Photosynthesis

Science Worksheet — Ages 11–13

Read each question carefully, then write your answers in the spaces provided.

1. Fill in the Blank

Complete the word equation for photosynthesis:

$$\text{\_\_\_\_\_\_\_\_\_\_} + \text{Water} \xrightarrow{\text{Light Energy}} \text{Glucose} + \text{\_\_\_\_\_\_\_\_\_\_}$$

2. Fill in the Blank

Photosynthesis takes place in the \_\_\_\_\_\_\_\_\_\_ of plant cells. This structure contains a green pigment called \_\_\_\_\_\_\_\_\_\_, which absorbs light energy.

3. Multiple Choice

Which part of the plant is the primary site of photosynthesis?

• A) Root


• B) Stem


• C) Leaf


• D) Flower

4. Multiple Choice

Which of the following conditions would most decrease the rate of photosynthesis in a healthy plant?

• A) Increasing the amount of water


• B) Moving the plant to a dark cupboard


• C) Raising the temperature from 15 °C to 25 °C


• D) Increasing the concentration of carbon dioxide

5. True or False

Write True or False next to each statement.

6. Short Answer

Explain why a plant kept in the dark for several days would eventually turn yellow and die. Use the words chlorophyll, glucose, and energy in your answer.

> \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
>
> \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

7. Word Problem

A scientist measures that a single leaf produces 18 ml of oxygen in one hour under bright light. She then moves the plant to a shaded area where it produces only one-third of that amount per hour.

• (a) How many ml of oxygen does the leaf produce per hour in the shade?


• (b) How many ml of oxygen would the leaf produce in 4 hours in the shade?

8. 🌟 Challenge Question

A student sets up an experiment with two identical potted plants — Plant A and Plant B. Both are placed in sunlight and given the same amount of water. However, Plant A is given air with normal levels of carbon dioxide, while Plant B is sealed in a container with no carbon dioxide.

After two weeks, Plant B has barely grown, while Plant A has grown noticeably.

• (a) Explain, using your knowledge of photosynthesis, why Plant B failed to grow.


• (b) Predict what would eventually happen to Plant B if the experiment continued for several more weeks. Give a reason for your prediction.

Answer Key

1. Fill in the Blank

$$\textbf{Carbon Dioxide} + \text{Water} \xrightarrow{\text{Light Energy}} \text{Glucose} + \textbf{Oxygen}$$

2. Fill in the Blank

Photosynthesis takes place in the chloroplast of plant cells. This structure contains a green pigment called chlorophyll, which absorbs light energy.

3. Multiple Choice

✅ C) Leaf
The leaf has a large surface area, many chloroplasts, and tiny pores (stomata) for gas exchange — making it the main site of photosynthesis.

4. Multiple Choice

✅ B) Moving the plant to a dark cupboard
Light is an essential requirement for photosynthesis. Without it, the reaction cannot occur. Options C and D would generally increase the rate; option A alone would not dramatically reduce it.

5. True or False

6. Short Answer

Accept answers that include the following key points:

Without light, the plant cannot produce chlorophyll (or existing chlorophyll breaks down), so it loses its green colour and turns yellow. With no light, photosynthesis stops and the plant cannot make glucose. Without glucose, the plant has no source of energy for growth and life processes, so it will eventually die.

7. Word Problem

• (a) 18 ÷ 3 = 6 ml of oxygen per hour in the shade


• (b) 6 × 4 = 24 ml of oxygen in 4 hours in the shade

8. 🌟 Challenge Question

(a) Carbon dioxide is one of the raw materials (reactants) needed for photosynthesis. Without it, Plant B cannot carry out photosynthesis and therefore cannot produce glucose. Without glucose, the plant has no energy or building materials for growth, which is why Plant B barely grew.

(b) Plant B would eventually wilt and die. Without photosynthesis, it cannot produce glucose to fuel respiration or to build new cells. It would use up any remaining stored glucose and starch, and once those reserves are exhausted, it would no longer be able to carry out essential life processes.

© Printable Science Worksheet — Photosynthesis | Ages 11–13