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Define 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! 

Often, it's because we tend to sweat more in the summer months, so we lose a lot more water. Our kidneys then try to keep a hold of more water for many of our important processes, resulting in more concentrated urine!

 

Image of particles moving via osmosis

 Osmosis is the diffusion of water molecules from a low concentration solution to high concentration solution, 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. 

Concentrated solutions have a low concentration of water molecules

 

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 to the gain and loss 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 concentration outside the cell to a lower concentration inside the cell.  In concentrated solutions, water loss causes the cells to shrink (Beaker C in the image above). Animal cells need to maintain a balance. This means that the water concentration both inside and outside the cell are equal.

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, where there is 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 are controlled by the kidneys. The kidneys ensure we have the right concentration of water and getting rid of the excess water as urine.

 

In the following activity, you will define and describe 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. Fill in the blanks below to answer this question.

 

Image of particles moving via osmosis

Cell membranes are partially permeable. What is a partially permeable membrane? Choose two answers from below.

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 is too small to allow larger molecules through

image of orange juice

Lisa is drinking orange squash. She finds it too sweet, so adds more water to her glass of squash. What has she done to her orange squash?

 

Type your answer below. 

Image of red blood cells in water

What happens to red blood cells when they are placed in pure water? Select one answer below.

 

 

They lose water and shrink

They gain water and swell

They stay the same

Image of plant and roots

Water is absorbed by root hair cells in plants. The water will move from a high concentration to a low concentration.

 

Why do plants need water? Select one answer below.

 

For absorbing water

For photosynthesis

For metabolism

What is the name of the structure of the plant where water is absorbed by osmosis? Type one answer below.

Image of plant cells in different concentrations of water

Plants take in water through their root hair cells. If too much water is taken into the cells, the cells swell up. If there is too little water, what may happen?

 

Select two answers below.

The cell gains water

The cell loses water

The cell becomes flaccid

The cell stays the same

 Image of water molecules 

Cell A 

 < Permeable membrane

 Image of water moleculesImage of water molecules

Cell B

 

The diagram above shows two cells separated by a permeable membrane. Cell A has four molecules of water and Cell B has eight molecules of water.

 

Which direction will the water move? Select one answer below.

From Cell A to Cell B

From Cell B to Cell A

No movement

What do the following terms mean? Match up the key terms to the definitions.

Column A

Column B

Turgid
The cell shrinks as water is moving out of the cel...
Flaccid
Allows certain substances to pass through and not ...
Partially permeable
The cell swells as more water is moving into the c...

Image of chips

Sally was preparing potatoes to make some chips. She wanted to wash her raw potato chips so placed them in a bowl of pure water.

 

What is likely to happen to the mass of the potato chips? Select one answer below.

The mass stays the same

The mass increases

The mass decreases

  • 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. Fill in the blanks below to answer this question.

 

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 which 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? Choose two answers from below.

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

image of orange juice

Lisa is drinking orange squash. She finds it too sweet, so adds more water to her glass of squash. What has she done to her orange squash?

 

Type your answer below. 

CORRECT ANSWER
Diluted it
Dilute
EDDIE SAYS
Adding water to orange squash means you are diluting your drink. This means that the orange squash has more water to mix with, making it taste less sweet.
  • Question 4

Image of red blood cells in water

What happens to red blood cells when they are placed in pure water? Select one answer below.

 

 

CORRECT ANSWER
They gain water and swell
EDDIE SAYS
How did you do? Water will move into the red blood cells, making them swell up. If too much water enters, the cell can burst!
  • Question 5

Image of plant and roots

Water is absorbed by root hair cells in plants. The water will move from a high concentration to a low concentration.

 

Why do plants need water? Select one answer below.

 

CORRECT ANSWER
For photosynthesis
EDDIE SAYS
Water, as well as carbon dioxide and oxygen, are needed for photosynthesis to occur. Without these, plants won't be able to respire and grow.
  • Question 6

What is the name of the structure of the plant where water is absorbed by osmosis? Type one answer below.

CORRECT ANSWER
roots
root hair cell
EDDIE SAYS
The roots and root hair cells are really important, they are the structure where water enters for photosynthesis. Water passes into the root hair cells via osmosis.
  • Question 7

Image of plant cells in different concentrations of water

Plants take in water through their root hair cells. If too much water is taken into the cells, the cells swell up. If there is too little water, what may happen?

 

Select two answers below.

CORRECT ANSWER
The cell loses water
The cell becomes flaccid
EDDIE SAYS
Water moves from a higher concentration to a lower concentration. If the plant's surroundings are dry, then water leaves the plant cells, making cells flaccid. A bit like if you forget to water your plants they start to wilt!
  • Question 8

 Image of water molecules 

Cell A 

 < Permeable membrane

 Image of water moleculesImage of water molecules

Cell B

 

The diagram above shows two cells separated by a permeable membrane. Cell A has four molecules of water and Cell B has eight molecules of water.

 

Which direction will the water move? Select one answer below.

CORRECT ANSWER
From Cell B to Cell A
EDDIE SAYS
Is this getting easier? Water will move from a higher concentration to a lower concentration. There are more water molecules in Cell B than in Cell A, so water will move from Cell B through the partially permeable membrane and into Cell A until there are equal numbers of molecules in each cell.
  • Question 9

What do the following terms mean? Match up the key terms to the definitions.

CORRECT ANSWER

Column A

Column B

Turgid
The cell swells as more water is ...
Flaccid
The cell shrinks as water is movi...
Partially permeable
Allows certain substances to pass...
EDDIE SAYS
Take the time to remember these key terms, as you are often asked about them in exams. Maybe you can try this question a few times to consolidate your knowledge? Well done, that's another activity completed!
  • Question 10

Image of chips

Sally was preparing potatoes to make some chips. She wanted to wash her raw potato chips so placed them in a bowl of pure water.

 

What is likely to happen to the mass of the potato chips? Select one answer below.

CORRECT ANSWER
The mass increases
EDDIE SAYS
The water is pure, so the cells of the potato will have less water than its surroundings. Water will move into the potato chips, increasing their mass.
---- OR ----

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