Chemicals in our lives Flashcards
Who studies rocks?
Geologists
What do geologists learn from rocks?
How rocks form, how they change, how and when changes happen.
What are the chunks of the earth’s crust that move called?
Tectonic plates
How do tectonic plates interact?
Slide past each other, collide or pull apart
What builds mountains?
Plate collisions.
How can geologists explain the past history of the earth?
By observing what happens today and assuming that would have happened in the past.
Has Britain always been where it is now (on the earth’s globe)?
No, it has drifted over the years.
Where was Britain 600 million years ago?
Near the south pole - and we had an ocean between England and Scotland
What happened to the different continents as the drifted?
They all crashed together to form a supercontinent
What was the supercontinent called?
Pangea
What sort of rock is formed when lava cools?
Igneous.
What happens to the magnetic materials in lava in the earth’s magnetic field?
They line up with the magnetic field.
What happens to the magnetic field of the earth over time?
It changes.
How do igneous rocks support the theory of continental drift?
The magnetic fields are not lined up with the current poles, and show slow progression over time.
What are rocks, from an industrial point of view?
Raw materials buried in the ground.
Give some examples of rocks used as raw materials.
Coal, salt, limestone. (Salt = NaCl, limestone = CaCO3)
How is limestone formed?
Sea creatures die and their skeletons form sediment. Sedimentary rocks form, pushed to the surface by plate tectonic movements.
How is coal formed?
Trees and other plants die and are covered by a swamp, where the low oxygen makes decay very slow. Pressure eventually makes coal.
How are salt deposits formed?
Rivers wash it to the sea or lakes, then evaporation leaves it behind, it gets buried by other sediments.
Salt is found in Cheshire. What does this tell you about the history of Cheshire?
It was covered by a shallow sea.
What evidence is there for our theory of how coal is formed?
Fossils of plants found in coal
What evidence is there for our theory of how limestone is formed?
Limestone contains bits of sea creatures and shells.
What evidence is there for our theory of rock salt formation?
Rock salt contains different shaped grains that show water erosion and wind erosion.
What is salt used for?
The food industry; as a source of chemicals (sodium and chlorine); to put on roads in winter.
How can we obtain salt?
Evaporation of sea water; mining salt deposits.
What is the chemical formula for salt?
NaCl
Why is rock salt used for spreading on roads?
Sand in rock salt gives grip; sand is easily visible so it is easy to see where the salt is; salt in solution lowers the freezing point of water.
How many rock salt mines in the UK?
One, in Cheshire.
Where would you choose to extract salt from sea water?
In hot countries, it is not economical in the UK
What could happen if you extract all the salt in a specific part of the mine?
Subsidence
What can be done to reduce the risk of subsidence?
Leave salt behind to hold the rocks up - about half is currently left.
How, other than digging, can salt be mined?
Solution mining
How does solution mining work?
Pump high pressure water into the mine, it dissolves the salt and brine comes up.
What is the advantage of solution mining?
automatic; leaves the sand behind and produces purer salt
What is the risk of mining salt?
If water gets into the mine it can dissolve salt and that could contaminate the water supply
Why is salt added to food?
flavour; preserves food
How does salt preserve food?
It draws water out of living things by osmosis.
What are the health implications of too much salt?
It is bad for health.
What health problems can salt cause?
high blood pressure; heart failure; strokes
What is salt classified as?
A hazard.
What is the (health) definition of risk?
The chance of getting ill, and the consequence if you did.
How can the risk associated with eating salt be estimated?
By measuring salt intake.
How can you know how much salt is in a food product?
The label has to show how much salt is in it.
What does knowing the risk allow you to do?
Make informed decisions.
What is the word equation for neutralisation?
Acid + base => salt + water
What is an alkali?
A soluble base, which has to have a pH of over 7
What are alkalis used for in industry?
Dyeing cloth; neutralising acid soil; making soap; making glass
What was used as an early alkali?
Stale urine, ashes from burning wood.
What was the first alkali to be manufactured?
lime - Calcium oxide, CaO
How was Calcium Oxide produced?
Heating limestone (Calcium carbonate)
What is the chemical equation for heating limestone?
CaCO3 => CaO + CO2
Who discovered a way of making sodium carbonate?
Leblanc
What is the Leblanc process?
Heating salt and limestone
What by-products does the Leblanc process make?
Hydrogen chloride ( HCl), and solid waste that released hydrogen sulfide
What is the HCl used for now?
Making hydrochloric acid; making chlorine
How can you make chlorine?
By reacting manganese dioxide and hydrochloric acid
Name some alkalis
NaOH, KOH, Ca(OH)2, Na2CO3
What happens when a metal hydroxide reacts with acid?
hydroxide + acid => salt +water
What happens when a metal carbonate reacts with acid?
carbonate + acid => salt + water + CO2
What happens when you react Ionium hydroxide with Gabic acid?
hydroxide + acid => salt and water. In this case, the salt would be Ionium gabate.
Why is chlorine added to drinking water?
To kill microorganisms
Before chlorination of drinking water, what happened to people drinking the water?
Many died.
What exists between the start of water chlorination in the US and a fall in death rates from typhoid?
A correlation
What is chlorine?
A toxic gas. Group 7, very reactive.
What would happen if too much chlorine were added to the drinking water?
It would affect human health. Chlorine was used to “gas” soldiers in WW I
What choice do you have about chlorine in the mains water?
None, but you could drink bottled water or use a carbon filter to remove it (like our fridge)
Why are people worried about chlorine in the drinking water?
It can react with organic materials in the water supply to form toxic/carcinogenic compounds called disinfectant by-products
What is electrolysis?
Breaking up a compound by use of an electric current
What are the products of the electrolysis of brine?
Hydrogen (H2) ; Chlorine (Cl2); Sodium Hydroxide (NaOH)
Which electrode is the cathode?
The negative electrode - so it attracts the cations, the positive ions.
Which electrode is the anode?
The positive electrode - so it attracts the anions, the negative ions.
Why is electrolysis expensive?
It uses a lot of electricity.
Why are the advantages of the electrolysis of brine?
Cheap raw material; all the products are useful
What is brine?
Sodium chloride in solution.
When brine is electrolysed, what forms at the cathode?
Hydrogen (H2)
When brine is electrolysed, what forms at the anode?
Chlorine (Cl2)
What colour would sodium hydroxide solution turn litmus paper?
Blue or violet - it is alkaline
What is the industrial use of chlorine?
Plastics such as PVC (polyvinylchloride), in medicine, crop protection
What is the industrial use of hydrogen?
Making margarine and other hydrogenated fats (bad for health!); rocket fuel; fuel cells in cars being worked on
What is the industrial use of sodium hydroxide?
Paper recycling; industrial cleaners (and domestic drain unblockers); aluminium refining.
Why is brine electrolysis such a widely used industrial process, despite the cost of the electricity?
It produces three chemicals that are very useful, and common salt and water are cheap.
Why have some chlorine products been banned from fridges?
They damage the ozone layer - CFCs - no longer permitted in fridges.
Why is chlorine being used to bleach paper a problem?
It produced dioxins, very dangerous chemicals that have been shown to increase the risk of cancer.
Why would using a mercury diaphragm method to be able to do continuous electrolysis be a problem?
It releases mercury waste. Mercury salts build up in the tissues of living things, so mercury is a cumulative poison.
What is the problem with plastics made using chlorine?
They are not biodegradable
What do chemicals contain?
Elements.
How can you destroy an element (chemistry)?
You can’t, so the elements stay in the environment forever.
How do you work out how dangerous a substance is?
A risk assessment.
What are the states of matter?
Solid; liquid; gas
When toxic chemicals persist in the environment, what can happen?
They can be carried large distances, enter food chains, and build up in the tissues of living things.
What do you need to know to decide the level of risk posed by a chemical?
How much is needed to cause harm; how much will be used; the chance of it being released into the environment; what the effects would be
When were European laws passed making risk assessments compulsory for new chemicals?
30 years ago
What risk assessments have been done on substances used before then?
Could be none.
Why do people perceive new chemicals as more risky?
They have unfamiliar names, and people often assume that older substances will have been thoroughly tested by now, which may not be the case.
What does PVC contain?
it is a polymer containing carbon, hydrogen and chlorine.
Why are plasticisers added to PVC?
To soften it, to make it suitable for electrical cables and rain coats.
What is the size of the plasticiser molecule?
Small
What happens to the plasticisers over time?
They can leach out of the plastic, so old plastic is often very brittle.
What are the safety worries about plasticiser molecules?
The plasticisers have been tested, but they may affect fish, and large amounts do harm animals.
What has plasticised PVC been banned from being used for?
Children’s toys (Europe and USA) - fake toys may contain it.
What does PVC give off when burned?
Toxic gases including dioxins
What happens to dioxins?
If they enter the food chain they build up in fat and are thought to cause cancer.
Why are people disputing the safety of plasticisers?
They are new, so no long-term safety tests have been conducted.
What is an LCA?
A Life cycle assessment.
What does an LCA measure?
The energy used to make, use and dispose of a substance.
What are the 4 stages of an LCA?
Preparing the chemicals from raw materials; making the product, including transport; use of the product; disposing of the product when it is no longer used.
What is considered at each stage of an LCA?
What resources required; how much energy needed (or produced); how much water and air used; how is the environment affected.
What does doing LCAs enable you to do?
Compare different products fairly
What do you need for an accurate LCA?
A lot of data!
Why are some aspects of the LCA so hard to measure?
The use and disposal of a product can vary so much - a car may crash and be written off after one hour, or still be used 25 years later.
