C3 - Chemicals in our Lives - Risks and Benefits Flashcards
What are the four layers of the Earth?
- Crust
- Mantle
- Outer core
- Inner core
tectonic plates
Massive portions of rock which make up the Earth’s surface
Convection currents
Small currents which move the tectonic plates around the earth
Name the ways the plates can move:
•By sliding past each other, colliding or pulling apart
Pangea
The supercontinent which all the continents used to be
Rocks
Raw materials found in the Earth’s crust
Name 3 important raw materials
Coal, salt and limestone
How is limestone made? 4 steps
- Shellfish died forming sediments on the sea bed
- Sediments compacted and hardened to form limestone, a sedimentary rock
- Tectonic plate movements pushed the rock to the surface
- Gradually the rocks above were eroded away until the limestone was exposed
How is coal made?
It is formed in wet, swampy conditions when plants like trees and ferns died and became buried. This excluded oxygen slowing decay.
How is salt made? 3 steps
- Rivers brought dissolved salts into the sea
- Climate warming evaporated the water, leaving salt that mixed with sand blown in by the wind
- Rock salt formed and was buried by other sediments
What evidence is there for the formations of limestone, coal and salt?
- Coal contains fossils of the plants that formed it
- Limestone contains bits of shell fragments from sea creature
- Rock salt contains different shaped water and wind eroded grains
- Ripple marks in rocks from water flow from rivers or waves in the sea
Two uses of salt
- Food
- As a source of chemicals
- To treat icy roads
What is salts chemical name?
Sodium chloride (NaCl)
How can salt be obtained?
- Collecting and evaporating sea water
* Mining underground deposits of rock salt
Why is rock salt spread on icy roads?
- The rock is insoluble but the sand in the rock salt gives grip
- It shows up so people know when roads have been gritted
- The salt in solution lowers the freezing point, preventing ice forming as easily
Where is Britain’s only salt mine?
Cheshire
Where can coal be sourced in the UK?
South Lancashire
Where can limestone be sourced in the UK?
The Peak District
How is solution mining carried out?
- Water is pumped at high pressure into the rock salt
- The salt dissolves
- The salt solution is pushed to the surface
Subsidence
When land collapses due to weak support underground
3 issues with solution mining:
- It causes subsidence
- It can allow water into mines which may let salt leach out into water supplies, contaminating them
- Evaporating salt from sea water takes up large areas and spreads salt into the local environment, damaging habitats
Two ways how salt is used in food
As a flavouring and a preservative
Three health problems which high salt intake can cause:
- High blood pressure
- Heart failure
- Strokes
Risk
The chance of getting ill and the consequences if you did
What do the DH and the DEFRA stand for and what do they do?
The Government department of health and the department of the environment, food and rural affairs are responsible for carrying out risk assessment for chemicals in food and advising the public about how food affects health.
Alkalis
Compounds which dissolve to give a solution with a pH higher than 7
Neutralisation
When alkalis neutralise acids to make salt
What is the word equation for neutralisation
Acid + Base (Hydroxide) -> Salt + Water
What are the uses of alkalis?
- Dyeing cloth
- Neutralising acidic soil
- Making soap
- Making glass
What substances were used in the past as sources of alkalis?
Stale urine and ash from burnt wood
What was soap made of?
Wood ashes, animal fat and water
What was neutral soil made of?
Seaweed, seaweed ashes and lime (calcium oxide)
Soda
Seaweed or seaweed ash
Lime
Calcium oxide
What is the actual chemical equation for limestone
Calcium carbonate
What was glass made of?
Lime, sand and seaweed
How was cloth dyed before?
Using plant dye and alum
Alum
Stale urine
Who discovered how to make an alkali in 1787?
Nicholas Leblanc
What did the Leblanc process do?
Made sodium carbonate by reacting salts and limestone heated with coal
What are the waste products of The Leblanc process?
Sodium carbonate, hydrogen chloride and galligu
What is problematics about hydrogen chloride and galligu?
Hydrogen chloride contributes towards acid gas and rain and Galligu slowly releases hydrogen sulphide a foul smelling, toxic gas
How is hydrogen chloride used?
- Chlorine used to bleach textiles
* Hydrogen acid which is a starting material for making other chemicals
What is the equation for making chlorine from Hydrochloric acid and manganese dioxide?
Hydrochloric acid + Manganese dioxide -> Chlorine + Manganese chloride + Water
Name 3 soluble hydroxides
Sodium hydroxide, potassium hydroxide and calcium hydroxide
Name 2 soluble carbonates
Sodium carbonate and potassium carbonate
Bases
Insoluble metal carbonates and metal hydroxide
Name 4 neutralisation equations:
Acid + Base -> Salt + Water
Acid + Metal Oxide -> Salt + Water
Acid + Metal Carbonate -> Salt + Water + Carbon dioxide
Acid + Metal -> Salt + Hydrogen
Why is chlorine added to water supply?
To kill microorganisms
What are the issues with using chlorine?
- Chlorine gas is toxic and can affect human health in excess
- Sone people disapprove of adding chlorine to water supplies. People using mains water supplies have no choice about chlorination
- Chlorine can react with organic materials in water supplies, forming toxic or carcinogenic compounds called disinfectant by products (DBPs)
Electrolysis
A process which breaks up compounds using an electrical current
What are the products of the electrolysis of brine?
Chlorine gas, hydrogen gas and sodium hydroxide solution
Anode
The positive electrode
Cathode
The negative electrode
At which electrodes do chlorine and hydrogen gases form
Chlorine at the anode and hydrogen at the cathode
What are each of the products of brine electrolysis used for?
- Chlorine for making plasticised PVC, in medicine and crop protection
- Hydrogen for making margarine, as rocket fuel and in fuel cells in vehicles
- Sodium hydroxide for paper recycling, industrial cleaners and refining aluminium
Risk assessment
A vigorous process which analyses the hazards and risks of a process
What four things do we need to know to decide the level of risk of a particular chemical?
- How much of it is needed to cause harm
- The chance of it escaping into the environment
- How much will be used
- Who or what it may affect
What is PVC
A plastic containing carbon, hydrogen and chlorine
Plasticisers
Small molecules added to plastics to make them softer
Uses of plasticised PVC
For covering electrical wires, clothing and seat covers
LCA
A life cycle assessment measures the energy used to make, use and dispose of a substance and it’s environmental impact
What are the four stages of an LCA?
- Preparing the chemical from raw materials found in plants, animals, rocks, the ocean or the air
- Making the product from the chemicals including transporting the chemicals and the finished product
- Using the product
- Disposing of the products and the materials in it when it is of no more use
What must be considered during an LCA?
- How much natural resources are required
- How much energy is needed or required
- How much water and air is used
- How is the environment affected
Geologists
Scientists which study rocks
