MYTUTOR SUBJECT ANSWERS

360 views

What is diffusion?

For the exams, the definition you will need to know is that "diffusion is the net movement of a substance from an area of high concentration to an area of low concentration, down a diffusion gradient".

But what does this actually mean?

Imagine a box filled with many butterflies, separated by a wall in the middle. The ones on the left are red, and the ones on the right are blue. The butterflies are flying around at random on their respecive sides. At this point, the concentration of red butterflies on the left is high, and on the right is low. The concentration of blue butterflies on the right is high, and on the left is low.

The wall is removed. The red butterflies are free to fly to the right hand side, which they will, to avoid being bunched up together. In other words, they move from an area of high concentration of red butterflies to an area of low concentration of red butterflies. The same goes for the blue butterflies on the right - they will move onto the left hand side when the wall is removed.

It is important to note that the butterflies do not "decide" to move away from the others of their colour. They simply move at random into all the space available, which naturally means they will spread out into the new space made by removing the wall. Some may go back to their original side, then maybe cross back over again, it doesn't matter. Until there are equal numbers of blue and red butterflies on each side, each colour will show a net movement from high to low concentration (in other words, more butterflies are moving from high to low than move from low to high concentration). This is called moving down a diffusion gradient, in the same way that moving from high land to low land would be moving down the gradient of a hill.

The same happens with particles. Because they move at random, they will spread out from an area where there is lots of them, to an area where there are not as many. Think of ribena - if you have a glass of water and add ribena, you can see the two different colours separately. But if you come back in a few hours, the ribena will have completely mixed with the water so it all looks the same colour. This is diffusion, as the two different types of particles have spread out into each other (from a high concentration to a low concentration) until their concentrations are equal. 

Emily R. GCSE Biology tutor, GCSE Chemistry tutor, GCSE Physics tutor...

1 year ago

Answered by Emily, a GCSE Biology tutor with MyTutor

Still stuck? Get one-to-one help from a personally interviewed subject specialist

187 SUBJECT SPECIALISTS

£20 /hr

Oliver W.

Degree: Natural Sciences (Bachelors) - Cambridge University

Subjects offered: Biology, Maths+ 4 more

Biology
Maths
Extended Project Qualification
Economics
Chemistry
-Personal Statements-

“I am third year student at the University of Cambridge studying Natural Sciences. I specialise in Neurobiology. However, I have a lot of experience in othersciences and maths, at GCSE and IB level. I studied for 5 years at Sevenoaks Sc...”

£18 /hr

Oliver H.

Degree: Medicine (Bachelors) - Bristol University

Subjects offered: Biology, Science+ 5 more

Biology
Science
Maths
English
Chemistry
-Personal Statements-
-Medical School Preparation-

“About me & what you can expect I am a medical student at Bristol University with a passion for Biology, Chemistry and English. I have had lots of experience teaching, having tutored biology and chemistry extensively and spent my summe...”

£18 /hr

Firat G.

Degree: Biochemistry (Bachelors) - Bristol University

Subjects offered: Biology, Economics+ 1 more

Biology
Economics
Chemistry

“Currently, I am studying Medicinal Biochemistry at the University of Bristol. I tutor numerous students at both GCSE and A level and thoroughly enjoy being able to help individuals improve their confidence and understanding of Biology ...”

About the author

Emily R.

Currently unavailable: for new students

Degree: A100 Medicine (Bachelors) - Newcastle University

Subjects offered: Biology, Physics+ 3 more

Biology
Physics
Chemistry
-Personal Statements-
-Medical School Preparation-

“About me My name is Emily, I live in Cumbria, and I’m a second year medical student at Newcastle University.  I gained three A*s in science subjects at A-level, however my passion for science is not represented in my grades but i...”

MyTutor guarantee

You may also like...

Other GCSE Biology questions

Where is water absorbed in the digestive system? - Duodenum, Ileum or colon?

What is mitosis?

What is active transport?

How do we regulate body temperature?

View GCSE Biology tutors

Cookies:

We use cookies to improve our service. By continuing to use this website, we'll assume that you're OK with this. Dismiss

mtw:mercury1:status:ok