Home / iGCSE Chemistry (0620) Core:10.1 Water: Exam Style Questions Paper 1

iGCSE Chemistry (0620) Core:10.1 Water: Exam Style Questions Paper 1

iGCSE Chemistry (0620) Core Paper 1 - All Chapters
Question

Which word equation describes photosynthesis?

A) carbon dioxide + water → glucose + oxygen
B) glucose + water → carbon dioxide + oxygen
C) carbon dioxide + oxygen → glucose + water
D) glucose + oxygen → carbon dioxide + water

▶️ Answer/Explanation
Solution

Ans: A

Photosynthesis is the process by which plants use sunlight to convert carbon dioxide and water into glucose and oxygen. The correct word equation is: carbon dioxide + water → glucose + oxygen. Option B describes respiration, while options C and D are incorrect combinations. Remember that photosynthesis takes in carbon dioxide and water, and produces glucose and oxygen as byproducts.

Question

Which substances in water from natural sources are beneficial to aquatic animals?

  1. metal compounds
  2. plastics
  3. phosphates
  4. dissolved oxygen

A) 1 and 2
B) 1 and 4
C) 2 and 3
D) 3 and 4

▶️ Answer/Explanation
Solution

Ans: B

Let’s analyze each substance:

  1. Metal compounds: Some metal compounds in trace amounts (like calcium and magnesium) are essential for aquatic life.
  2. Plastics: Harmful to aquatic animals as they can cause entanglement or be mistaken for food.
  3. Phosphates: While necessary in small amounts, excess phosphates can lead to eutrophication and harm aquatic ecosystems.
  4. Dissolved oxygen: Absolutely essential for aquatic animals to breathe.

Therefore, the beneficial substances are metal compounds (1) and dissolved oxygen (4), making option B correct.

Question

Which pollutants found in river water lead to deoxygenation?

  1. nitrates
  2. harmful microbes
  3. metal compounds
  4. phosphates

A) 1 and 2
B) 1 and 4
C) 2 and 3
D) 3 and 4

▶️ Answer/Explanation
Solution

Ans: B

Nitrates (1) and phosphates (4) are nutrients that cause excessive growth of algae in water bodies. When these algae die and decompose, the process consumes oxygen from the water, leading to deoxygenation. This phenomenon is called eutrophication.

Harmful microbes (2) may cause diseases but don’t directly reduce oxygen levels. Metal compounds (3) can be toxic but don’t typically cause deoxygenation. Therefore, the correct combination is 1 and 4, which corresponds to option B.

Question

 Which statement shows that a liquid is pure water?
A It boils at $100^{\circ} \mathrm{C}$.

B It has a pH value of 7 .

C It turns blue cobalt(II) chloride pink.

D It turns white copper(II) sulfate blue.

▶️Answer/Explanation

Ans:A

If a liquid boils at exactly 100 degrees Celsius under standard atmospheric pressure (1 atmosphere or 101.3 kPa), then it is pure water. Boiling point is a characteristic property of a substance, and for water at sea level, the boiling point is 100 degrees Celsius (212 degrees Fahrenheit).

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