CIE iGCSE Co-Ordinated Science B6.1 Photosynthesis Exam Style Questions Paper 1
Question
Which process removes carbon dioxide from the atmosphere?
A. combustion
B. photosynthesis
C. respiration
D. transpiration
▶️Answer/Explanation
Answer: B
Explanation: Photosynthesis is the process by which plants remove carbon dioxide from the atmosphere and convert it into glucose and oxygen using sunlight.
Question
Four test-tubes were set up as shown. Which test-tube will contain the most dissolved oxygen after 24 hours?
▶️Answer/Explanation
Answer: A
Explanation: The aquatic plant will produce oxygen through photosynthesis in the presence of light, leading to the highest concentration of dissolved oxygen in test-tube A.
Question
The diagram shows an experiment to investigate photosynthesis. When leaves photosynthesise, they store some carbohydrates as starch.
Potassium hydroxide absorbs carbon dioxide.
After standing in sunlight for 10 hours, leaf L contained no starch but leaf M contained a lot of starch.
What does this show?
A. A leaf cannot make starch in a sealed flask.
B. A leaf cannot make starch without carbon dioxide.
C. A leaf cannot make starch without light.
D. A leaf cannot make starch without oxygen.
▶️Answer/Explanation
Answer: B. A leaf cannot make starch without carbon dioxide.
Explanation: Potassium hydroxide absorbs carbon dioxide, so leaf L was deprived of CO₂ and could not photosynthesize to produce starch. Leaf M had access to CO₂ and was able to produce starch.
Question
Which ion is important for chlorophyll production in plants?
A calcium
B iron
C magnesium
D nitrate
▶️Answer/Explanation
Ans :C
Question
The diagram shows an investigation into factors affecting photosynthesis.
The tubes are left for 24 hours after which the leaves are tested with iodine solution.
How many of these leaves turn blue-black when tested with iodine solution?
A 1 B 2 C 3 D 4
▶️Answer/Explanation
Ans :A
Question
A student places a plant in the dark for 24 hours.
Aluminium foil is then placed around one leaf.
A second leaf is sealed in a bag with soda lime to remove carbon dioxide.
A third leaf is then sealed in a bag with iron filings to remove oxygen.
The plant is then left in the light for a further 24 hours.
The diagram shows the experiment.
Which leaves would turn blue-black when tested with iodine solution?
A X only B X and Y C Y and Z D Z only
▶️Answer/Explanation
Ans :A
Question
A plant with variegated leaves is destarched. A strip of black paper is attached to both sides of a leaf and the plant is placed in the light for 24 hours.
The leaf is then tested for starch.
Which areas of the leaf stain blue-black with iodine?
(A) 1 and 4
(B) 1 only
(C) 2 and 3
(D) 2 only
▶️Answer/Explanation
Ans: D
Question
Which row is correct for photosynthesis?
▶️Answer/Explanation
Ans : B
Question
Why are nitrate ions necessary for plant growth?
A They are essential for producing starch.
B They are found in the chloroplasts.
C They are part of the cell sap.
D They are used in making amino acids.
▶️Answer/Explanation
Ans : D
Question
The diagram shows a leaf, still attached to a plant, with both green and white areas that have been partly covered with black paper.
The leaf is left in bright light for six hours and then tested for starch.
Which area of the leaf turns blue-black after the starch test?
▶️Answer/Explanation
Ans : B
Question
Which two arrows represent photosynthesis?
(A) 1 and 3 (B) 1 and 4 (C) 2 and 3 (D) 2 and 4
▶️Answer/Explanation
Ans : B
Question
Plants require various ions to manufacture other molecules.
Which row shows the molecules that plants make from magnesium ions and nitrate ions?
▶️Answer/Explanation
Ans: B
Question
Which conditions will result in the highest rate of photosynthesis?
▶️Answer/Explanation
Ans : A
Question
Which word is missing from the word equation for photosynthesis?
carbon dioxide + ………………… → glucose + oxygen
(A) carbohydrate
(B) chlorophyll
(C) light
(D) water
▶Answer/Explanation
Ans : D
Question
Which statements about chemical changes are correct?
1. The separation of petroleum into gasoline, naphtha and diesel is a chemical change.
2. The separation of water into hydrogen and oxygen is a chemical change.
3. In a chemical change, a new substance is always formed.
4. In a chemical change, heat is always released.
(A) 1 and 2 (B) 1 and 4 (C) 2 and 3 (D) 3 and 4
▶️Answer/Explanation
Ans: C
Solution:
Let’s analyze each statement:
- The separation of petroleum into gasoline, naphtha, and diesel is a chemical change.
- Incorrect. This is a physical change (fractional distillation), as no new substances are formed.
- The separation of water into hydrogen and oxygen is a chemical change.
- Correct. This is electrolysis, which breaks water into hydrogen and oxygen (new substances are formed).
- In a chemical change, a new substance is always formed.
- Correct. A chemical change involves the formation of new substances with different properties.
- In a chemical change, heat is always released.
- Incorrect. Heat may be released (exothermic) or absorbed (endothermic) during a chemical change.
Correct Answer:
(C) 2 and 3
- Statement 2 (The separation of water into hydrogen and oxygen is a chemical change) and Statement 3 (In a chemical change, a new substance is always formed) are correct.
Question
Which process removes carbon dioxide from the atmosphere?
(A) combustion
(B) decomposition
(C) photosynthesis
(D) respiration
▶️Answer/Explanation
Ans: C
Solution:
The process that removes carbon dioxide from the atmosphere is photosynthesis.
- Photosynthesis is the process by which plants, algae, and some bacteria use sunlight to convert carbon dioxide and water into glucose and oxygen. This removes carbon dioxide from the atmosphere.
- The other options:
- Combustion (A) releases carbon dioxide into the atmosphere.
- Decomposition (B) releases carbon dioxide as organic matter breaks down.
- Respiration (D) releases carbon dioxide as a byproduct of energy production in living organisms.
Correct Answer:
(C) photosynthesis
Question
The rate of photosynthesis of an aquatic plant is measured by counting the number of bubbles of oxygen produced every minute, as shown. The rate is measured at different light intensities.
Which two variables need to be kept constant?
(A) size of plant and temperature of the water
(B) light intensity and size of the boiling tube
(C) size of plant and size of the boiling tube
(D) temperature of the water and light intensity
▶️Answer/Explanation
Ans: A
Question
Which graph shows the effect of increasing light intensity on the rate of photosynthesis?
▶️Answer/Explanation
Answer: C
Explanation: The rate of photosynthesis increases with light intensity up to a certain point, after which it plateaus due to other limiting factors such as carbon dioxide concentration or temperature. Graph C correctly shows this relationship, where the rate of photosynthesis increases linearly with light intensity and then levels off.
Question
Which are the products of photosynthesis in a green plant?
A. carbon dioxide and water
B. glucose and carbon dioxide
C. oxygen and glucose
D. oxygen and water
▶️Answer/Explanation
Answer: C. oxygen and glucose
Explanation: Photosynthesis in green plants produces glucose (a form of sugar) and oxygen as byproducts. The overall equation for photosynthesis is: carbon dioxide + water → glucose + oxygen, in the presence of light and chlorophyll.
Question
Which conditions will result in the highest rate of photosynthesis?
| Light intensity | Carbon dioxide concentration | |
|---|---|---|
| A | high | high |
| B | high | low |
| C | low | high |
| D | low | low |
▶️Answer/Explanation
Answer: A) high light intensity and high carbon dioxide concentration
Explanation: Photosynthesis is most efficient when both light intensity and carbon dioxide concentration are high. Light is necessary for the light-dependent reactions, and carbon dioxide is a reactant in the Calvin cycle. Therefore, both factors must be optimal for the highest rate of photosynthesis.
Question
Which chemical element is present in chlorophyll?
A. calcium
B. iron
C. magnesium
D. sodium
▶️Answer/Explanation
Answer: C. magnesium
Explanation: Chlorophyll is the green pigment in plants that is essential for photosynthesis. It contains magnesium at its core, which is crucial for capturing light energy.
Question
A farmer observes that his field of grass is not looking as green as it should be. Which substance is likely to be in short supply?
A. carbon dioxide in the air
B. magnesium in the soil
C. nitrogen in the air
D. water in the soil
▶️Answer/Explanation
Answer: B. magnesium in the soil
Explanation: Magnesium is a key component of chlorophyll, the green pigment in plants. A deficiency in magnesium would lead to chlorosis, causing the grass to appear less green.
Question
The diagram shows a variegated leaf.
Which requirement for photosynthesis can be tested using this leaf but not a completely green leaf?
A. carbon dioxide
B. chlorophyll
C. light
D. water
▶️Answer/Explanation
Answer: B. chlorophyll
Explanation: A variegated leaf has both green (chlorophyll-containing) and non-green (chlorophyll-lacking) areas. By comparing the green and non-green areas, you can test the requirement for chlorophyll in photosynthesis.
Question
An investigation was carried out to show that carbon dioxide was necessary for photosynthesis to occur in a plant. Which conditions should the plant be kept in as a suitable control for this experiment?
A. Clear container, with lots of carbon dioxide
B. Clear container, without any carbon dioxide
C. Black container, with lots of carbon dioxide
D. Black container, without any carbon dioxide
▶️Answer/Explanation
Answer: B. Clear container, without any carbon dioxide
Explanation: The control experiment should have all conditions the same as the experimental setup except for the absence of carbon dioxide. This allows for a comparison to determine the effect of carbon dioxide on photosynthesis.
Question
What is the word equation for photosynthesis?
A carbon dioxide + glucose → oxygen + water
B carbon dioxide + water → oxygen + glucose
C oxygen + glucose → carbon dioxide + water
D oxygen + water → carbon dioxide + glucose
▶️Answer/Explanation
Answer: B
Explanation: The correct word equation for photosynthesis is carbon dioxide + water → oxygen + glucose, in the presence of light and chlorophyll.
Question
Plants make sugars from water and carbon dioxide. From where do they get the carbon dioxide?
A. rain soaking into the leaves
B. the air
C. the soil through the roots
D. they make it in photosynthesis
▶️Answer/Explanation
Answer: B
Explanation: Plants obtain carbon dioxide from the air through tiny openings called stomata on their leaves. This carbon dioxide is used in the process of photosynthesis to produce sugars.