Diffusion for Biology and Chemistry (IMPORTANTT!!!)

How do the particles move?

If molecules are left alone, they will move randomly in all direction and speed. Molecules bump into each other and change direction (rebound/deflect). Over time, they will are evenly spread out/distributed fairly overall due to their random motion.

Concentration

number of particles in a particular volume

When does diffusion stop?

when equilibrium is reached (concentrations are equal). However the movement of individual particles does not stop.

Factors that affect the rate of diffusion

- concentration gradient: the difference in concentration between two places

- temperature: particles gain energy and move faster

- size/mass of particles

- larger surface area

Which state of matter does diffusion take place?

Liquids and gases

Diffusion in fluids

Particles spread to fill the space available to them.

Particles can move freely and are in contact with one another.

- Particles move from a region of higher concentration toward a region of lower concentration; eventually the particles are evenly spread. Their concentration is the same throughout.

Which state of matter doesn't diffusion take place?

solids as the particles cannot move from one place to place

Dissolving

-Water around the crystal becomes purple as the solid dissolves.

- Particles move off from the surface of the crystal into the water.

- The crystal dissolves eventually.

- The purple color spreads throughout the liquid. Whole solution becomes purple.

-The particles from the solid become evenly spread through the water.

Diffusion in gases

Gases spread to fill the space available to them.

- Atoms/molecules move faster

- collide more frequently with other particles in the air and on the wall of the container

- Frequent collisions slow down the rate of diffusion.

- Pressure increases

What causes molecules to diffuse evenly

random movements of molecules

particles

the smallest pieces of which a substance is made; particles can be molecules, atoms or ions

kinetic energy

energy of moving particles

diffusion

The net movement of particles from a region of high concentration to a region of lower concentration/down the concentration gradient, as a result of their random movements (or) the process by which different fluids mix as a result of the random motions of their particles.

concentration gradient

an imaginary 'slope' from a high concentration to a lower concentration

net movement

overall or average movement