure gold, known as 24 carat gold, is very soft and not suitable for making jewellery, so it is alloyed with silver or copper to make it hard. (Page 54, "Do You Know?".)

Question 3. 22 carat gold has 22 parts of pure gold in every 24 parts. What percentage of it is pure gold, to one decimal place?

Answer: 91.7%. 22 ÷ 24 × 100 = 91.66…, which is about 91.7%. The other 2 parts are silver or copper; the textbook says 22 carat gold is generally used for ornaments in India. (Page 54.)

Question 4. Gold purity is given in carats: 24 carat is pure gold, and an 18 carat alloy has 18 parts of gold in every 24 parts. A ring weighs 10 g and is 18 carat. (a) How much pure gold is in it? (b) How much of the other metal? (c) How many grams of pure gold must be melted in with it to make the whole lump 22 carat?

Answer: (a) 10 × 18/24 = 7.5 g of gold. (b) 10 − 7.5 = 2.5 g of other metal. (c) Adding x g of gold: (7.5 + x) ÷ (10 + x) = 22/24, so 24(7.5 + x) = 22(10 + x), 180 + 24x = 220 + 22x, and x = 20 g. Check: 27.5 g of gold in 30 g is 22/24. (The carat scale and the 22 carat figure are on page 54; the working is ours.)

Reactions of metals

Question 5. Assertion (A): Sodium and potassium are stored under kerosene. Reason (R): They react so strongly with oxygen that they can burst into flames in open air. Choose the correct option: both true and R explains A; both true but R does not explain A; A true and R false; or A false and R true.

Answer: A and R are both true, and R explains A. Potassium and sodium react so vigorously that they catch fire if kept in the open, so to protect them and prevent accidental fires they are kept immersed in kerosene oil. (Section 3.2.1, page 42.)

Question 6. Zinc granules are added to dilute hydrochloric acid. What are the products of a metal reacting with a dilute acid in general?

Answer: a salt and hydrogen gas. Metal + dilute acid → salt + hydrogen. Here, zinc chloride and hydrogen. (Page 44.)

Ionic compounds and alloys

Question 7. A magnesium atom (electrons 2, 8, 2) becomes the ion Mg²⁺ in magnesium chloride. How many electrons does it lose?

Answer: 2. It gives away its 2 outer electrons, reaching the stable 2, 8 arrangement and a charge of 2+. The textbook shows Mg → Mg²⁺ + 2e⁻ (magnesium cation) for the formation of magnesium chloride. (Figure 3.6, page 48.)

Question 8. What is an alloy of a metal with mercury called?

Answer: an amalgam. An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal; if one of the metals in it is mercury, the alloy is known as an amalgam. (Page 54.)

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Sources

All opened and read on 21 October 2026. Page numbers are the printed page numbers of the textbook.

The definitions and facts are from the textbook pages above. The questions, worked answers and checks are our own, and every number was re-computed by script. This guide is general information; follow your teacher and the textbook.