Biology - Diffusion

States of Matter.

The only states of matter diffusion can take place in are liquids and gases because unlike solids they have more kinetic energy and space to move.

What is a solvent?

a liquid in which particles are dissolved e.g water.

Selectively Permeable

a property of cell membranes that allows some substances to pass through, while others cannot.

What are solute ions?

particles in solution e.g. glucose, sodium ions, chloride ions.

Suggested ideas for practical work to develop skills and understanding.

-investigate how temperature affects the rate of diffusion of glucose through Visking tubing. -diffusion of ammonium hydroxide in a glass tube using litmus as the indicator. -observation of cells under a microscope, eg sprouting mung beans to show root hair cells.

give an example of when diffusion is used.

An example of where Diffusion is used, is in the body. It is used when o2 and CO2 are exchanged in the Alveolus.

what does the net movement mean?

An overall movement of particles from where there is a high concentration to where there is a low concentration.

Why is the rate of diffusion slower with larger molecules.

As they can not diffuse through the cell membrane and require more energy to move.

Suggest how the movement of carbon dioxide into the cells in maintained.

Carbon dioxide is used up inside the cell [1 mark] more/new carbon dioxide comes to the outside of the cell [1 mark]

Factors affecting diffusion.

Concentration gradient Temperature Distance Surface Area.

Give examples of diffusion in general.

Deodorant, Perfume, Smells when cooking, Making squash, Tea bag in water.

dissolved substances can move in or out of a cell by....

Diffusion

What is diffusion ?

Diffusion is the spreading of the particles of a gas, or of any substance in solution, resulting in a net movement from a region where they are of a higher concentration to a region with a lower concentration.

Why does Diffusion occur faster in higher temperature?

Diffusion occurs faster in higher temperatures because the speed of the particles rises, as does the temperature.

What type of substances can diffusion happen in?

Dissolved substances like liquids and gases.

What is the reason for diffusion taking place in dissolved substances like liquids and gases?

Due to the reason that the particles in these substances are free to move around randomly.

Temperature

Higher temperature means greater kinetic energy of particles and therefore diffusion happens faster

What is meant by concentration gradient?

Just another way of saying 'from high to low'.Molecules tend to move from areas of greater concentration to areas of lesser concentration i.e. "down the gradient"

What is a solution.

Mixture of 2 or more substances

concentration gradient

The difference between concentration. The greater the difference between concentration the faster the rate of diffusion therefore the steeper the concentration gradient.

What is the Diffusion gradient?

The diffusion gradient is the difference between two concentrations. When the gradient is bigger, diffusion will occur faster.

Distance.

The greater the distance the further the particles have to travel and the slower diffusion is.

Surface area

The greater the surface area the more surface there is where particles can diffuse and therefore the rate of diffusion is faster.

How do dissolved substances get into or out of cells?

To get into or out of cells, dissolved substances have to cross the cell membranes by diffusion.

Explain why diffusion is important for respiration.

When a cell is respiring the concentration of oxygen and glucose inside the cell is lower than the surrounding blood so these substances move into the cell.

Name the simplest type of diffusion.

When different gases diffuse through each other this is what's happening when the smell of perfume diffuses through the air in a room.

Oxygen required for respiration passes through cell membranes ......

by diffusion.

Do particles move down or up the concentration gradient during diffusion?

down

The larger the particles the....

slower the rate of diffusion.

greater the difference in concentration..

the faster the rate of diffusion.