GSEB Class 8 Science Solutions Chapter 4 Materials Metals and Non-Metals

Question 1. Which of the following can be beaten into thin sheets?
(a) Zinc
(b) Phosphorus
(c) Sulphur
(d) Oxygen
Answer: (a) Zinc
In simple words: Zinc is a metal that can be hammered or pressed into thin sheets without breaking, a property known as malleability.

Exam Tip: Remember that metals are generally malleable (can be beaten into sheets) and ductile (can be drawn into wires), while non-metals usually lack these properties.

Question 2. Which of the following statements is correct?
(a) All metals are ductile.
(b) All non-metals are ductile.
(c) Generally, metals are ductile.
(d) Some non-metals are ductile.
Answer: (c) Generally, metals are ductile.
In simple words: Most metals can be pulled into thin wires, but not absolutely all of them. Non-metals, however, cannot be made into wires.

Exam Tip: Understand the difference between "all" and "generally" when describing properties of elements, as there are often exceptions in chemistry.

Question 3. Fill in the blanks.
(a) Phosphorus is a very __________ non-metal.
(b) Metals are __________ conductors of heat and __________.
(c) Iron is __________ reactive than copper.
(d) Metals react with acids to produce __________ gas.
Answer:
(a) reactive
(b) good, electricity
(c) more
(d) hydrogen
In simple words: Phosphorus reacts easily, metals pass heat and electricity well, iron is more reactive than copper, and when metals touch acids, they often make hydrogen gas.

Exam Tip: Pay close attention to keywords like "reactive," "conductors," and "displace" when filling in blanks related to metal and non-metal properties.

Question 4. Mark 'T' if the statement is true and 'F' if it is false.
(a) Generally, non-metals react with acids.
(b) Sodium is a very reactive metal.
(c) Copper displaces zinc from zinc sulphate solution.
(d) Coal can be drawn into wires.
Answer:
(a) False
(b) True
(c) False
(d) False
In simple words: Non-metals don't usually react with acids, sodium is indeed very reactive, copper cannot push out zinc from its solution because it's less reactive, and coal breaks easily so it can't be made into wires.

Exam Tip: For true/false questions, recall the general properties and reactivity series of metals and non-metals to evaluate each statement accurately.

Question 5. Some properties are listed in the following Table. Distinguish between metals and non-metals on the basis of these properties.
Answer:

Exam Tip: When asked to distinguish between substances, creating a table is an effective way to present clear, side-by-side comparisons of their properties.

Question 6. Give reasons for the following.
(a) Aluminium foils are used to wrap food items.
(b) Immersion rods for heating liquids are made up of metallic substances.
(c) Copper cannot displace zinc from its salt solution.
(d) Sodium and potassium are stored in kerosene.
Answer:
(a) Aluminium is malleable, soft and does not react with food items, so it helps to wrap food items.
(b) Metals are good conductors of heat and electricity, so immersion rods are made up of metallic substances.
(c) Copper is less reactive than zinc, so it cannot displace zinc from its salt solution.
(d) Sodium and potassium are very reactive; they react with air and water. So they are kept in kerosene.
In simple words: Aluminium is flexible and safe for food, metals conduct heat well for heaters, copper is not strong enough to push zinc out, and sodium and potassium must be kept in oil because they react strongly with air and water.

Exam Tip: For "give reasons" questions, link the property (e.g., malleability, conductivity, reactivity) directly to the specific application or observation mentioned in the question.

Question 7. Can you store lemon pickle in an aluminium utensil? Explain.
Answer: No, we cannot keep lemon pickle in an aluminium utensil because aluminium is a metal and lemon is acidic. Acids react with metals to give hydrogen gas which would spoil the food and make it unsuitable for use.
In simple words: No, you cannot keep lemon pickle in an aluminium pot because the acid in the lemon would react with the aluminium metal, producing gas that spoils the food.

Exam Tip: Remember that acidic foods should not be stored in metal containers, especially reactive metals like aluminium, due to possible chemical reactions.

Question 8. Match the substances given in Column A with their uses given in Column B.

Exam Tip: When matching columns, carefully consider the unique properties of each substance that make it suitable for a specific use.

Question 9. What happens when
(a) Dilute sulphuric acid is poured on a copper plate?
(b) Iron nails are placed in copper sulphate solution?
Write word equations of the reactions involved.
Answer:
(a) When dilute sulphuric acid is poured on a copper plate, copper reacts with the acid to give copper sulphate and hydrogen gas.
Sulphuric acid + Copper \( \rightarrow \) Copper sulphate + Hydrogen
(b) When iron nails are placed in copper sulphate solution, a displacement reaction happens in which iron pushes out copper.
Copper sulphate + Iron \( \rightarrow \) Iron sulphate + Copper The blue colour turns into green.
In simple words: (a) Copper and sulphuric acid make copper sulphate and hydrogen gas. (b) Iron takes copper's place in copper sulphate solution, changing the blue solution to green as iron sulphate forms and copper metal appears.

Exam Tip: Always remember the reactivity series of metals to predict whether a displacement reaction will occur. More reactive metals displace less reactive ones.

Question 10. Saloni took a piece of burning charcoal and collected the gas evolved in a test tube.
(a) How will she find the nature of the gas?
(b) Write down word equations of all the reactions taking place in this process.
Answer:
(a) When charcoal is burnt, carbon dioxide gas is formed. This gas changes lime water to milky. It can also be checked by red and blue litmus. The solution of gas changes blue litmus to red, so it is acidic.
(b) Carbon + Oxygen \( \rightarrow \) Carbon dioxide
Carbon dioxide + Lime water \( \rightarrow \) Milky
In simple words: (a) She can test the gas by seeing if it turns lime water milky or changes blue litmus paper to red, which means it's an acidic gas. (b) When charcoal (carbon) burns, it combines with oxygen to make carbon dioxide. This carbon dioxide then reacts with lime water to turn it milky.

Exam Tip: Recall the common tests for gases, such as the lime water test for carbon dioxide and litmus paper tests for acidic or basic gases.

Question 11. One day Reeta went to a jeweller's shop with her mother. Her mother gave an old gold jewellery to the goldsmith to polish. Next day when they brought the jewellery back, they found that there was a slight loss in its weight. Can you suggest a reason for the loss in weight?
Answer: Gold is a metal which is washed in an acidic solution. Some gold dissolves in the acid to form an oxide. This causes the loss of gold in the form of gold oxide. In this process, a certain amount of gold is lost to the acidic solution.
In simple words: When the gold jewellery was polished, it was cleaned with an acidic liquid. A little bit of the gold dissolved into this acid, forming gold oxide, which caused the jewellery to lose some of its original weight.

Exam Tip: Be aware that even noble metals like gold can react with strong acids, leading to a loss of material, especially during processes like polishing.