Plants Build Themselves from Air and Water

Science · Organisms & Life Processes · ages 10-11

Name ______________________ Date ____________

Besides carbon dioxide, what else does a plant use to make its food?
- Rocks
- Water
- Sand
What gas do plants take in from the air to make food?
- Carbon dioxide
- Oxygen
- Nitrogen
True or false: most of a plant's mass comes from the soil.
Circle one: True False
A scientist grows a plant in a pot for a year, then weighs the soil again. What most likely happens to the soil's weight?
- It barely changes
- It doubles
- It disappears completely
Look at the graph showing what a plant's mass is made of. Which material makes up the smallest share?
- Air
- Water
- Soil
A pot of soil weighed 2000 grams before planting. After a year of plant growth, it weighed 1990 grams. How many grams did the soil lose?
Answer: ______________
If a tree gains 50 kg of new wood in a year, where did most of that new material most likely come from?
- Minerals dissolved from the soil
- Sunlight turning directly into wood
- Carbon dioxide from the air and water from the roots
Maria says plants must be eating soil to grow bigger. What evidence would prove her wrong?
- The plant's leaves turn yellow
- Soil mass stays nearly the same while the plant grows a lot
- The pot needs more water each week

Answer key

For grown-ups. Fold this page away before handing over the rest.

Water · Photosynthesis needs both carbon dioxide from the air and water from the roots.
Carbon dioxide · Plants pull carbon dioxide from the air and combine it with water to make food.
False · Most of a plant's mass comes from air and water, not from soil.
It barely changes · The soil loses very little mass, even though the plant grows much bigger.
Soil · Soil only supplies a small share of minerals; air and water make up almost all the rest.
10 · 2000 minus 1990 is 10 grams, a tiny amount compared to how much the plant grew.
Carbon dioxide from the air and water from the roots · Sunlight provides energy, but the actual building material is carbon dioxide and water, turned into sugar and then into wood.
Soil mass stays nearly the same while the plant grows a lot · If the plant were eating the soil, the soil's mass would drop a lot. It barely changes, so the plant's new material must come from somewhere else.