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Define Diffusion

In this worksheet, students will define diffusion.

Worksheet Overview

QUESTION 1 of 10

Image of a pair of socks

 

 

Why can you smell someone's stinky PE socks from all the way across the classroom? Yuck! Normally it's because sweat and other molecules are moving away from the socks and spread out in the air. This is called diffusion

Diffusion is the spreading out of the particles of any substance in solution, or particles of a gas, resulting in movement from an area of higher concentration (where there are more particles in a certain solution or area) to an area of lower concentration (where there are fewer particles).  


Image of particles diffusing

 

Living organisms need different substances to survive and function. These substances need to be transported into and out of their cells through diffusion (as well as osmosis and active transport-you will learn more about these later!). During diffusion, molecules move from an area of high concentration to an area of low concentration. They are said to move down a concentration gradient. Particles diffuse until they are evenly spaced apart. Diffusion is a passive process which means that no energy is needed and it happens naturally. 

 

Image of gas exchange in alveolus

 

Diffusion in organisms

 

In multicellular organisms, surfaces and organ systems are specialised for exchanging materials. This is to allow sufficient molecules to be transported into and out of cells for the organism’s needs. Diffusion is the main way substances move over short distances in organisms.

 

Diffusion happens in the lungs where breathing involves exchanging gases in the lungs. When you breathe in, oxygen in the inhaled air diffuses through the tiny air sacs (alveoli) in your lungs into your bloodstream. The oxygen is transported around your body. Carbon dioxide is the waste gas produced by respiration. Carbon dioxide diffuses from cells into the bloodstream and is exhaled by the lungs

 

Image of villi in intestine

 

Another example of diffusion is in the small intestine. Digested food is broken down into small molecules such as glucose and amino acids. These important molecules need to be transported around the body via the blood. The small intestine is lined with many finger-like projections called villi. The molecules diffuse through the villi of the small intestine into the blood to be transported around the body.

 

Image of plant photosynthesising 

 

Diffusion also occurs in plants. The structure of the leaf is adapted for gas exchange. There are tiny pores called stomata, in the surface of the leaf. It is through here plants take in carbon dioxide for photosynthesis and produce oxygen. These enter and leave the plant through the process of diffusion.

 

Factors affecting diffusion

Different factors can affect diffusion and how quickly it happens. Some of these factors are:

- the difference in concentrations (concentration gradient) - having a large difference in concentrations means that diffusion can occur at a quicker rate as particles will naturally move from a high to low concentration. 
- the temperature - the higher the temperature the more energy the particles will have to move and spread out.
- the surface area of the membrane - the larger the surface area, the faster the rate of diffusion. This is because more particles can pass through the membrane as there is more area, like in the alveoli in the lungs.

 

In the following activity, you will define and describe diffusion.

Image of noseImage of a pair of socks

 

Stuart can smell someone's smelly socks in class. How can he smell socks from a distance?

Stuart has a really good sense of smell

The socks are REALLY smelly

The sweat particles diffuse into the air from the socks and spread out

Image of noseImage of a pair of socks

 

Stuart can smell someone's smelly socks in class. Where is the smell strongest

The smell is strongest at the sock

The smell is strongest away from the sock

The smell is strongest everywhere

Describe the process of diffusion by filling in the blanks below.

 

Image of particles diffusing

The smell is strongest at the sock

The smell is strongest away from the sock

The smell is strongest everywhere

Image of plant photosynthesisingImage of gas exchange in alveoli

 

Diffusion allows many important processes to occur in different organisms.

Oxygen entering the blood from the lungs

Carbon dioxide entering the lungs from the blood

Carbon dioxide entering the leaf of a plant for photosynthesis

Water entering the lungs

Why is diffusion important?

Oxygen entering the blood from the lungs

Carbon dioxide entering the lungs from the blood

Carbon dioxide entering the leaf of a plant for photosynthesis

Water entering the lungs

Diffusion is a process that doesn't need energy. What is another name for not needing energy?

 O O O O O

Cell A 

 O O O O O O O O O O O

Cell B

 

 

The diagram above shows two cells. Cell A has five particles and Cell B has eleven particles. Which direction will the particles diffuse?

From Cell A to Cell B

From Cell B to Cell A

No movement

The rate of diffusion is affected by different factors. Match up the sentences describing how these factors affect the rate of diffusion.

Column A

Column B

The greater the difference in concentration...
...the more space for particles to move through, r...
The greater the temperature...
...the greater the movement of particles, resultin...
The greater the surface area...
...the faster the rate of diffusion because more p...

What is the name of the structure of the plant where gas exchange happens?

Certain gases diffuse into and out of plants. What are these gases needed for?

For absorbing water

For photosynthesis

For metabolism

image of a plant

 

Which gases diffuse into and out of the plant due to photosynthesis?

Hydrogen

Carbon dioxide

Nitrogen

Oxygen

  • Question 1

Image of noseImage of a pair of socks

 

Stuart can smell someone's smelly socks in class. How can he smell socks from a distance?

CORRECT ANSWER
The sweat particles diffuse into the air from the socks and spread out
EDDIE SAYS
The socks can be smelt because sweat and other molecules are moving away from it and spreading out in the air. This is called diffusion.
  • Question 2

Image of noseImage of a pair of socks

 

Stuart can smell someone's smelly socks in class. Where is the smell strongest

CORRECT ANSWER
The smell is strongest at the sock
EDDIE SAYS
The socks can be smelt because the sweat molecules are moving away from the socks and spreading out in the air. The smell becomes weaker further away from the sock. Maybe Stuart needs to sit further away from the person with smelly socks on!
  • Question 3

Describe the process of diffusion by filling in the blanks below.

 

Image of particles diffusing

CORRECT ANSWER
EDDIE SAYS
In diffusion particles will move from more concentrated areas to low concentrated areas down a concentration gradient. This is a pretty standard answer when describing diffusion so it's worth remembering for your exams.
  • Question 4

Image of plant photosynthesisingImage of gas exchange in alveoli

 

Diffusion allows many important processes to occur in different organisms.

CORRECT ANSWER
Oxygen entering the blood from the lungs
Carbon dioxide entering the lungs from the blood
Carbon dioxide entering the leaf of a plant for photosynthesis
EDDIE SAYS
Diffusion allows gas exchange to occur in the lungs of humans-there is a higher concentration of oxygen in the lungs compared to the blood, so oxygen moves into the blood. Carbon dioxide does the opposite and moves from the blood to the lungs to be exhaled. Carbon dioxide, oxygen and water vapour also diffuse into and out of the leaves of a plant.
  • Question 5

Why is diffusion important?

CORRECT ANSWER
EDDIE SAYS
Diffusion is really important for cells to get the things they need for different processes like respiration or photosynthesis. At the same time, diffusion allows cells to get rid of waste products too.
  • Question 6

Diffusion is a process that doesn't need energy. What is another name for not needing energy?

CORRECT ANSWER
passive
EDDIE SAYS
Particles move from a high concentration to a low concentration-this process doesn't need energy. You can imagine it as a ball rolling down a hill compared to trying to roll a ball uphill. Rolling downhill won't require your energy whereas trying to roll a ball uphill would!
  • Question 7

 O O O O O

Cell A 

 O O O O O O O O O O O

Cell B

 

 

The diagram above shows two cells. Cell A has five particles and Cell B has eleven particles. Which direction will the particles diffuse?

CORRECT ANSWER
From Cell B to Cell A
EDDIE SAYS
Particles will move from a higher concentration to a lower concentration. Cell B has more particles than Cell A so particles will move out of Cell B and into Cell A until there are equal numbers of particles in each cell.
  • Question 8

The rate of diffusion is affected by different factors. Match up the sentences describing how these factors affect the rate of diffusion.

CORRECT ANSWER

Column A

Column B

The greater the difference in con...
...the faster the rate of diffusi...
The greater the temperature...
...the greater the movement of pa...
The greater the surface area...
...the more space for particles t...
EDDIE SAYS
Take the time to remember these key factors as you are often asked about them in exams. Maybe you can try this question a few times to consolidate your knowledge.
  • Question 9

What is the name of the structure of the plant where gas exchange happens?

CORRECT ANSWER
Stomata
Stoma
EDDIE SAYS
The stomata are really important, they are the pores where carbon dioxide enters for photosynthesis and oxygen leaves.
  • Question 10

Certain gases diffuse into and out of plants. What are these gases needed for?

CORRECT ANSWER
For photosynthesis
EDDIE SAYS
Carbon dioxide and oxygen are needed for photosynthesis to occur. Without these gases, plants won't be able to respire and grow.
  • Question 11

image of a plant

 

Which gases diffuse into and out of the plant due to photosynthesis?

CORRECT ANSWER
Carbon dioxide
Oxygen
EDDIE SAYS
Carbon dioxide is an important gas needed for photosynthesis. Oxygen is released into the atmosphere as a product of photosynthesis. Both gases diffuse in and out of the plant.
---- OR ----

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