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

Grade 7 Science Worksheet

Circle the best answer.

1. 1.

   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 speeds up, because the leaf keeps its water
   • It slows, because less oxygen gets into the leaf
2. 2.

   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

3. 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.

4. 3.

   Jun’s class tested a water plant under a lamp. What did the class change on purpose?

   • The number of bubbles each minute
   • The kind of water plant
   • The distance from the lamp
   • The amount of water in the jar
5. 4.

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

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

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

   • More light, with the lamp closer, means faster photosynthesis
   • The plant gives off the most gas far from the lamp
   • The distance made no difference to the plant
   • Closer to the lamp, the plant takes in more oxygen from the air
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 sunlight, which turns into plant material
   • From water alone, which turns into stems and leaves
   • From carbon dioxide in the air, built into sugar
   • From the soil, which the roots take in

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

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

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

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

    Use the picture in question 8.

    • The sugar arrow to the rest of the plant
    • The water arrow from the roots and stem
    • The carbon dioxide arrow from the air
    • The light arrow from the Sun
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 gone, since light leaves the leaf unchanged
    • It is stored as chemical energy in the sugar
    • It is stored in the oxygen given off
    • It has turned into the sugar’s matter