Chemistry A 1 Flashcards
How did Mendeleev arrange the elements
He put them in order of atomic mass but found he had to leave gaps for elements not yet discovered
Name three problems with Newlands law of octaves
His groups contained elements that didn’t have similar properties such as carbon and titanium
He mixed up metals and non metals such as oxygen and iron
He didn’t leave any gaps for undiscovered elements
How is the modern periodic table arranged
It is arranged based on electronic structure
List trends and properties within alkali metals (group 1)
As you go down group 1 they become more reactive and have lower melting and boiling points
They all have one outer electron
They form ionic compounds with non metals
Reacting them with water produces hydrogen gas
They are lithium sodium potassium rubidium caesium francium
List the trends and properties within the halogens (group 7)
As you go down group 7 the halogens become less reactive and have higher melting and boiling points
Halogens are all non metals with coloured vapours
Halogens from ionic bonds with metals
More reactive halogens will displace less reactive ones
List properties of transition metals
Good conductors of heat and electricity Dense, strong and shiny much more so than alkali metals Much less reactive that alkali metals Higher melting points than alkali metals They make good catalysts
What is hard water caused by and how is it different to soft water
Hard water is caused by lots of calcium and magnesium ions. It is different from soft water as when hard water is mixed with soap it produces scum. When heated it produces scale , which can eventually block heating pipes.
However it is healthy for teeth and bones and lowers the risk of heart disease
How does temporary hard water become soft?
Temporary hardness is removed by boiling the water
Describe treatment the process of water.
First it goes through a mesh screen to remove big bits such as sticks
Chemicals are then added to make solids and microbes stick together and fall to the bottom
Water is filtered through gravel beds to remove all solids.
Water is chlorinated to kill off any harmful microbes left
What is the downside to adding fluoride and chlorine to water
Fluorides can cause cancer and bone problems
Chlorine can produce toxic by products that can cause cancer
What is equilibrium and when does it occur
Equilibrium means that the amounts of reactants and products will reach a a certain balance and stay there.
It occurs when a reversible reaction takes place in a closed system
In what two ways can you move the position of the equilibrium to get more products and less reactants?
Changing the temperature and pressure
