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

Grade 7 Science Worksheet - Challenge Me

Circle the best answer.

2. 1.

   Ari’s friend says plants get their food from the soil, so soil is plant food. Which response is best?

   • Agree: the roots pull the plant’s food out of the soil for it
   • Agree: fertilizer is the food that plants live on
   • Disagree: plants live on water and nothing else
   • Disagree: leaves make their sugar from carbon dioxide and water
3. 2.

   Esme’s friend says sunlight is a plant’s food. Which response is best?

   Use the picture in question 1.

   • Disagree: soil is the plant’s real food
   • Disagree: light gives energy; the food is sugar the leaf makes
   • Agree: plants grow by turning light into wood
   • Agree: leaves soak up light and store it inside as plant matter

4. Read this first

   Read-about history card

   In the 1600s Jan Baptist van Helmont grew a willow in a pot for five years, adding only water. The tree gained about 164 pounds; the dry soil lost only about 2 ounces.

5. 3.

   Jun reads about van Helmont’s willow. He decided the tree’s new mass came from water. What did he miss?

   • Nothing: water is where plant mass comes from
   • The mass came from the sunlight, which he left unweighed
   • Much of the mass came from carbon dioxide in the air
   • The mass really came from the soil

6. Investigation card (model data)

   Two matching water plants in sealed jars of water, the same size and temperature. Bubbles counted in 10 minutes: under an LED lamp, 40; in the dark, 0.

7. 4.

   Luz’s class compared two water plants in sealed jars, one under a lamp and one in the dark. Which conclusion is strongest?

   • The dark plant kept its bubbles for later
   • Light is needed for the plant to give off oxygen
   • The lamp plant took in oxygen from the jar
   • Light turned into the gas in the bubbles

8. Use this

   Leaf arrow diagram, not to scale. Boxes: Sun, leaf (green cells with chloroplasts), air, roots and stem, rest of the plant. Arrows: Sun to leaf; roots and stem to leaf; air to leaf; leaf to air; leaf to rest of the plant. Every arrow is labeled. Table (model data), carbon dioxide level in a sealed clear box holding a potted plant, in units: start, 400; after 6 hours in bright light, 300; after 6 more hours in the dark, 350.

9. 5.

   Milo reads two figures. Why did the carbon dioxide level fall during the 6 hours of light?

   • The roots pushed the carbon dioxide into the soil
   • The plant gave off carbon dioxide while making sugar
   • The plant took in carbon dioxide to make sugar
   • The light turned the carbon dioxide into energy
10. 6.

    Noah reads two figures. Why did the carbon dioxide level rise again during the 6 hours of dark?

    • Carbon dioxide leaked out of the potting soil
    • The plant turned stored light into carbon dioxide
    • The plant made even more sugar in the dark than it did in the light
    • No sugar was made, but the cells still released carbon dioxide
11. 7.

    Pia’s teacher coats the underside of some leaves with petroleum jelly. Use both figures to predict the result for those leaves.

    • Less sugar, because light cannot pass the jelly underneath
    • Less sugar, because carbon dioxide cannot enter the leaf
    • More sugar, because the oxygen cannot leave the leaf
    • No change, because the roots supply the carbon
12. 8.

    Ren grows a bean seedling in a dark box. It grows tall and pale for a week. How can it grow with no light?

    • Its roots take in sugar from the water
    • It uses food stored in the seed by the parent plant
    • It uses up the light it took in before it was planted
    • It makes sugar from the soil in the dark

13. Use this

    Drawing of a leaf with green patches and white patches, not to scale. Test result (read about; an adult did a starch test): starch, the stored form of sugar, found in the green parts, none in the white parts.

14. 9.

    Tala reads about a leaf with green and white patches kept in light. A starch test found stored sugar in the green parts but not the white parts. Why?

    • The white parts got less light than the green parts
    • The white parts lack the green chloroplasts that make sugar
    • The white parts take sugar from the soil instead
    • The white parts give off carbon dioxide instead of oxygen
15. 10.

    Bubbles in 10 minutes under the same lamp: tap water, 40; boiled and cooled water, 8. Zee reads that a water plant gave off fewer bubbles in water an adult had boiled and cooled first. Which explains it?

    • Boiling took the plant food out of the water
    • The cooled water blocked the lamp’s light
    • Boiling removed carbon dioxide, an input the plant needs
    • Boiling took out the oxygen that the plant needs to take in