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  • Created by: niki
  • Created on: 03-04-11 12:09

>we can split large hydrocarbon molecules up into smaller molecules by heating them and passing the gas over a catalyst

>cracking produces unsaturated hydrocarbons, which we call alkenes

>alkenes burn, and also react with bromine water producing colourless products

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cracking hydrocarbons

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> plastics are made of polymers

> polymers are large molecules made when monomers (small molecules) join together

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making polymers from alkenes

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> monomers affect the properties of the polymers that they produce

> changing reaction conditions can also change the type of polymer that is produced

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the properties of plastics

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> new polymers are being developed all the time. They are designed to have properties that make them specially suited for certain uses

> smart polymers may have their properties changed by light, temperature or other changes in their surroundings

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new and useful polymers

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> vegetable oils can be extracted from plants by pressing or distilation

> vegetable oils are important foods

> unsaturated oils contain carbon-carbon double bonds. We can detect them using bromine or iodine solution

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extracting vegetable oils

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> vegetable oils are useful in cooking because of their high boiling points

> vegetable oils are hardened by reacting them with hydrogen to increase their boiling and melting points (hydrogenation)

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cooking with vegetable oils

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> oils do not dissolve in water

> oils can be used to produce emulsions which have special properties

> emulsions made from vegetable oils are used in many foods, such as salad dressings and ice creams

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 everyday emulsions

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> additives may be added to food in order to improve it's appearance, taste and how long it will keep (it's shelf life)

>food scientist can analyse foods to identify additives

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what is added to our food

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e numbers

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> vegetable oils can be burned as fuels

> vegetable oils are a renewable source of energy that could be used to replace some fossil fuels

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vegetable oils as fuels

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> the earth consists of a series of layers

  • crust
  • mantle
  • outer core
  • inner core
  • centre of the earth

> scientists orignally thought that the features on the Earth's surface were caused as the crust cooled and shrank

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structure of the earth

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> the earth's lithosphere is cracked into a number of pieces (tectonic plates) which are constantly moving. Where these plates meet, earthquakes and volcanoes happen

> the motion of the tectonic plates is caused by convection currents in the mantle, due to radioactive decay

> earthquakes and volcanoes happen where tectonic plates meet. It is difficult to predict accurately when and where earthquakes will happen

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the restless earth

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> the earth's early atmosphere was formed by volcanic activity

> it probably consisted mainly of carbon dioxide. There may also have been water vapour together with traces of methane and ammonia

> as plants colonised the earth, the levels of oxygen in the atmosphere rose

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the earth's atmosphere in the past

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> the main gases in the earth's atmosphere are oxygen and nitrogen

> about four-fifths (4/5) (80%) of the atmospher is nitrogen and one-fifth (1/5) (20%) is oxygen

> the noble gases are unreactive gases found in group 0 of the periodic table. Their lack of reactivity makes them useful in many ways

> noble gases are helium, argon, neon, kyrpton, xenon and radon

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gases in the atosphere

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