Additional Science OCR GCSE

Homeostasis :- Means mantaining a constant internal environment.

Negative feedback counteracts change keeping your internal environment the same.

Diffusion is the movement of particles from a region with high concentration to a region with a lower concentration.

Osmosis is the overall movement of water from a dilute to a more concentrated solution through a partially permeable membrane.

A partially permeable membrane only lets certain substances pass through it.

Enzymes are very specific proteins which speed up chemical reactions in cells.

Vasodilation occurs when body temperature is too hot, this is when blood vessels close to the skin surface increase in diameter.

Vasoconstriction occurs when body temperature is too cold, this is when blood vessels close to the skin surface decrease in diameter.

Atoms consist of the nucleus in the centre and electrons moving around it.

Proton = Mass 1 , Charge = +1, Neutron = Mass 1, Charge = 0 Electron = Mass 0.0005 , Charge = -1

Number of proton equal the number of electrons in an atom, if some electrons are added or taken away then it becomes on ion.

Electron Shell Rule:

1st shell =2 electons ,

2nd shell=8 electrons

3rd shell =8 electrons ...etc

Group 1 of the periodic table = alkali metals - become more reactive as you go down the table

Group 7 of the periodic table = Halogens - become less reactive as you go down the table

speed = distance /time or

momentum = mass x velocity

change of momentum = resultant force x time for which force acts

change in energy = work done

work done = force x distance

kinetic energy = 1/2 x mass x velocity