ScienceGrade 7ages 12–13
🍃 Plant and light
A plant makes its food using light — most of its body is built from carbon dioxide in the air and water, not from soil, which mainly supplies water and minerals rather than being "eaten" as a meal.
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Download on the App StoreWhat your child learns
- Once, a pot of soil with a small seedling was weighed, and then years passed until a tree grew.
- The tree gained tens of kilograms, but the soil in the pot barely lost any weight.
- So the tree's body did not come from the soil. Most of it was built from carbon dioxide in the air, and from water.
- Light is the energy that makes that building possible, and the soil supplies water and minerals.
The mistake most kids make here
A plant eats soil as a meal, and light only warms the leaves.
Try one question
A green plant makes food mainly using…
Makes using
- a dirt meal like a sandwich
- light
- only the pot's colour
Answer
light — Yes. Light supplies the energy without which the materials cannot be joined into food.
How Maya teaches it
Your child tells Maya what they did in class. She teaches this topic at her desk, asks questions with tappable answers, and when the answer is wrong she explains why that answer was tempting instead of saying “try again”. She remembers what did not land and comes back to it.
Your child has it when they can: Say where the plant makes food, and what soil does give.
How to help at home
Since plants grow out of soil and seem to depend on it, it's a natural guess that soil must be their food, the way dirt is nourishment. The fix is a surprising real experiment: weighing the soil before and after a tree grows in it for years.
Tonight, tell your child about this experiment: a small seedling is planted in a weighed pot of soil, and years later, after growing into a full tree weighing many kilograms, the soil in the pot has barely lost any weight at all.
If your child assumes the tree's mass must have come from the soil, ask where else it could have come from if the soil barely changed. The answer is the air (carbon dioxide) and water, built into food using the energy from light.
A good sign they've got it: they can say a plant makes food mainly using light, building its body from air and water, while soil mostly supplies water and minerals rather than being eaten as food.
Questions parents ask
- Why does my child think a plant eats soil?
- Because plants grow rooted in soil and clearly depend on it, it's a reasonable first guess that soil must be their food source, much like dirt is nourishment for them.
- If not from soil, where does a tree's mass actually come from?
- Mostly from carbon dioxide in the air and from water — a plant uses the energy in light to build its own food (and body) from these, which is why a tree can grow to weigh far more than the soil around it loses.
- What does soil actually give a plant, then?
- Soil mainly supplies water and minerals — important, but a small part of what ends up making up the plant's actual mass.
- How does Maya teach this differently from a worksheet?
- Maya asks what a green plant mainly uses to make food and offers "a dirt meal" as a wrong option, so a child has to reason from evidence rather than assume soil is the plant's food.
No card needed. The first lesson is free.
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Sources: Next Generation Science Standards