A particle model of diffusion in liquids
Imagine the diffusion gradient from left to right for the green
particles added to the blue particles on the left. So, for the green
particles, net migration is from left to right (from a higher to a
lower concentration) and will continue, in
a sealed container, until all the particles are evenly distributed
(as pictured), then there is no net migration or change in
concentration throughout the mixture.
Diffusion is slower in liquids because there is less space between
the particles for other particles to move into and random collisions
will occur more frequently slowing down the particle spreading
effect down a diffusion gradient.
(7) Diffusion in a gel
This biology experiment
demonstrates slow diffusion in liquids, but note, although even
slower, the permeability of the gel towards molecules (water or
ions) is always present.
The gel cubes contain an alkali (dilute sodium
hydroxide) and phenolphthalein indicator that turns pink.
The gel cubes are placed in dilute hydrochloric
acid, which slowly diffuses into the gel cubes, neutralises the alkali and turns
the indicator colourless/
importance of diffusion and gas exchange in living organisms
For plant gas exchanges and photosynthesis
What is the
chemical process of photosynthesis?
Plant structure and photosynthesis - leaf adaptations
organ gas/nutrient exchanges see
Gas exchange in
the human lungs by diffusion, comments on breathing, COPD and ventilators
Gas exchange and the structure of fish gills
The function of villi in the exchange
surface of the small
structure adaptations in other animals
More on transport systems in plants and
A particle model and factors
affecting the rate of diffusion and Fick's Law of diffusion
The action of
partially permeable cell
membranes - selective diffusion and examples
Osmosis - examples and explanation
Some details of examples of osmotic action in individual animal or plant cell types
Osmosis experiments - demonstrations of osmotic action
with diffusion in liquids
Be able to draw particle pictures to
illustrate and explain diffusion in liquids.
Be able to describe and explain what diffusion is in liquids and
solutions using the kinetic particle model.
Know that the net migration of liquid or dissolved particles due to their
random motion is from a high concentration to a lower concentration.
Be able to interpret the simple experiment where potassium manganate
crystals dissolve in water and the coloured particles are observed to
diffuse and spread out throughout the liquid.
Be able to describe the importance of diffusion of dissolved substances
in and out of cells of living organisms by migration through the cell