Chemistry C1

Seite 1

Atoms, elements and compounds:

All substances are made of atoms

Elements are made of only one type of atom

Chemical symbols are used to represent atoms

Compounds contain more than more element

Atomic structure:

Nucleus of an atom is mad of protons and neutrons

Protons have positive charge, electrons a negative charge and neutrons not charged

Atomic number or proton number is equal to the number of protons in the nucleus of its atoms

Elements are arranged in order of their atomic number in the perodic table

mass number is the sum of the protons and neutrons in the nucleus of an atom

Arrangment of electrons

Atoms of unreactive noble gases all have very stable arrangements of electrons

Electrons in atoms are in energy levels that can be represented by shells

Electrons in the lowest energy level are in the shell closest to the nucleus

Electrons occupy the lowest levels first

All the elements in the same group of the perodic table have the same number of electrons in their highest energy level

Forming Bonds

compounds of metals bonded ton non-metals have ionic bonds

The formula of an ionic compounds shows the simplest ratio of ions

Compounds of non-metals have covalent bonds

Formula of a molecule shows the number of atoms in the molecule

Limestone and it's uses:

Mainly made of carbon carbonate

Used as a building material and to make cement and calcuim oxide

Cement mixed with sand, aggregate and water makes concrete

Calcuim carbonate decomposes when heated to make calcium oxide and carbon dioxide

Reactions of carbonates

Metal carbonates decompose when heated to produce metal oxide and carbon dioxide

carbonates react with acids to produce a salt,water and carbon dioxide

carbon dioxide turns limewater cloudy

The limestone reaction cycle

Thermal decomposition of calcuim carbonate produces calcuim oxide and carbon dioxide

calcuim oxide reacts with water to produce calcium hydroxide

Calcuim hydroxide is an alkali that can be used to neutralise acids

calcium hydroxide reacts with carbon dioxide to produce calcium carbonate

Cement and concrete

cement is made by heating limestone with clay in a kiln

Mortar is made by mixing cement and sand with water

concrete is made by mixing aggregate with cement, sand and water

Limestone issues

There are good and bad points about quarrying for limestone

Limestone, cement and concrete are needed as building materials

quarrying and processing limestone and it products have negative impacts on it's environment: dust and noise, more traffic, loss of habitats for wildlife, more customers and trade for local businesses, improved roads

Extracting metals:

Usually found in earth's crust, often chemically combined with other elements such as oxygen

Ore contains enough metal to make it worth extracting the metal

Unreactive metals are found in the Earth as the metal

Oxides of metals less reactive than carbon can be reduced using carbon

Iron and steels:

Iron oxide is reduced in a blast furnace to make iron, but is too brittle for many uses, many irons converted into alloys called steels which contains carefully controlled quantities of carbon and other elements

Auminium and titanium:

They both resist corrosion and have low densities when compared to other metals, both cannot be extracted by reduction both expensive because extracting involves many stages and requires large amounts of energy

Extracting copper:

Most copper is extracted from copper rich ores by smelting

Copper an be purified by electroloysis

Bioleaching and phytomining are new ways to extract copper from low grade ores

Copper can be obtained from solutions of copper salts by displacement or electrolysis

Useful metals:

Transition metals are found in the central block of the periodic table

Have properties that make them sutiable fro building and making things: good conductors of heat and electricity, strong but can be bent into shape

Most of the metals we use are alloys

Metallic issues

there are social, economic and environmental issues associated with exploiting metal ores

Recycling saves energy and limited resources

Drawbacks: obtaining ores causes pollution and uses limited resources, more expensive than other materials, iron and steel can rust

Benefits: They are strong, easily bent into shape (malleable), can be made into flexible wires (ductile) and good eletrical conductors

Fuels from crude oil:

Mixture of different compounds

Distillation can be used to seperate mixture of liquids

Most compounds in crude oil are hydrocarbons- they contain only hydrogen and carbon

Alkanes are saturated hydrocarbons as they contain as many hydrogen atoms as possible in their molecules

CnH2n+2 general formula

Fractional distallation:

Crude oil is separated into fractions using fractional distillation

The properties of each fraction depend on the size of the hydrocarbon molecules

Fractions with lower boiling points are less viscous(thick) and burn more easily (flammable)

Burning fuels:

Burning hydrocarbons in plenty of air produces carbon dioxide

While burning hydrocarbons in a limited supply of air produces carbon monoxide

Any sulfur compounds in fuel burn to make sulfur dioxide which makes acid rain

Oxides in nitrogen can be formed when fuels burn under extreme conditions

Cleaner fuels

Carbon dioxide causes global warming , many scientists believe

Particulates cause global dimming

Sulfur and nitrogen oxides cause acid rain

Pollutants can be removed from waste gases after the fuel is burned

Sulfur can be removed from fuels before they are burned so less sulfur dioxide is given off

Alternative fuels

Biodiesel can be made from vegetable oils

Biofuel are a renewable source of energy that could be used instead of fossil fuels

Advantages: contributes little to carbon dioxide levels carbon neutral

Disadvantages; growing use large areas of farmland

Ethanol made from sugar is a biofuel

Hydrogen is a potential fuel for the future

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

Fundematal ideas

Rocks and building Materials

Metals and their uses

Crude oil and fuels

Products from oil