Photosynthesis: how plants make food from light, water and air

Grade 7 Science Worksheet

Circle the best answer.

1. 1.

   Ari moves a bean plant into a dark closet for two days. What happens to the sugar its leaves make?

   • The same amount, because the water brings the energy
   • The same amount, because the plant still gets its food from the soil
   • Less sugar is made, because light energy powers photosynthesis
   • More sugar, because the plant has more time to rest
2. 2.

   On a hot afternoon, Bo’s sunflower closes its stomata to save water. What happens to photosynthesis?

   • It slows, because less carbon dioxide gets into the leaf
   • It stays the same, because the roots supply the carbon it needs
   • It slows, because less oxygen gets into the leaf
   • It speeds up, because the leaf keeps its water
3. 3.

   Esme’s potted plant gets no water for a week, while its light and air stay the same. Why does it make less sugar?

   • Without water, the leaf cannot take in oxygen
   • Water is one of the inputs that is built into sugar
   • Water is the plant’s food, and it has run out
   • Without water, food from the soil cannot reach the leaf

4. Read this first

   Use this

   Investigation card (model data). Question: does the distance from a lamp change how fast a water plant gives off bubbles? Changed: distance from an LED desk lamp. Measured: bubbles counted in one minute. Kept the same: plant, jar, water, lamp, counting time. Results table: Distance (cm) | Bubbles per minute: 10 | 24; 20 | 13; 30 | 6.

5. 4.

   Kira’s class tested a water plant under a lamp. What gas do the bubbles show?

   • Air the plant took in from the water
   • Oxygen given off as the plant makes sugar
   • Carbon dioxide given off as the plant makes sugar
   • Steam made by the lamp warming the water
6. 5.

   Luz’s class tested a water plant under a lamp. Which conclusion fits the data?

   • Closer to the lamp, the plant takes in more oxygen from the air
   • The plant gives off the most gas far from the lamp
   • The distance made no difference to the plant
   • More light, with the lamp closer, means faster photosynthesis
7. 6.

   Milo plants a bean seed, and it grows into a plant many times heavier. Where does most of the new mass come from?

   • From water alone, which turns into stems and leaves
   • From the soil, which the roots take in
   • From sunlight, which turns into plant material
   • From carbon dioxide in the air, built into sugar

8. Data card (model data)

   Dry soil in the pot, start 2,000 g, after eight weeks 1,995 g. Sunflower: start 10 g, after eight weeks 300 g.

9. 7.

   Noah’s class grew a sunflower in a pot for eight weeks and weighed the dry soil before and after. What does the soil data show?

   • The plant’s new mass came from the soil
   • The plant gave some of its mass to the soil
   • The light itself turned into most of the plant’s new mass
   • Most of the plant’s new mass did not come from the soil
11. 8.

    Pia reads that sugar is built partly from carbon. Which input gives the plant the carbon in its sugar?

    • Minerals in the soil
    • Carbon dioxide from the air
    • Water from the roots
    • Light energy from the Sun
12. 9.

    Ren sorts the arrows on a leaf diagram. Which arrow carries energy but no matter?

    Use the picture in question 8.

    • The light arrow from the Sun
    • The sugar arrow to the rest of the plant
    • The water arrow from the roots and stem
    • The carbon dioxide arrow from the air
13. 10.

    Tala asks where the light energy goes after a leaf makes sugar. Which answer is right?

    Use the picture in question 8.

    • It is stored in the oxygen given off
    • It is stored as chemical energy in the sugar
    • It is gone, since light leaves the leaf unchanged
    • It has turned into the sugar’s matter