Diffusion and osmosis

Grade 9 Science Worksheet

Circle the best answer.

1. 1.

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

   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 the cell spends energy to move carbon dioxide out
   • Both gases move in, because the outside holds more molecules in total
   • Oxygen moves in and carbon dioxide out, each down its own gradient
   • Oxygen moves out and carbon dioxide moves in, because gases swap places
3. 3.

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

4. Read this first

   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.

5. 4.

   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.

   • 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
   • Under 40 seconds, since heavier molecules diffuse faster
6. 5.

   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?

   • Osmosis: chloride ions crossing toward the side with more water
   • Facilitated diffusion: through a protein, using energy from the cell
   • Facilitated diffusion: passive, through a protein, down the gradient
   • Simple diffusion: passing between the tails, down the concentration gradient
7. 6.

   Noah sorts four transport events shown on a membrane drawing. Which event is simple diffusion?

   • Carbon dioxide slips between the tails, powered by cell energy
   • Chloride ions pass through channel L, down their gradient
   • Oxygen slips between the tails, down its gradient, with no protein
   • Glucose binds carrier M, which spends cell energy to change shape
8. 7.

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

9. 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.

10. 8.

    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 left arm, because water moves toward the side with less sugar
    • The right arm, because water moves toward the side with more sugar
    • The right arm, because the sugar dots cross to the right
    • Neither arm, because water stops moving when the arms start level
11. 9.

    Solute dots cannot cross either membrane. Each side is the same size. Tala reads two lab chambers, each split by a membrane that passes water but not solute. In which chamber does water move on net, and which way?

    • Chamber 1, from side B to side A, where solute is lower
    • Chamber 2, from side A to side B, because its sides are equal
    • Chamber 1, from side A to side B, where solute is higher
    • Both chambers, from side A to side B, since water moves in one direction
12. 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 2, because its arms differ more in sugar, so water moves faster
    • Tube 2, because the membrane spends more energy on a bigger difference
    • Tube 1, because its arms are closer to equal, so water moves faster
    • The tubes match, because water moves toward the right arm in both