Cracking hydrocarbons:
Hydrocarbon molecules can be broken down by heating them with steam to very high temperatures or by passing their vapours over a hot catalyst ( a substance that speeds up a chemical reaction. At the end of the reaction the catalyst remains chemically unchanged.)
Cracking produces alkenes and alkanes
Alkenes are unsaturated hydrocarbons and tun bromine water from orange to colouless

Making polymers from alkenes:
Plastics are made of polymers
They are large molecules made when many small molecules (monomers) join together
Alkenes can be used to make polymer such as poly(ethene) and poly(propene)

New and useful polymers:
New polymerws are being developed all the time
Polymers are designed to have properties that make them specially suited for certain uses: smart polymer is material used for stitching wounds that change shape when heated to body temperature

Plastic waste:
Non-biodegradable plastics cause waste, can harm wildlife and consume space in landfill sites
Biodegradable plastics are decomposed by the action of microorganisms in soil
Making plastics with starch granules in their structure helps the microorganisms break down a plastic, can be made from plan material such as cornstarch

Ethanol
Can be made by fermenting sugar using enzymes in yeast
Can also be made by hydration of ethene with steam in the presence of a catalyst, this process needs non-renewable crude oil whereas as fermentation uses renewable plant material

Plant Oils

Extracting vegetable oils
Vegetable oils can be extracted from seeds, nuts and fruits by pressing or by distillation
Vegetable oils provide nutrients and a lot of energy, they are important foods and can be used to make biofuels
Unsaturated oils contain C=C as so they decolourise bromine water

Cooking with vegetable oils
Vegetable oils are useful in cooking because of their high burning points
Cooking in oil increases the energy content of foods and changes the flavor, colour and texture of the food
Vegetable oils can be hardened by reacting them with hydrogen at 60c, as it makes them solids at room temperature which are suitable for spreading

Everyday emulsions
Oils do not dissolve in water but these two things can be used to produce emulsions which have special properties:opague and thick improves texture, appearance and their ability to coat and stick to solids
Emulsions made from vegetable oil are used for many foods: milk; cream; salad dressing; and, ice cream
Have molecules in which one part is hydrophilic and other hydrophobic

Food issues:
Vegetable oils are high in energy and provide nutrients, believed to better for health than saturated fats
Emulsifiers improve texture of foods enabling water and oil to mix, this makes fatty foods more palatable and tempting to eat

Our Changing Planet

Structure of the Earth
Earth is made of layers called the core, mantle and crust with the atmosphere around the outside
Earth's limited resources come from it's crust, the oceans and the atmosphere

The restless Earth
Earth's crust and upper mantle is cracked into tectonic plates which are constantly moving, these moves because of convection currents in the mantle that are caused by radioactive decay in the core
Earthquakes and volcanoes happen when tectonic plates meet, but is difficult to accurately predict when and where earthquakes will happen
Wagener's theory of continental drift was not accepted for years

Earth's atmosphere in the past
Earth's early atmosphere was formed by volcanic activity
Probably mainly consisted of carbon dioxide must have also been water vapour together with traces of methane and ammonia
As plants spread over the Earth, the levels of oxygen in the atmosphere increased

Life on Earth
Many theories of how life on earth started: compounds needed came from reactions involving hydrocarbons and ammonia when lightning provided energy
All the theories about how life started on Earth are unproven and so we cannot be sure how life began

Gases in the atmosphere
Most of the carbon dioxide in the early atmosphere became locked up in sedimentary rocks
About four-fifths almost 80% is nitrogen and about a fifth is oxygen 21%
Main gases in the air can be separated by fractional distillation these gases are used in industry as raw materials

Carbon dioxide in the atmosphere:
Carbon moves into and out of the atmosphere due to plants, animals the oceans and rocks
Amount of carbon dioxide in the Earth's atmosphere has risen in the recent past largely due to the amount fossil fuels we now burn

	Criado por Chima Power mais de 12 anos atrás

GCSE Chemistry Notas sobre Chemistry C1, criado por Chima Power em 01-02-2014.

Chemistry C1