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Interpret Data Relating to Osmosis

Worksheet Overview

QUESTION 1 of 10

Ever wondered why your urine is often darker and more concentrated in the summer? Probably not, it's not the nicest thing to be thinking about! But often it's because we tend to sweat more in summer months so we lose a lot more water. Our kidneys then will try and keep a hold of more water for many of our important processes resulting in more concentrated urine! This movement of water into and out of our cells is called osmosis.

  

                                                           Image of particles moving via osmosis

 

Osmosis is the diffusion of water molecules from a high concentration of water to a low concentration of water, across a partially permeable membrane.  A partially permeable membrane has holes or pores in it that allow water molecules through but are too small to allow larger molecules through. 

During osmosis, water molecules diffuse from pure water or dilute solution to more concentrated solutions.

Dilute solutions have a high concentration of water molecules so have a high water potential.

Concentrated solutions have a low concentration of water molecules so have a  low water potential.


 

Osmosis in organisms

Plant and animal cells are surrounded by a partially permeable plasma membrane. This allows water and other small molecules to diffuse across. Plant cells additionally have a strong cell wall surrounding the membrane which offers support and protection. Animal cells don't have a cell wall. This means they respond differently to plant cells in the gaining and losing of water.

 

                                                         Image of osmosis occurring in red blood cells

 

In dilute solutions, osmosis can cause animals cells, such as red blood cells, to swell up and sometimes even burst (beaker B in the image above). This is because water will move from a high water potential outside the cell to a low water potential inside the cell. In concentrated solutions (where there is less water present),  water loss causes the cells to shrink (beaker C). Animal cells need to maintain a balance, this means that the water concentration both inside and outside the cell are equal (beaker A).

 

                                                                    Image of plant cells in different concentrations of water

 

Plants require water in order to photosynthesise. The roots of a plant contain root hair cells which are specialised cells that increase the surface area of the cells for maximum absorption of water by osmosis. In pure water, plant cells will take in water via osmosis and become firm or turgid. In a concentrated solution (not much water present),  the cell loses water and starts to shrink and becomes flaccid.  

 

In humans, the concentration of water and salt in the blood is controlled by the kidneys. The kidneys ensure that our bodies have the right concentration of water and get rid of the excess water as urine.


 

Calculations Involving Osmosis


                                                                                 Image of weighing scales


Osmosis can be demonstrated using cubes of potatoes of roughly the same mass. Placing the cubes in different concentrations of sugar solutions, the cubes might gain or lose mass, or might even stay the same mass.

 

Scientists will be able to calculate the percentage change in mass to see how much mass was gained or lost  - converting to percentages often makes for an easier comparison. Percentage mass is calculated by using the following equation:

 

                                                                    ((Final mass – initial mass) ÷ initial mass x 100

 

For example, a potato cube has an initial mass of 1 g. After placing it in a sugar solution for 30 minutes, its mass was 1.1 g. Its percentage change in mass is 10%. 

((1.1 g - 1 g) ÷ 1 g x 100 = +10%

The plus sign shows there was an increase in mass. A minus sign shows a loss in mass.


 

The rate of water uptake can also be calculated. This gives an indication of how much water is absorbed in an hour. The rate of uptake is calculated using the following equation:

 

Change in mass (g) x (60 minutes ÷ duration of time in minutes)

 

Using the above example of the potato cube:


0.1 g x (60 mins ÷ 30 mins) = 0.2  g/hour


 

In the following activity, you will interpret data relating to osmosis. 

Image of particles moving via osmosis

 

Plant and animal cells use the process of osmosis to transport water into or out of their cells. Describe osmosis. 

 

 

 

Image of particles moving via osmosis

 

Cell membranes are partially permeable. What is a partially permeable membrane? 

A partially permeable membrane does not have holes in it

A partially permeable membrane has holes in it

It only allows waste products through

It allows water molecules through but the holes are too small to allow larger molecules through

Osmosis can be demonstrated using cubes of potatoes of roughly the same mass. Placing the cubes in different concentrations of sugar solutions, the cubes might gain or lose mass, or might even stay the same mass.

Lara did an experiment at school on the effect of sugar solutions on potato pieces.  The potato pieces were of equal size. She measured the mass of each potato cube and placed each one in a beaker containing different concentrations of sugar solution. After two hours, the mass of each potato cube was measured.

 

Beaker  1 2 3 4 5
Sugar concentration (M)  0.2 0.4 0.6 0.8 1
Initial mass (g) 2 2 2 2 2
Final mass (g) 2.20 2.15 1.96 1.80 1.73
% change in mass (a) 7.5 -2 -10 (b)

 

Calculate the percentage change in mass in beaker 1 (a) and beaker 5 (b)

a) 10%

b) -8%

a) -10%

b) -13.5%

Lara did an experiment at school on the effect of sugar solutions on potato pieces.  The potato pieces were of equal size. She measured the mass of each potato cube and placed each one in a beaker containing different concentrations of sugar solution. After two hours, the mass of each potato cube was measured.

 

Beaker  1 2 3 4 5
Sugar concentration (M)  0.2 0.4 0.6 0.8 1
Initial mass (g) 2 2 2 2 2
Final mass (g) 2.20 2.15 1.96 1.80 1.73
% change in mass +10 +7.5 -2 -10 -13.5

 

Explain why the mass of the potatoes decreased in beakers 3, 4 and 5. 

Water entered the potato for respiration

Water left the potato cells by osmosis

The concentration of water outside the cells was lower than inside the cells

The concentration of water outside the cells was lower than inside the cells

 

 

 Image of water molecules Image of water moleculesImage of water molecules

Cell A 

 < Permeable membrane

 Image of water moleculesImage of water molecules

Image of water molecules

Cell B

 

The diagram above shows two cells separated by a permeable membrane. Cell A and cell B have twelve molecules of water each. Which direction will the water move? 

From cell A to cell B

From cell B to cell A

No net movement

Lara did an experiment at school on the effect of sugar solutions on potato pieces.  The potato pieces were of equal size. She measured the mass of each potato cube and placed each one in a beaker containing different concentrations of sugar solution. After 50 minutes, the mass of each potato cube was measured.  

 

Beaker  1 2 3 4 5
Sugar concentration (M)  0.2 0.4 0.6 0.8 1
Initial mass (g) 2 2 2 2 2
Final mass (g) 2.20 2.15 1.96 1.80 1.73
% change in mass +10 +7.5 -2 -10 -13.5

 

Calculate the rate of uptake in an hour for beaker 2.

 

0.24

0.20

0.18

Image of osmosis occurring in red blood cells

 

The beakers above show red blood cells in different concentrations of sugar solutions.

Which beaker shows a solution with the highest water potential in comparison to the red blood cells? 

Image of osmosis occurring in red blood cells

 

The beakers above show red blood cells in different concentrations of sugar solutions.

 

One of the beakers shows red blood cells in an isotonic solution. Do you know which one it is?

 Match up the descriptions below to describe what is happening in each beaker.

Column A

Column B

A
More water is entering the red blood cells than le...
B
More water is leaving the red blood cells than ent...
C
Water is entering and leaving the red blood cells ...

Osmosis can be demonstrated using cubes of potatoes of roughly the same mass. Placing the cubes in different concentrations of sugar solutions, the cubes might gain or lose mass, or might even stay the same mass.

Lara did an experiment at school on the effect of sugar solutions on potato pieces.  The potato pieces were of equal size. She measured the mass of each potato cube and placed each one in a beaker containing different concentrations of sugar solution. After two hours, the mass of each potato cube was measured.

 

Beaker  1 2 3 4 5
Sugar concentration (M)  0.2 0.4 0.6 0.8 1
Initial mass (g) 2 2 2 2 2
Final mass (g) 2.20 2.15 1.96 1.80 1.73

 

Calculate the change in mass in beaker 2 and beaker 3.

Column A

Column B

A
More water is entering the red blood cells than le...
B
More water is leaving the red blood cells than ent...
C
Water is entering and leaving the red blood cells ...

Image of flaccid plant cell

The above image is of a plant cell. What is happening to the water in this cell? 

Column A

Column B

A
More water is entering the red blood cells than le...
B
More water is leaving the red blood cells than ent...
C
Water is entering and leaving the red blood cells ...
  • Question 1

Image of particles moving via osmosis

 

Plant and animal cells use the process of osmosis to transport water into or out of their cells. Describe osmosis. 

 

 

CORRECT ANSWER
EDDIE SAYS
Osmosis is really important for cells - they're able to get the water they need for different processes like photosynthesis. Like gases in diffusion, water molecules move from a less concentrated (more water) solution to a more concentrated (less water) solution.
  • Question 2

 

Image of particles moving via osmosis

 

Cell membranes are partially permeable. What is a partially permeable membrane? 

CORRECT ANSWER
A partially permeable membrane has holes in it
It allows water molecules through but the holes are too small to allow larger molecules through
EDDIE SAYS
A partially permeable membrane is selective and only allows water and small particles to pass through it.
  • Question 3

Osmosis can be demonstrated using cubes of potatoes of roughly the same mass. Placing the cubes in different concentrations of sugar solutions, the cubes might gain or lose mass, or might even stay the same mass.

Lara did an experiment at school on the effect of sugar solutions on potato pieces.  The potato pieces were of equal size. She measured the mass of each potato cube and placed each one in a beaker containing different concentrations of sugar solution. After two hours, the mass of each potato cube was measured.

 

Beaker  1 2 3 4 5
Sugar concentration (M)  0.2 0.4 0.6 0.8 1
Initial mass (g) 2 2 2 2 2
Final mass (g) 2.20 2.15 1.96 1.80 1.73
% change in mass (a) 7.5 -2 -10 (b)

 

Calculate the percentage change in mass in beaker 1 (a) and beaker 5 (b)

CORRECT ANSWER
a) 10%
b) -13.5%
EDDIE SAYS
To calculate the percentage change in mass: ((final mass – initial mass) ÷ initial mass x 100 beaker 1: 2.20 - 2 = 0.20 g 0.20 g ÷ 2 = 0.1 0.1 x 100 = 10% beaker 5: 1.73 - 2 = -0.27 g -0.27 g ÷ 2 = -0.135 -0.135 x 100 = -13.5%
  • Question 4

Lara did an experiment at school on the effect of sugar solutions on potato pieces.  The potato pieces were of equal size. She measured the mass of each potato cube and placed each one in a beaker containing different concentrations of sugar solution. After two hours, the mass of each potato cube was measured.

 

Beaker  1 2 3 4 5
Sugar concentration (M)  0.2 0.4 0.6 0.8 1
Initial mass (g) 2 2 2 2 2
Final mass (g) 2.20 2.15 1.96 1.80 1.73
% change in mass +10 +7.5 -2 -10 -13.5

 

Explain why the mass of the potatoes decreased in beakers 3, 4 and 5. 

CORRECT ANSWER
Water left the potato cells by osmosis
The concentration of water outside the cells was lower than inside the cells
EDDIE SAYS
Water moves from where it is more concentrated to where it is less concentrated. In beakers 3, 4 and 5, the concentration of sugar is high meaning the concentration of water will be high. The water will therefore move out of the potatoes resulting in a decrease in mass.
  • Question 5

 

 

 Image of water molecules Image of water moleculesImage of water molecules

Cell A 

 < Permeable membrane

 Image of water moleculesImage of water molecules

Image of water molecules

Cell B

 

The diagram above shows two cells separated by a permeable membrane. Cell A and cell B have twelve molecules of water each. Which direction will the water move? 

CORRECT ANSWER
No net movement
EDDIE SAYS
There are an equal number of water molecules in cell A and cell B, so water will continue to move at an equal rate between the cells.
  • Question 6

Lara did an experiment at school on the effect of sugar solutions on potato pieces.  The potato pieces were of equal size. She measured the mass of each potato cube and placed each one in a beaker containing different concentrations of sugar solution. After 50 minutes, the mass of each potato cube was measured.  

 

Beaker  1 2 3 4 5
Sugar concentration (M)  0.2 0.4 0.6 0.8 1
Initial mass (g) 2 2 2 2 2
Final mass (g) 2.20 2.15 1.96 1.80 1.73
% change in mass +10 +7.5 -2 -10 -13.5

 

Calculate the rate of uptake in an hour for beaker 2.

 

CORRECT ANSWER
0.18
EDDIE SAYS
To calculate the rate of uptake: change in mass x (60 minutes ÷ time measured in minutes) 0.15 x (60 ÷ 50) 0.15 x 1.2 = 0.18
  • Question 7

Image of osmosis occurring in red blood cells

 

The beakers above show red blood cells in different concentrations of sugar solutions.

Which beaker shows a solution with the highest water potential in comparison to the red blood cells? 

CORRECT ANSWER
B
EDDIE SAYS
Beaker B has red blood cells that are swollen. This means that the red blood cells must have a lower water potential in comparison to the solution they are in. Water moves into red blood cells from a high water potential to a lower water potential.
  • Question 8

Image of osmosis occurring in red blood cells

 

The beakers above show red blood cells in different concentrations of sugar solutions.

 

One of the beakers shows red blood cells in an isotonic solution. Do you know which one it is?

 Match up the descriptions below to describe what is happening in each beaker.

CORRECT ANSWER

Column A

Column B

A
Water is entering and leaving the...
B
More water is entering the red bl...
C
More water is leaving the red blo...
EDDIE SAYS
An isotonic solution is when the concentration of water is the same both inside and outside the cell. Water moves into and out of the cell at the same rate. This means that beaker A contains the isotonic solution.
  • Question 9

Osmosis can be demonstrated using cubes of potatoes of roughly the same mass. Placing the cubes in different concentrations of sugar solutions, the cubes might gain or lose mass, or might even stay the same mass.

Lara did an experiment at school on the effect of sugar solutions on potato pieces.  The potato pieces were of equal size. She measured the mass of each potato cube and placed each one in a beaker containing different concentrations of sugar solution. After two hours, the mass of each potato cube was measured.

 

Beaker  1 2 3 4 5
Sugar concentration (M)  0.2 0.4 0.6 0.8 1
Initial mass (g) 2 2 2 2 2
Final mass (g) 2.20 2.15 1.96 1.80 1.73

 

Calculate the change in mass in beaker 2 and beaker 3.

CORRECT ANSWER
EDDIE SAYS
To calculate the change in mass: (final mass – initial mass). For beaker 2: 2.15 - 2 = 0.15 g For beaker 3: 1.96 - 2 = -0.04 g
  • Question 10

Image of flaccid plant cell

The above image is of a plant cell. What is happening to the water in this cell? 

CORRECT ANSWER
EDDIE SAYS
A plant cell that has its cell membrane pulled away from the cell wall is showing a flaccid cell. All the water has left the cell by osmosis. It's a bit like using a straw to suck out all the juice from a carton - the carton loses its shape.
---- OR ----

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