C3 - Chemicals in our Lives

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Flashcards by franimal, updated more than 1 year ago
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Created by franimal about 8 years ago
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Cambridge IGCSE Chemistry Flashcards on C3 - Chemicals in our Lives, created by franimal on 10/29/2013.

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Question Answer
How do we found out how a country has moved over hundreds of millions of years? Magnetite cools in the direction of the Earth's magnetic field. The further the rock was from the equator, the bigger the angle of the magnetite.
How do fossils help geologists studying past environments? Their characteristics help geologists work out the conditions - eg a giraffe has a long neck because trees have high leaves.
How do fossils help geologists date rock layers? Fossils are often distinctive to certain time periods.
What is salt used for? (3 reasons) Preserving and flavouring food, chemicals such as chlorine and applying to roads.
Name but don't describe the three methods for extracting salt. Evaporating it from sea water, mining it from rock and using solution mining.
Describe sea salt evaporation and what it's used for. The sun evaporates sea water from shallow pits, leaving the salt to be scraped up. It's used for food.
What is and what is the use of solution mining? Water is pumped into the rock where the salt, but not impurities like clay, dissolves. The water is evaporated and the salt used in the chemical industry.
Describe rock mining and its uses. Highly impure salt is mined out by machines. It's spread on roads because salty water has a lower freezing point.
What is the salt used in food? Sodium chloride
What are the health risks associated with eating more than 6g of salt per day? High blood pressure, leading to heart attacks and strokes.
Describe three properties of alkalis. Compounds that dissolve in water to form a solution with a pH higher than 7. Can be neutralised with acid to form a salt. Solution have hydroxide ions.
alkaline hydroxide + acid = ? = salt + water
alkaline carbonate + acid = ? = salt + water + carbon dioxide
What was the Leblanc process? A highly polluting way of making alkalis used in Victorian times.
Why is chlorine added to water? It kills microorganisms that live in water, saving millions of lives.
What are THM's? THM's can form when chlorine reacts with organic material such as leaves. There is an unproven theory that their consumption causes cancer.
What is brine? A solution of sodium chloride (NaCl) dissolved in water (H20). Otherwise known as salty water.
What is electrolysis? The process of splitting up a chemical into its elements by passing an electric current through it.
What happens in the electrolysis of brine? The solution splits into sodium chloride and sodium hydroxide, with chlorine and hydrogen gas bubbling off separately.
What are the environmental worries over electrolysis? It needs masses of energy, mostly from fossil fuels, and it used to use mercury which is highly toxic.
Why are synthetic chemicals that aren't safe still in use? Because there is no evidence that in tiny, tiny doses they're unsafe.
What are POP's? Persistent organic pollutants - they don't break down but can build up in fatty tissue. They're banned in many countries.
DDT is a powerful, mosquito killing pesticide. Why do some countries still use it? The risk of malaria killing you is much higher than the risk of DDT killing you in these countries.
What is PVC? A synthetic polymer that is strong, easy to use and relatively cheap.
What are the two raw materials for PVC, and what do they make? Ethene and chlorine are combined to make vinyl chloride.
Describe vinyl chloride and how it's made into PVC. A cancer-causing liquid made up of small molecules. Polymerisation is used to join the monomers into a polymer.
Describe how PVC can be recycled and why it's often difficult. It's ground into pellets and remoulded, but often PVC is mixed with other materials, making recycling costly.
What is energy recovery? What are the risks? The process of burning PVC in incinerators to produce electricity. Can very easily lead to hazardous chemicals being released.
What are phthalates? The most common plasticisers for PVC.
Why are some people worried about plasticisers? What are the two big examples? They can dissolve in liquids, and so get into baby's saliva from toys or into patients blood from blood bags.
What is DEHP? A plasticiser banned from toys because it MIGHT cause infertility.
Why is DEHP still used in medical equipment? The risk of not treating ill people is much, much higher than the risk of exposure to DEHP. There are no viable alternatives.
What is a life cycle assessment? The LCA is a piece of legislation designed to protect the environment. It collects data to see how big the environmental impact will be.
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