Chemistry C1

Page 1

C1 1.1: Atoms, Elements and Compounds

Key Points

All substances are made up of atoms

Elements contain only one type of atom

Compounds contain more than one type of atom

An atom has tiny nucleus in its centre, surrounded by electrons.

C1 1.2: Atomic Structure

Key Points

Atoms are made of protons, neutrons and electrons

Protons and electrons have equal and opposite electric charges. Protons are positively charged, and electrons are negatively charged

Neurons have no electric chare. They are neutral

Atomic number = number of protons (=number of electrons)

Mass Number = number of protons + neutrons

Atoms are arranged in the periodic table in order of their atomic number.

C1 1.3: The Arrangement of Electrons in Atoms

Key Points

The electrons in an atom are arranged in energy levels or shells

Atoms with the same number of electrons in their outermost shell belong in the same group of the periodic table.

The number of electrons in the outermost shell of an element's atoms determines the way that element reacts.

The atoms of the unreactive noble gases (in Group 0) all have very stable arrangements of electrons.

C1 1.4: Forming Bonds

Key Points

When atoms from different elements react together they make compounds. The formula of a compound shows the number and type of atoms that have bonded together to make that compound.

When metals react with non-metals, charged particles called ions are formed.

Metal atoms form positively charged ions. Non-metal atoms form negatively charged ions. These oppositely charged ions attract each other in ionic bonding.

Atoms of non-metals bond to each other by sharing electrons. This is called covalent bonding.

C1 1.5: Chemical Equations

Key Points

As no new atoms are ever created or destroyed in a chemical reaction: The total mass of reactants = the total mass of products.

There is the same number of each type of atom on each side of balanced symbol equation.

C1 2.1: Limestone and its Uses

Key Points

Limestone is made mainly of calcium carbonate

Limestone is widely used in the building industry

The calcium carbonate in limestone breaks down when we heat it strongly to make calcium oxide and carbon dioxide. The reaction is called thermal decomposition.

C1 2.2: Reactions of Carbonates

Key Points

Carbonates react with dilute acid to form salt, water an carbon dioxide

Limewater turns cloudy in the test for carbon dioxide gas. A precipitate of insoluble calcium carbonate causes the cloudiness

Metal carbonates decompose on heating to form the metal oxide and carbon dioxide.

C1 2.3: The 'Limestone Reaction Cycle'

Key Points

When water is added to calcium oxide it produces calcium hydroxide

Calcium hydroxide is alkaline so it can be used to neutralise acids

The reactions of limestone and its products hat you need are shown in the 'limestone reaction cycle'.

C1 2.4: Cement and Concrete

Key Points

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 rocks or small stones called aggregate with water.

C1 2.5: Limestone Issues

Key Points

There are good and bad points about quarrying for limestone. For example, more jobs will be created but there will be a large scar on the landscape

Limestone, cement and concrete all have useful properties for use as building materials but the mining and processing of limestone and its products has a major effect on our environment.

C1 3.1: Extracting Metals

Key Points

A metal ore contains enough of the metal to make it economic to extract the metal. Ores are mined and might need to be concentrated before the metal is extracted and purified.

We can find gold and other unreactive metals in their native state

The reactivity series helps us decide the best way to extract a metal from its ore. The oxides of metals below carbon in the series can be reduced by carbon to give the metal element

Metals more reactive than carbon cannot be extracted from their ores using carbon.

C1 3.2: Iron and Steels

Key Points

We extract iron from iron ore by reducing it using carbon in a blast furnace

Pure iron is too soft for it to be very useful

Carefully controlled quantities of carbon and other elements are added to iron to make alloys of steel with different properties

Important examples of steels are:

low carbon steels which are easily shaped,

high carbon steels which are very hard,

stainless steels which are resistant to corrosion.

C1 3.3: Aluminium and Titanium

Key Point

Aluminium and titanium are useful because they resist corrosion

Aluminium requires the electrolysis of molten aluminium oxide to extract it as it is too reactive to reduce using carbon

Aluminium and titanium are expensive because extracting them from their ores involves many stages and requires large amounts of energy.

C1 3.4: Extracting Copper

Key Points

Most copper is extracted by smelting (roasting) copper-rich ores, although our limited supplies of ores are becoming more scarce

Copper can be extracted from copper solutions by electrolysis or by displacement using scrap iron. Electrolysis is also used to purify impure copper, e.g.. from smelting

Scientists are developing ways to extract copper that use low-grade copper ores. Bacteria are used in bioleaching and plants in phytomining.

C1 3.5: Useful Metals

Key Points

The transition metals are found in the central block of elements in the periodic table

Transition metals have properties that make them useful for building and making things. For example, copper is used in wiring because of its high electrical conductivity

Copper, gold and aluminium are all alloyed with other metals to make them harder.

C1 3.6: Metallic Issues

Key Points

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

Plants can remove metals from low-grade ores. The metals can be recovered by processing the ash from burning the plants

Recycling metals saves energy and our limited metal ores (and fossil fuels). The pollution from extracting metals is also reduced

There are drawbacks as well as benefits from the use of metals in structures.

C1 4.1: Fuels from Crude Oil

Key Points

Crude oil is a mixture of many different compounds

Many of the compounds in crude oil are hydrocarbons- they contain only hydrogen and carbon

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

C1 4.2: Fractional Distillation

Key Points

We separate crude oil into fractions using fractional distillation

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

Lighter fractions make better fuels as they ignite more easily and burn well, with cleaner (less smoky) flames.

C1 4.3: Burning Fuels

Key Points

When we burn hydrocarbon fuels in plenty of air the carbon and hydrogen in the fuel are completely oxidised. They produce carbon dioxide and water

Sulfur impurities in fuels burn to form sulfur dioxide which can cause acid rain

Changing the conditions in which we burn hydrocarbon fuels can change the products made

In insufficient oxygen, we get poisonous carbon monoxide gas formed. We can also get particulates of carbon (soot) and unburnt hydrocarbons, especially if the fuel is diesel

At the high temperatures in engines, nitrogen from the air reacts with oxygen to form nitrogen oxides. These cause breathing problems and can cause acid rain.

C1 4.4: Cleaner Fuels

Key Points

Burning fuels releases substances that spread throughout the atmosphere

Sulfur dioxide and nitrogen oxides dissolve in droplets of water in the air and react with oxygen, and then fall as acid rain

Carbon dioxide produced from burning fuels is a greenhouse gas. It absorbs energy which is lost from the surface of the Earth by radiation

The pollution produced by burning fuels may be reduced by treating the pollutants from combustion. This can remove substances like nitrogen oxides, sulfur dioxide and carbon monoxide

Sulfur can also be removed from fuels before we burn them to prevent sulfur dioxide gas being formed.

C1 4.5: Alternative Fuels

Key Points

Biofuels are a renewable source of energy that could be used to replace some fossil fuels

Biodiesel can be made from vegetable oils

There are advantages, and some disadvantages, in using biodiesel

Ethanol is also a biofuel as it can be made from the sugar in plants

Hydrogen is a potential fuel for the future.

c1 1.0: Fundemental ideas

C1 2.0: rocks and building materials

c1 3.0: METALS AND THEIR USES

C1 4.0: crude oil and fuels