What are the three m ost important raw materials in the earths crust?
formed when shellfishdied forming sediment on the sea floor
hardened to form limestone
movement of the tectonic plates pushes rock to the surface
rock eroded away showing limestone
-formed by ancient ferns were compressed without oxygen,leaving coal
-rivers bring dissolved salts into the sea
- climate change evaporated the water, leaving salt that mixed with sand, which was blown by the wind
rock salt formed and was buried under sediment
ripples in the rock indicate water was present
What the three methods of salt extraction?
1. Evaporation of sea water
can be evaporated under the Sun
leaves salt cyrstals
needs large area and may spread salt into the local habitat
2. Solution Mining
- water pumped in the mine
salt dissolves to form a brine
brine transported away
-pure,yet can cause structural frailties to the land
-mining rock salt
- inefficient and lacks purity
much salt needs to be left in the mines as support
What is salt?
Why is salt used as grit?
As it lowers the freezing point of ice, making it melt
What is salt used for?
prevents bacterial growth
used in chemical experiments
Why is too much salt bad for your health?
Salt may cause increased blood pressure and even heart attacks or strokes
can be classified asa hazard
What is a neutralisation reaction/
What are alkalis uesd for?
Neutralising acidic soil
making soap and glass
What was the original alkalis?
stale urine and burnt ash
seaweed also, which was used to neutralise acidic soil
What was the first industrail alkali?
Made by heating lime in a kilm
Used when removing impurities from iron
making glass and neutralising soil
Who discovered how to make an alkali?
1787 frenchman Nicholas Leblanc
What was leblanc's process and what were some of the issues?
proces was to make sodium carbonate by reacting salt with limestone
gave off large amounts of hydrogen chloride(acidic gas) pollutant
also released hydogen sulfide
later hydrogen was converted into chlorine and hydorchloric acid
How can chlorine be produced from hydrogen chloride?
Reacting it with maganses oxide
oxidation converts hydrogen chloride into chlorine
What are some reactions involving acids?
Hydroxide+ acid produces salt and water
Carbonate+ acid produces salt+water+carbon dioxide
What are the riska and benefits of using clorine in drinking water?
destroyed typhoid and cholera in water
A toxic gas
used in wars
can react with organic materials to form toxic and catcinogenic compounds
positives outway the risks
What is electrolysis?
This where an anode(positive electrode) and a cathode(negative electrode)
attract the free positive and negative ions iun the water
it can be used to make chlorine and hydrogen gas
What bare the uses of chlorine and hydrogen gas and sodium hydroxide?
-Chlorine for making plastics like PVC, medicine , crop protection
- hydrogen= margarins, rocket fuel, fuel cells
sodium hydroxide - used in paper recycling, industrial cleaners, refining aluminium
What are the environmental impacts of chlorine products
- chlorine in fridges and aerosals are non recyclable
linked to ozone depletion
chlorine in paper bleaching, releases dioxins- cancer risk
Is PVC dangerous?
plasticised PVC used in electrical wires
-plasticiser molecules can be leached out and caused harmful effects
PVC toys banned in Europe and USA
-gives off dioxins when burnt- cancer risk
What is the Life Cycle Assesement?
measures energy used to make and dispose a substance and its environmental impacts
1. How much natural resources are required?
2.How much energy is needed or produced?
3.How much water and air is used
4. how is the environment affected
requires lots of data
has limitations, cars can be disposed differently