Osmosis

A student investigated the effect of concentration of salt solution on the mass of potato cubes.

This is the method used.

1. Cut a piece of potato into four cubes.

2. Record the mass of each cube.

3. Put each cube into a different beaker.

4. Pour a different concentration of salt solution into each beaker.

5. After 1 hour, remove each cube.

6. Record the mass of each cube.

Suggest two improvements to the investigation.

The student improved the investigation.

Table 3 shows the results.

What was the concentration of the solution inside the potato cells?

Tick () one box.

Changes in mass of the potato cubes are due to water moving into and out of the cells.

What is the name of the process that allows water to move into and out of cells?

Tick () one box.

Figure 7 shows one of the potato cubes.

Calculate the surface area of the potato cube.

Give the unit.

The student then investigated the effect of surface area on the change in mass of a piece of potato.

Describe how the student could increase the surface area of the piece of potato shown in Figure 7.

Potatoes contain varying amounts of carbohydrates and proteins.

Starch and sugar are different types of carbohydrate.

Draw one line from each carbohydrate to the chemical used to test for the carbohydrate.

A potato was tested for protein, sugar and starch.

Table 4 shows the results.

Which substances were found in the potato?

Tick () one box.

A student investigated the effect of surface area on the mass of potato pieces placed in water.

This is the method used.

1. Cut 5 cylinders from one potato. Cut each cylinder to a length of 3 cm.

2. Cut 4 of the cylinders into different numbers of pieces.

3. Dry each piece of potato on a paper towel.

4. Record the mass of each group of potato pieces.

5. Put each group of potato pieces into different beakers containing distilled water as

shown in Figure 5.

6. After 30 minutes remove and dry each group of potato pieces.

7. Record the mass of each group of potato pieces.

8. Calculate the percentage increase in mass for each group of potato pieces.

Table 1 shows the results.

Why is it more valid to calculate the percentage increase in mass rather than using the increase in mass?

Describe the relationship between total surface area and percentage increase in mass.

Use Table 1.

Explain why the potato pieces increased in mass.

The student repeated the investigation.

The potato pieces were in the beakers of distilled water for 24 hours.

Explain what results would be expected after leaving the investigation set up for 24 hours.

The method used is repeated below.

1. Cut 5 cylinders from one potato. Cut each cylinder to a length of 3 cm.

2. Cut 4 of the cylinders into different numbers of pieces.

3. Dry each piece of potato on a paper towel.

4. Record the mass of each group of potato pieces.

5. Put each group of potato pieces into different beakers containing distilled water as

shown in Figure 5 on page 13.

6. After 30 minutes, remove and dry each group of potato pieces.

7. Record the mass of each group of potato pieces.

8. Calculate the percentage increase in mass for each group of potato pieces.

A different student wanted to investigate the effect of salt concentration on potato tissue.

Describe how the student could change the method to investigate the effect of salt concentration on potato tissue.

A student investigated the concentration of salt in solution Z.

The student used a method involving osmosis.

The student used tubing made of partially permeable membrane.

This is the method used.

1. Cut six pieces of tubing to the same length.

2. Tie one end of each piece of tubing.

3. Put the same volume of solution Z into each piece of tubing.

4. Tie the other end of each piece of tubing to form a sealed tube.

5. Record the mass of each tube.

6. Place each tube into a different concentration of salt solution.

7. After 2 hours, remove each tube from the salt solutions.

8. Record the mass of each tube.

Figure 8 shows one of the sealed tubes in a salt solution.

What was the independent variable for the investigation?

Tick (✓) one box.

The student dried the outside of each tube with a paper towel before recording the mass.

Why was it important to dry the tubes?

Table 3 shows the results.

Calculate value X in Table 3.

Give your answer to 1 decimal place.

Complete Figure 9.

You should:

• plot the percentage change in mass from Table 3 for salt concentrations of only 0.2 mol/dm³ to 1.0 mol/dm³

• draw a line of best fit.

One of the results has been plotted for you.

Determine the concentration of salt in solution Z.

Use Figure 9.

A student investigated the concentration of salt in solution Z.

The student used a method involving osmosis.

The student used tubing made of partially permeable membrane.

This is the method used.

1. Cut six pieces of tubing to the same length.

2. Tie one end of each piece of tubing.

3. Put the same volume of solution Z into each piece of tubing.

4. Tie the other end of each piece of tubing to form a sealed tube.

5. Record the mass of each tube.

6. Place each tube into a different concentration of salt solution.

7. After 2 hours, remove each tube from the salt solutions.

8. Record the mass of each tube.

Figure 1 shows one of the sealed tubes in a salt solution.

What was the independent variable for the investigation?

Tick (✓) one box.

The student dried the outside of each tube with a paper towel before recording the mass.

Why was it important to dry the tubes?

Table 1 shows the results.

Calculate value X in Table 1.

Give your answer to 1 decimal place.

Complete Figure 2.

You should:

• plot the percentage change in mass from Table 1 for salt concentrations of only 0.2 mol/dm³ to 1.0 mol/dm³

• draw a line of best fit.

One of the results has been plotted for you.

Figure 2

Determine the concentration of salt in solution Z.

Use Figure 2.

A student investigated the effect of different concentrations of sugar solution on pieces of potato. This is the method used.

1. Cut five pieces of potato.

2. Record the starting mass of each piece of potato.

3. Place each piece of potato in a different concentration of sugar solution.

4. After 24 hours remove the pieces of potato from the solutions.

5. Record the final mass of each piece of potato.

6. Calculate the change in mass for each piece of potato.

What is the independent variable? Tick (✓) one box.

Table 3 shows the results.

Explain why the potato in 0.0 mol/dm³ sugar solution increased in mass.

Complete Figure 5. Some of the results have been plotted for you. You should:

• plot the data from Table 3

• draw a line of best fit through all the points.

The mass of a piece of potato does not change when: concentration of solution inside cells = concentration of solution outside cells

Determine the concentration of sugar solution inside the potato cells. Use Figure 5.

Table 3 is repeated below.

Calculate the percentage change in mass for the potato in 0.2 mol/dm³ sugar solution. Use Table 3. Use the equation:

Give your answer to 3 significant figures.

A student investigated the effect of different concentrations of sugar solution on pieces of potato. This is the method used.

1. Cut five pieces of potato.

2. Record the starting mass of each piece of potato.

3. Place each piece of potato in a different concentration of sugar solution.

4. After 24 hours remove the pieces of potato from the solutions.

5. Record the final mass of each piece of potato.

6. Calculate the change in mass for each piece of potato.

What is the independent variable? Tick (✓) one box.

Table 1 shows the results.

Explain why the potato in 0.0 mol/dm³ sugar solution increased in mass.

Complete Figure 1. Some of the results have been plotted for you. You should:

• plot the data from Table 1

• draw a line of best fit through all the points.

The mass of a piece of potato does not change when: concentration of solution inside cells = concentration of solution outside cells

Determine the concentration of sugar solution inside the potato cells. Use Figure 1.

Table 1 is repeated below.

Calculate the percentage change in mass for the potato in 0.2 mol/dm³ sugar solution. Use Table 1. Use the equation:

Give your answer to 3 significant figures.

A student investigated the effect of different concentrations of sugar solution on pieces of potato.

This is the method used.

1. Cut three pieces of potato to the same length.

2. Dry each piece on a paper towel.

3. Weigh each piece.

4. Place each piece in a different concentration of sugar solution.

5. Leave all three pieces for 2 hours.

6. Remove the three pieces of potato from the solutions.

7. Dry each piece on a paper towel.

8. Measure the length and mass of each piece of potato.

Figure 6 shows how the investigation was set up.

Why did the student dry each piece of potato before weighing it?

What two changes would you expect in the potato in tube A after 2 hours?

Tick two boxes.

Complete the sentences.

than the solution inside the potato cells.

The potato in tube B did not change.

Give one conclusion that can be made from this observation.

Figure 7 shows the root of a germinating seed.

Describe two ways the root is adapted to absorb water efficiently.

A student investigated the effect of different concentrations of sugar solution on pieces of carrot. This is the method used.

1. Weigh five pieces of carrot.

2. Place each piece into a different tube.

3. Into each tube add 20 cm³ of water or one of the sugar solutions as shown in

Figure 6

4. Leave the apparatus for 2 hours.

5. Remove the carrot and dry each piece on paper towel.

6. Reweigh each piece.

7. Calculate the percentage (%) change in mass of each piece.

Figure 6 shows how the investigation was set up.

Table 2 shows the results.

Suggest why the student calculated the percentage (%) change in mass of each piece of carrot.

Complete Figure 7 using the results in Table 2

• Choose a suitable scale and label for the y-axis.

• Plot the results.

• Draw a line of best fit.

Estimate the concentration of sugar solution inside the carrot cells. Use your completed graph on Figure 7

Explain why the mass of the carrot in the 0.6 mol/dm³ sugar solution changed.

The student repeated the investigation using boiled pieces of carrot. The pieces of carrot did not change in mass. Suggest why.