Diffusion Flashcards
What is Diffusion?
Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration.
Net Movement - The movement of all of the particles considered together as a group.
Diffusion can happen in what 2 states of matter?
Gases and Liquids
Diffusion can also take place through some materials - Cell Membranes.
If only some molecules can diffuse through the cell membrane, what would be the term for this?
Partially Permeable
Meaning only some molecules can diffuse through.
Only smaller molecules like water, glucose and amino acids are able to diffuse through. Whereas larger molecules cannot fit through the membrane because they are too big, such as things like proteins and starch.
Diffusion does not require any energy from the cell. What is the term for this?
Diffusion is a passive process.
What are the 3 factors that affect the rate of diffusion?
- Concentration Gradient
This is just the difference in concentration between 2 places. The larger the concentration gradient between 2 places, the higher the rate of diffusion.
- Temperature
Higher temperatures give the particles more energy, meaning all the particles will move around faster, and so overall they will diffuse more quickly. A higher temperature means a higher rate of diffusion.
- Surface Area
The larger the surface area, the higher the rate of diffusion. This is because if something has a larger surface area, more particles can fit around its surface, so more particles can be diffusing in and out at once.
How do you investigate diffusion in a non-living system?
Phenolphthalein is a pH indicator - it’s pink in alkaline solutions and colourless in acidic solutions. You can use it to investigate diffusion in agar jelly:
- First, make up some agar jelly with phenolphthalein and dilute sodium hydroxide. This will make the jelly a shade of pink.
- Put some dilute hydrochloric acid in a beaker.
- Cut out a few cubes from the jelly and put them in the beaker of acid.
- If you leave the cubes for a while, they’ll eventually turn colourless as the acid diffuses into the agar jelly and neutralises the sodium hydroxide.
You can investigate the rate of diffusion by using different sized cubes of agar jelly and timing how long it takes for each cube to go colourless. The cube with the largest surface area to volume ratio will lose its colour quickest.
