Worksheets and lesson ideas to challenge students aged 11 to 16 to think hard about photosynthesis (GCSE and Key Stage 3)
Overview: photosynthesis is perhaps the most fundamental endothermic process on the planet, but it is often a difficult topic for students. Some of this confusion stems from the different ways we try to define what the process does – to create energy, to capture the sun’s energy, to make glucose. I find it helps to simply describe it as the process through which the plant produces its own food and therefore plants still need to respire. Stress the fact that the mass of a plant comes from the invisible carbon dioxide and without plants, our lives would be over.
Key concept: photosynthesis is the process by which plants use energy from the Sun to make their own food from carbon dioxide and water.
Misconception [scientific idea]: photosynthesis is the plant’s type of respiration [plants photosynthesise and respire]; plants get their food from the ground [plant’s produce their own food via photosynthesis – the mass mainly comes from carbon dioxide]; plants acquire food as they grow [plants produce their own food]; plants photosynthesise for humans [plants need to photosynthesise to make their own food – oxygen is a waste product] .
Some of the MIT graduates in the video below seem to struggle with the idea of a gas having a mass.
Where to start?
Ask student where sugar and starch come from. If you can get hold of a sugar beet/potato bring it to class. This video, involving the dehydration of sucrose, helps students make the link between carbon captured in plant sugars and carbon dioxide from the air. All living organisms are essentially walking, talking blocks of carbon. This demonstration must be carried out in a fume cupboard.
Uses of glucose from photosynthesis
GCSE worksheet imagining a world without plants: uses for glucose activity. Students consider how plants use glucose produced by photosynthesis. We think about how humans use plants and students write a paragraph describing what their life would be like without plants. The goal of this activity is for students to consider the importance of photosynthesis to both plants and humans. (PDF)
Function of photosynthesis
Key Stage 3 creative writing activity on the Green Child and photosynthesis. Students use their imagination to write a story about a Green Child that can photosynthesise. This approach can support student motivation and lead to deep thinking about the ideas of photosynthesis and respiration. (PDF)
Comparing photosynthesis with respiration
GCSE worksheet on respiration and photosynthesis. This simple activity asks students whether they understand the subtle but important differences between photosynthesis and respiration. Students discuss in pairs the question: Do plants respire? (PDF)
The leaf factory – photosynthesis and respiration
Key Stage 3 and GCSE activity looking at the relationship between respiration and photosynthesis.. Mitochondria and chloroplasts are compared to factories to help students understand the relationship between the products of photosynthesis and the reactants of respiration. This worksheet can also be used to help students evaluate the use of models to teach scientific processes. (PDF)
Limiting factors in photosynthesis
GCSE worksheet on limiting factors in photosynthesis. Liebig’s barrel is an excellent model to help students understand the concept of limiting factors in photosynthesis. Students should have already been introduced to limiting factors and photosynthesis before they meet this analogy model. Students identify the different features of the model and then complete the blank template to help identify analogous and non-analogous features. Image source. (PDF)
- What role did photosynthesis have in the evolution of multicellular organisms?
- What is the difference between rate and time?
- What is the endosymbiosis theory and why was it important in the evolution of plants?
- Give other examples of limiting factors in science