Oils, earth and atmosphere summary

Oils, Earth and Oils, Earth and atmosphere summaryatmosphere summary

10 April 2023

Cracking hydrocarbonsCracking hydrocarbonsLarge hydrocarbon molecules are not

very useful. They can be cracked into smaller molecules by heating them and passing them over a catalyst.

The process of cracking involves thermal decomposition and produces some unsaturated hydrocarbons.

The test for unsaturated hydrocarbons is that they will turn red bromine solution colourless.

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Making polymers from Making polymers from alkanesalkanes• Plastics are long chain molecules

which are produced form unsaturated hydrocarbons.

• The small molecules used to create the long chains are called monomers.

• Once joined together the long chain is called a polymer.

• When a carbon to carbon double bond is broken and the molecules are linked we have an addition polymer.

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The properties of plasticsThe properties of plasticsThe forces between molecules are

called intermolecular forces. The strength of the force in a plastic depends on the monomer used to make the plastic.

If the force is weak the plastic softens when heated – these are called thermosoftening plastics.

If the force is strong the plastic does not soften when heated – these plastics are called themosetting plastics.

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New and useful polymersNew and useful polymersNew polymers are being developed

all the time – these designer plastics are made to perform in a specific way when used.

Certain polymers that respond to changes around them are called ‘smart polymers’ – they can regain their origins shape or respond to changes in light and temperature.

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Extracting vegetable oilsExtracting vegetable oilsPlants produce glucose during photosynthesis.

The glucose can then be changed into other chemical such as vegetable oils.

The vegetable oil can be extracted by crushing the plant material (like seeds) or by distillation.

Vegetable oils are more healthy than animal fats because they contain carbon-carbon double bonds – they are unsaturated.

The test for unsaturation is adding bromine water which turns colourless if the oil is unsaturated but remain orange if it is saturated.

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Cooking with vegetable oilsCooking with vegetable oilsThe boiling point of a liquid depends on the size of the

forces between molecules.The large size of vegetable oil molecules means that

these oils boil at a much higher temperature than water.

The texture of cooked food depends on the temperature at which it is cooked. So for example potatoes cooked in water and oil have very different textures.

Unsaturated oils melt and boil at lower temperatures than saturated fats.

Hydrogenating oils (adding hydrogen to them to remove the carbon-carbon double bond) results in higher melting points and the oil is said to be hardened.

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Everyday emulsionsEveryday emulsionsOil and water do not mix, however if

the oil droplets can be made very small and spread out throughout the liquid we have an emulsion.

In order to make an emulsion an agent which will attract both water and oil molecules is called an emusifier.

Emulsions made from vegetable oils include salad dressing and ice cream.

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Food additivesFood additivesChemicals are often added to foods for

the following reasons (1) to make it look more attractive (2) to preserve the food (3) to improve the texture (4) to control the acidity (pH) (5) to improve the flavour.Additives can be detected by using a

separating method such as chromatography or a mass spectrometer.

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Vegetable oils as fuelsVegetable oils as fuelsIt is now possible to make fuels from

vegetable material.Biodiesel can be made from vegetable

oils it is carbon neutral and free from sulphur however there is a huge need for food in the world so using oils in this way is not really a long term solution.

Ethanol can be made from sugar by allowing the sugar to ferment when yeast is added to the sugar solution.

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Structure of the EarthStructure of the EarthThe Earth has a

series of layers.The solid crust is

6km to 70km thick.

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The mantle behaves like a solid but does flow slowly, it is very thick – about 3000km.

The Earth’s core is made up of a mixture of iron and nickel – the outer layer is liquid and the inner layer is solid.

The restless EarthThe restless EarthThe Earth’s lithosphere (outer shell) is

cracked into a number of tectonic plates which are constantly moving.

The movement of the plates is caused by convection currents in the mantle. The mantle is semi liquid due to the heat produced by radioactive decay in the mantle.

Earthquakes and volcanoes occur where the tectonic plates meet. Earthquakes take place when the layers slip past each other but are difficult to predict.

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The tectonic platesThe tectonic plates12

The Earth’s past The Earth’s past atmosphereatmosphereThe Earth’s atmosphere was formed

originally by volcanic activity.The gases present were carbon

dioxide, methane and ammonia.As pants formed they consumed the

carbon dioxide and produced oxygen.

At the same time oxygen reacted with methane to form carbon dioxide and water vapour.

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The Earth’s current The Earth’s current atmosphereatmosphereThe ammonia reacted with oxygen

to form nitrogen and water vapour.The Earths present atmosphere

consists of 78% nitrogen, 21% oxygen, 0.9% argon (an inert noble gas) and 0.04% carbon dioxide.

The next slide shows how these changes took place over a long period of time.

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All positions are approximate

4500 million

Now3000 million

2000 million

1000 million

500 million

200 million

No gases

H2 and He

Volcanoes Algae Plants

CO2 NH3 CH4

O2 N2 H2O

The changing atmosphere

The Carbon Cycle

photosynthesis

eaten by

respirationrespiration

respiration

Death of plants

Death of animals and excretion

CO2 in air

Plants containcarbon compounds

Detritus feedersand microorganismsfeed on dead matter

Animals contain carboncompounds

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