Daily Read / Plants and energy
Plants and energy · Use a labelled diagram together with the text to name what goes into and comes out of photosynthesis, explain why leaves look green, and check the claim that plants eat soil against evidence
How Do Plants Make Food? Photosynthesis in One Diagram
How do plants make food without eating? Use a labelled diagram to follow sunlight, water and carbon dioxide into sugar and oxygen, and test the idea that plants eat soil.
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A plant with no kitchen
A pumpkin vine can grow across a garden all summer, and nobody ever feeds it a meal. Where does its food come from? Kids Britannica gives a short answer: photosynthesis is the process in which green plants use sunlight to make their own food.
Kids Britannica lists four things a plant needs for this job: sunlight, chlorophyll, water and carbon dioxide gas. Chlorophyll is a substance found in all green plants, especially in the leaves. The next sections follow each ingredient through the diagram.[1]
What goes in
Look at the big box of the diagram. Three arrows point toward the leaves. The first is sunlight, which gives the energy. The second is carbon dioxide. NASA Climate Kids explains that carbon dioxide is called CO2 because it has two oxygen atoms attached to one carbon atom, and that plants absorb it from the air.
The third arrow is water. Kids Britannica says plants take in water from the soil, and they take in carbon dioxide from the air. National Geographic Education says the same thing in a short phrase: plants take in carbon dioxide and water from the air and soil. Notice that one ingredient comes from above the ground and one from below it.[3]
Why leaves are green
Now look at the small box on the right. National Geographic Education explains that photosynthesis happens in small parts of plant cells called chloroplasts. The light-catching chlorophyll is inside them.
Chlorophyll absorbs blue and red light and reflects green light. That reflected green light is why plants look green to us. Sunlight is a mix of colours, and the plant uses some of them as its energy supply.[2]
What comes out
Kids Britannica says chlorophyll absorbs light energy, and the plant uses that energy to change water and carbon dioxide into oxygen and sugars. The plant uses some of the sugars and stores the rest. The oxygen is released into the air.
National Geographic Education adds that plants store energy in sugar molecules. Animals that eat plants get that energy from them, and animals that eat those animals get it second-hand. Kids Britannica also says humans and animals need the oxygen that photosynthesis produces, and that certain bacteria and algae photosynthesize too.[1]
Where does a tree's weight come from?
Many people guess that a growing plant eats the soil. In the 1640s, Jan Baptist van Helmont tested the idea with a willow tree. A chapter published by Open Book Publishers reports that the tree gained 164 pounds, about 74 kilograms, while the soil lost only 2 ounces, about 60 grams.
The same chapter says that most of a tree's dry mass comes from carbon dioxide in the air, about 95 per cent, and that scientists have traced the carbon in wood back to atmospheric carbon dioxide. So the plant's 'food' is built from air and water, with energy from the sun. Soil still matters, because roots take in water from it, but the sugar itself is made inside the plant.[4]
Fast lesson
Use these checks before you answer the practice questions.
Children often list sunlight as food. Ask: what is the plant made from, and what powers the change? Water and carbon dioxide are ingredients; sunlight is the energy.
The diagram is a simplified schematic. Real chloroplasts and cells are far too small to see without a microscope. Say 'the diagram shows' rather than 'a leaf looks like this'.
Compare 74 kilograms with 60 grams out loud. Large and small numbers make the argument against 'plants eat soil' concrete, and van Helmont's result is one test, not the whole story.
The 95 per cent figure comes from one book chapter. Practise saying 'this source says' and look for a second source before treating a number as settled.
Common mistakes
Why this fails: Plants make sugar in their leaves from sunlight, water and carbon dioxide. Roots take in water from the soil, but the soil does not become the plant's food.
Why this fails: It is the other way round: carbon dioxide goes in and oxygen comes out.
Why this fails: Sunlight supplies the energy. The sugar is made from water and carbon dioxide.
Word Lab
Use the meaning, hear the word, then try it in your own sentence.
photosynthesis
nounthe process in which green plants use sunlight to make their own food
Photosynthesis happens mostly in the leaves.
chlorophyll
nouna green substance in plants that absorbs light
Chlorophyll reflects green light.
chloroplast
nouna tiny part of a plant cell where photosynthesis happens
Chlorophyll is inside each chloroplast.
carbon dioxide
nouna gas in the air that plants take in; written CO2
Plants absorb carbon dioxide from the air.
oxygen
nouna gas that plants release and that people and animals need
The leaves release oxygen into the air.
sugar
nounthe food a plant makes, which stores energy
The plant uses some sugar and stores the rest.
energy
nounthe ability to make things happen; sunlight supplies it
Sunlight gives the plant energy.
absorb
verbto take in
Chlorophyll absorbs blue and red light.
reflect
verbto bounce back
Leaves reflect green light to our eyes.
ingredient
nounone of the things needed to make something
Water is one ingredient of photosynthesis.
release
verbto let go or send out
Plants release oxygen into the air.
soil
nounthe loose top layer of earth where roots grow
Roots take in water from the soil.
Check your understanding
Choose an answer, explain your choice, and then check. Hints and retries are welcome.
Try the questions here. Public practice does not save a learning record.
Support · Find it in the text
Support · Find it in the text practice
Each answer is stated in the article. Point to the sentence.
1. What four things does Kids Britannica say a plant needs for photosynthesis?
2. Where do plants get their water, and where do they get carbon dioxide?
3. What are chloroplasts?
4. Which colours of light does chlorophyll absorb, and which does it reflect?
5. What does the plant do with the sugars it makes?
6. What does CO2 stand for, according to NASA Climate Kids?
Apply · Process and cause
Apply · Process and cause practice
Use first, then, because or so to explain how a plant makes food.
7. Finish the sentence: Leaves look green, because …
8. Finish the sentence: A plant in a dark closet cannot photosynthesize well, because …
9. Finish the sentence: The plant releases oxygen, so …
10. Put in order: sugar and oxygen come out, light is absorbed by chlorophyll, water and carbon dioxide are changed.
11. Why did van Helmont's willow result surprise people who thought plants eat soil?
12. Finish the sentence: Green plants make their own food, because …
Reason · New situations
Reason · New situations practice
Use what you learned to reason about new situations.
13. Is carbon dioxide an ingredient or a product of photosynthesis?
- Ingredient
- Product
14. Is oxygen an ingredient or a product of photosynthesis?
- Ingredient
- Product
15. Is sunlight an ingredient, a product or the energy source?
- Ingredient only
- Product
- Energy source
16. A pot of water-loving plants is moved from a bright window to a dim corner. Predict what happens to their sugar-making and say why.
17. A child says, 'Soil is a plant's food, like a bowl of soup.' What would you say?
Practice answer key
- 1. Sunlight, chlorophyll, water and carbon dioxide.
See 'A plant with no kitchen'. - 2. Water from the soil; carbon dioxide from the air.
See 'What goes in'. - 3. Small parts of plant cells where photosynthesis happens.
See 'Why leaves are green'. - 4. It absorbs blue and red and reflects green.
See 'Why leaves are green'. - 5. It uses some and stores the rest.
See 'What comes out'. - 6. Carbon dioxide: two oxygen atoms attached to one carbon atom.
See 'What goes in'. - 7. … chlorophyll reflects green light.
Green is the colour that is not absorbed. - 8. … sunlight supplies the energy for the process.
Water and carbon dioxide alone do not give the plant energy. - 9. … animals, including people, can breathe it in.
Kids Britannica says humans and animals need the oxygen that photosynthesis produces. - 10. Light is absorbed by chlorophyll; water and carbon dioxide are changed; sugar and oxygen come out.
The plant needs the light energy before it can change the ingredients. - 11. The tree gained about 74 kilograms but the soil lost only about 60 grams.
If the tree had eaten the soil, the soil would have lost far more weight. - 12. … they make sugar inside themselves from sunlight, water and carbon dioxide.
They do not need to eat other living things. - 13. Ingredient
Plants take it in from the air. - 14. Product
The plant releases oxygen into the air. - 15. Energy source
Sunlight supplies the energy, the plant does not 'eat' it. - 16. They make less sugar, because there is less light energy.
The same water and air are there, but the energy supply is smaller. - 17. Plants make their own food inside the leaves from sunlight, water and carbon dioxide; roots take up water from the soil.
The willow evidence shows soil lost very little.
Related skills
Put it in your own words
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Check your own explanation
This is self-review, not automatic marking.
Compare with a model response
A green plant makes its own food by photosynthesis. First, the roots take in water from the soil and the leaves take in carbon dioxide from the air. Chlorophyll in the chloroplasts absorbs sunlight, which gives the plant energy. Then the plant changes the water and carbon dioxide into sugar and oxygen. It uses some of the sugar and stores the rest, and it releases the oxygen into the air. Some people think plants eat soil, but a willow tree gained about 74 kilograms while its soil lost only about 60 grams, so the soil cannot be the main source. The diagram is simplified, so real leaves are more complicated.
Sources and revision notes
Source check: 2026-11-12. Grade guidance is an editorial suggestion, not a standardised reading score.
- Kids Britannica — photosynthesis
- National Geographic Education — Photosynthesis
- NASA Science for Kids — What Is the Carbon Cycle?
- Open Book Publishers — From Air to Arbor (chapter 35)
What changed in this edition?
The definition of photosynthesis, the four needs (sunlight, chlorophyll, water, carbon dioxide), the uptake of water from the soil and carbon dioxide from the air, the change into oxygen and sugars, the use and storage of sugars, and the point that humans and animals need the oxygen come from Kids Britannica. The chloroplasts, the absorption of blue and red light and reflection of green, and the energy passing to animals that eat plants come from National Geographic Education. The meaning of CO2 and the point that plants absorb carbon dioxide come from NASA Science for Kids. The willow-tree figures, the roughly 95 per cent share of dry mass from atmospheric carbon dioxide and the tracing of wood carbon to the air come from the Open Book Publishers chapter; that chapter is one source, so treat the percentage as that source's statement. The pumpkin-vine opening, the window test, the closet and dim-corner examples, the diagram shapes and the home activity are original illustrations or reasoning. Report errors through Sources and corrections.