Atoms and Elements
An element is made of only one type of atom.
Proton - +1
Neutron - 0
Electron - 1
35 - mass number (number of protons and neutrons)
17 - atomic number (number of protons - same as number of electrons)
Period Number (row)- number of shells
Group Number (column) - number of electrons on outer shell
Inner shell will only ever have 2 electrons!!!
E.g. Carbon will have two shells (period 2) and 4 electrons on outer shell (group 4)
Forms when atoms share pairs of electrons.
Conservation of Mass
Conservation of Mass:
Magnesium + Oxygen -> Magnesium Oxide
48g + ? -> 80g
80 - 48
Saturated fats have a single bond between their carbon bonds and tend to be solid at room temperature, e.g. lard. Unsaturated fats tend to be liquid at room temp.
Bromine Water Test on Fats:
Unsaturated fats contain double carbon-carbon bonds. They can be detected using bromine water.
Bromine water becomes colourless when shaken with unsaturated fats.
It stays orange-brown when shaken with saturated fats.
Limestone is mainly calcium carbonate.
Calcium Carbonate breaks down when heated strongly. This is called thermal decomposition.
Calcium carbonate -------heat---------> calcium oxide + carbon dioxide
Limestone, cement and mortar are all products of calcium carbonate. They slowly react with the carbon dioxide found in rainwater and wear away. This damages buildings/walls built of limestone.
Pollution from burning fossil fuel makes the rain more acidic than it should be, and this acid rain makes problems worse.
Advantages of Quarrying:
- Limestone is a valuable natural resource, used to make glass and concrete.
- Limestone quarrying provides employment opportunities that support the local economy.
Disadvatages of Quarrying:
- Limestone quarries are visible from long distances and may permanently disfigure the local environment. (Not aesthetically pleasing)
- Quarrying creates noise pollution, and heavy traffic that affects people's quality of life.
Metal ores are rocks containing a metal, or meta compound, in high enough concentration to make it economic to extract the metal. Ores are mined.
Iron is extracted from an iron ore in a blast furnace. Oxygen must be removed from the iron oxide to leave the iron behind. Reactions in which oxygen is removed are called reduction reactions.
Copper can be extracted from coper ores by heating them in a furnace. The copper is then purified during electrolysis.
Electrolysis: Electricity is passed through solutions containing copper compounds.During electroylsis, positively charged copper ions move towards the negative electrode and are deposited as copper metal.
Properties of metals are changed by adding other elements to it. A mixture of two or more elements, is called an alloy.
Seperating Crude Oil
Crude ol is a mixture of compounds called hydrocarbons (compounds that contain hydrogen and carbon atoms only, joined by covalent bonds). It can be seperated into different fractions called fractional distillation.
Sequence of events in distillation:
Heating ---> Evaporating ---> Cooling ---> Condensing
Fractional distillation is different from distillation in that it separates a mixture into a number of different parts, called fractions. A column is used, hot at the bottom an cool at the top. Substances with high boiling points condense at the bottom and substances with lower boiling points condense at the top.
Coal and crude oil are non-renewable. They take so long to form that they cannot be replaced once they have all been used up.
Biofuels are fuels produced from plant material. They have some advantages and disadvantages compared to fossil fuels.
- Increased income for farmers
- Biofuels limit the demand for fossil fuels, helping to reduce increases in fuel prices.
- Crops that could be used to feed people are used as raw materials for biofuels - food shortages?
- Potential food shortages could increase price of food.
Fractions that are produced by the distillation of crude oil can go through a process called cracking. Cracking is a chemical reaction which produces smaller, more useful hydrocarbon molecules, including alkanes and alkenes.
Fractions containing large hydrocarbon molecules are heated to vaporise them. They are then either:
- Passed over a hot catalyst
- Mixed with steam and heated to a high temp.
Alkenes contain a double covalent bond, which is shown as two lines between two of the carbon atoms. They is only one double bond in an alkene, no matter how many carbon atoms there are.
Alkenes can be used to make polymers. Polymers are large molecules made when many smaller molecules join together, end-to-end.
Examples of polymers and their uses:
PolymerTypical use polythene plastic bags and bottles polypropene crates and ropes polychloroethene
water pipes and insulation on electricity cables
Polymers are unreactive, which makes them suitable for storing food and chemicals safely. However, this property makes it difficult to dispose of polymers. They are usually sent to landfills.
Many polymers can be recycled. This reduces the disposal problems and the amount of crude oil used. But the different polymers must be seperated first, which can be difficult and expensive.
Earth's crust and upper part of the mantle are broken into large pieces called tectonic plates. These move at a few cms a year. This movement allows whole continents to shift = continental drift.
The plates move because of convection currents in the Earth's mantle. Driven by heat produced by the natural decay of radioactive elements in the Earth.
Wegener suggested that at one point, the world was one large continent. Over time, the single landmass began to crack and divide creating the seperated positions of the continents today.
Atmosphere: 78% Nitrogen, 21% Oxygen, 1% other gases.
Heat can be transferred from place to place by conduction, convection and radiation.
GOOD LUCK! :)