Diffusion and osmosis

Grade 9 Science Worksheet

Circle the best answer.

1. Read this first

   Use this

   Lab card (model data). Coloring particles in two chambers joined by a membrane they can cross. Table with 3 rows. Columns: Time (minutes) | Left chamber | Right chamber. Rows: 0 | 24 | 0; 5 | 16 | 8; 10 | 13 | 11. A teacher ran the test; read about only.

2. 1.

   Ari's class reads counts of food-coloring particles in two chambers joined by a membrane they can cross. What will the counts be after a long time?

   • About 12 in each chamber, with particles no longer crossing
   • About 24 in the right chamber, because particles end up on the far side
   • About 12 in each chamber, though no particle crosses back to the left
   • About 12 in each chamber, with particles still crossing both ways
3. 2.

   Lab membrane drawing (model, not to scale). Dots of one substance can cross the membrane. Bo watches a model: side 1 holds 18 dots and side 2 holds 6. A teacher adds 12 dots to side 2. What happens next?

   • The dots keep moving from side 1 to side 2 until side 2 holds more
   • The dots stop moving, since the two sides are equal
   • The dots move from side 2 to side 1, because side 2 was added last
   • There is no net movement, though the dots keep moving both ways
4. 3.

   No proteins are drawn. Esme reads a drawing with two gases near a cell membrane. Each gas crosses the bilayer alone. Which statement predicts the net movement?

   • Oxygen moves in and carbon dioxide out, each down its own gradient
   • Both gases move in, because the outside holds more molecules in total
   • Oxygen moves in, and the cell spends energy to move carbon dioxide out
   • Oxygen moves out and carbon dioxide moves in, because gases swap places

5. Use this

   Lab card (model data). Time for food coloring to spread to the far side of a cup. Table with 2 rows. Columns: Water | Time to spread (seconds). Rows: warm water | 30; cold water | 90. The cups were the same size and held the same amount of water. A teacher ran the test; read about only.

6. 4.

   Jun's class drops food coloring into two cups of water and times how long the color takes to reach the far side. What does the card show?

   • Warmer water speeds diffusion, because particles have more thermal energy
   • The cups match, because diffusion is passive and needs no energy
   • Warmer water slows diffusion, because particles crowd together
   • Cold water spreads color faster, because dense water pushes particles along
7. 5.

   Kira compares two cells where oxygen crosses the bilayer alone. Which cell has the faster net diffusion, and why?

   • Cell 1, because the cell spends more energy when the gradient is steep
   • Cell 1, because a larger difference in concentration speeds diffusion
   • The rates match, because both cells have more oxygen outside
   • Cell 2, because molecules move faster when the sides are closer to equal

8. Use this

   Lab card (model data). Time for each substance to spread across a tank. Table with 2 rows. Columns: Substance | Molecule mass | Time to spread (seconds). Rows: L | lighter | 40; H | heavier | 100. Both tanks held the same warm water and the same starting gradient. A teacher ran the test; read about only.

9. 6.

   Luz's class reads a card with two substances in the same warm tank. A third substance, M, has molecules heavier than L's but lighter than H's. Predict M's time.

   • Under 40 seconds, since heavier molecules diffuse faster
   • Between 40 and 100 seconds, since heavier molecules diffuse more slowly
   • Exactly 140 seconds, since the two times add together
   • Exactly 40 seconds, since the same gradient gives the same time
10. 7.

    model, not to scale. Chloride ions cross a cell membrane through channel protein H, from 14 molecules outside to 5 inside. Milo classifies the transport. Which label fits?

    • Facilitated diffusion: passive, through a protein, down the gradient
    • Facilitated diffusion: through a protein, using energy from the cell
    • Osmosis: chloride ions crossing toward the side with more water
    • Simple diffusion: passing between the tails, down the concentration gradient
11. 8.

    Lab membrane drawing (model, not to scale). Pia reads a drawing of aquaporin channels in a lab membrane. Water crosses, but solute cannot. Which label fits the water movement?

    • Osmosis: passive movement of water toward the side with less solute
    • Osmosis: passive water movement toward the side with more solute
    • Facilitated diffusion: the cell spends energy to open the aquaporin
    • Osmosis: movement of water that the cell powers with its energy

12. Use this

    Lab drawing (model, not to scale). A U-tube with a selectively permeable membrane across the bottom. Water crosses it; sugar dots cannot. The left arm holds 2 sugar dots and the right arm holds 7 sugar dots. Both arms hold the same volume of fluid at the start.

13. 9.

    Ren's class reads about a U-tube with a membrane at the bottom that passes water but not sugar. The arms start at the same level. Which arm's level rises?

    • The right arm, because the sugar dots cross to the right
    • Neither arm, because water stops moving when the arms start level
    • The left arm, because water moves toward the side with less sugar
    • The right arm, because water moves toward the side with more sugar
14. 10.

    Zee compares two U-tubes with a membrane that passes water but not sugar. Which tube shows the faster net movement of water, and why?

    • Tube 1, because its arms are closer to equal, so water moves faster
    • Tube 2, because the membrane spends more energy on a bigger difference
    • Tube 2, because its arms differ more in sugar, so water moves faster
    • The tubes match, because water moves toward the right arm in both