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

Grade 7 Science Worksheet - Challenge Me

Circle the best answer.

1. 1.

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

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

   Bo’s friend says plants take in oxygen and give out carbon dioxide when they make sugar. Which response is best?

   • Disagree: plants trade no gases with the air
   • Agree: plants trade gases the very same way people do when breathing
   • Disagree: making sugar takes in carbon dioxide and gives off oxygen
   • Agree: that is why plants need fresh air

3. Read this first

   Investigation card

   Plant 1 sat in a sunny window and was watered every day. Plant 2 sat in a dark closet and was watered once a week. After two weeks Plant 1 was taller.

4. 3.

   Kira tested whether light helps a plant grow. What is the flaw in this test?

   • Two things changed, light and water, so the cause is unclear
   • Plant height is not a thing a class can measure
   • Both plants should have been kept in the dark the whole time
   • There is no flaw, because light caused the growth

5. 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.

6. 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
   • The lamp plant took in oxygen from the jar
   • Light turned into the gas in the bubbles
   • Light is needed for the plant to give off oxygen

7. 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.

8. 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 took in carbon dioxide to make sugar
   • The plant gave off carbon dioxide while making sugar
   • The light turned the carbon dioxide into energy
9. 6.

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

   • The plant made even more sugar in the dark than it did in the light
   • The plant turned stored light into carbon dioxide
   • No sugar was made, but the cells still released carbon dioxide
   • Carbon dioxide leaked out of the potting soil
10. 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 carbon dioxide cannot enter the leaf
    • No change, because the roots supply the carbon
    • Less sugar, because light cannot pass the jelly underneath
    • More sugar, because the oxygen cannot leave the leaf
11. 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 makes sugar from the soil in the dark
    • It uses up the light it took in before it was planted

12. 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.

13. 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
14. 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?

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