The Movement of Molecules
Molecules are always moving.
- When we measure temperature, we are actually
measuring the speed of the molecules.
- The higher the temperature the faster the
movement of the molecules.
- The movement of molecules is
random.
Concentration
- Concentration is the amount of something in a
given volume.
- The formula is
- Box A has a higher concentration of particles
than Box B
Diffusion
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- Diffusion is the movement of molecules from
high to low concentration under their own power.
- Because there are more molecules on the left
there is a greater chance that their random movement will result
in more molecules moving to the right
- Eventually the molecules will be evenly spaced
and the whole box will be at the same concentration .
- Because the molecules continue to move
randomly, as one leaves an area another will replace
it.
Semipermeable
Membrane
- A membrane that will not let all molecules
through it is called a semipermeable membrane. Molecules that are
too large to fit through the membrane's pores can not pass through
it. A cell membrane is a good example of a semipermeable
membrane.
Osmosis
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- Osmosis is the diffusion of water molecules
through a semipermeable membrane.
- Here the water molecules will enter the cell
by the process of osmosis.
- They are going from high to low concentration
through a semipermeable membrane.
Passive
Transport
- Passive transport is the movement of molecules
into or out of a cell by the processes of diffusion and
osmosis. Since the cell does no work the cell is
passive.
Active
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- Active transport is when the cell moves
molecules from low concentration to high concentration. Since the
cell must do work and use energy the cell is active.