Chemistry - Section 2

shorthand way of writing the name of a compound or element

chemical formula

diatomic elements

hydrogen - H2

nitrogen - N2

oxygen - O2

chlorine - Cl2

fluorine - F2

bromine - Br2

iodine - I2

writing formula - crossover rule

crossing over the valencies of each symbol

eg hydrogen sulfide = H2S

valency is the word

used to tell us how many bonds an atom of a particular element can make

when a formulae has meaningful names you must

ignore the valency

meaningful names

mon - 1

di - 2

tri - 3

tetra - 4

penta - 5

word equation

short hand way of describing a chemical reaction

the formulae never changes when balancing equations you

only add numbers infront of the symbols

a chemical reaction has taken place when

a new substance has been produced

filtration is a practical technique used to separate

an insoluble solid from a liquid

metals furthest left and down the groups are

most reactive

metals furthest right and up the groups are

least reactive

melting, boiling, freezing, condensing and dissolving are

not chemical reactions

toasting bread, growing hair/nails, height, foot rotting are

all chemical reactions

the quicker the products appear

the faster the rate of reaction

a fair test means

we must only change one variable at a fair time

a variable is any factor

controlled, changed or measured

eg -

concentration

particle size

temperature

mass

volume

for particles to react they

must collide

as concentration increases

rate of reaction also increases

as particle size decreases

rate of reaction increases

as the temperature increases

rate of reaction also increases

hydroxide contains

hydrogen and oxygen

cyanide contains

carbon and nitrogen

ammonium contains

nitrogen and hydrogen

a catalyst

speeds up the reaction without being used up

catalysts reduce

the energy that a reaction requires to take place

reaction

substances taking part in reaction

products

new substance thats produced