Science Exam - fossil fuels

What is a hydrocarbon?

Crude oil is a mixture of substances which are mostly hydrocarbons. A hydrocarbon is a compound containing hydrogen and carbon only. Since crude oil is a mixture of different hydrocarbon compounds, the different hydrocarbons will have different boiling points. A sample of crude oil will therefore have a range of boiling points, and the mixture can be separated by fractional distillation.

What are the effects of burning fossil fuels on the environment?

1) Air pollution Burning fossil fuels produces waste products due to impurities in the fuel. It produces various gases, sulfur dioxide, nitrogen dioxide and volatile organic compounds. The result is acid rain, smog and soot. 2) Water pollution Water sources are contaminated from acid rain. Contaminated water affects plants, animal life and human beings. 3) Climate change The burning of fossil fuels contributes to the buildup of greenhouse gases, which is regarded as the leading factor in climate change and global warming. The detrimental consequences are a reduction in the ozone layer and warmer temperatures. A reduction in the ozone layer threatens human health, plant growth and the marine eco system.

What is the combustion of hydrocarbons?

Complete combustion happens when the hydrocarbon burns in an excess of air. Methane: The methane gas burns with a clear blue flame. methane + oxygen -> carbon dioxide + water + energy CH4(g) + 2O2(g) -> CO2(g) + 2H2O(l) = example of an EXOTHERMIC REACTION. Ethane: ethane + oxygen -> carbon dioxide + water + energy 2C2H6(g) + 7O2(g) -> 4CO2(g) + 6H2O(l) = The reaction is exothermic (gives out heat). The products are the same (carbon dioxide and water). More oxygen is required for the complete combustion of ethane

What is addition polymerization?

= A chemical reaction in which simple molecules (monomers) are added to each other to form long-chain molecules (polymers) without by-products. Atoms are not eliminated. The molecules of the monomer join together to form a polymeric product in which the molecular formula of the repeating unit is identical with that of the monomer. The molecular weight of the polymer so formed is thus the total of the molecular weights of all of the combined monomer units.

What is an addition polymer?

A polymer which is formed from monomers added together where no other substance is produced is called an addition polymer. Examples of addition polymers are: poly(ethene), poly(propene), poly(tetrafluoroethene), poly(chloroethene), and poly(phenylethene) -polystyrene.

What are alkanes and alkenes?

ALKANES - Mainly unreactive and used as fuels ALKENES - Much more reactive than alkanes because alkenes are UNSATURATED (they have a reactive double bond) - Starting material for many different chemicals. An alkene may be distinguished from an alkane by shaking the hydrocarbon with BROMINE WATER. -> Bromine water is brown or orange, and will lose its color when it reacts with a double bond in an alkene. -> Bromine water will stay brown with an alkane because an alkane has no double bonds.

What is the cracking of hydrocarbons?

After fractional distillation of crude oil there are too many large hydrocarbons and not enough small hydrocarbons to meet the public's demand. Some of the large hydrocarbons (the heavier fractions) are broken down into more useful smaller hydrocarbons (lighter fractions) by a process known as CRACKING. Cracking results in the formation of smaller, more useful alkanes (such as petrol), and even more useful alkenes (such as ethene). The fractions of crude oil consist almost entirely of alkanes. Cracking is the main source of alkenes

What are fossil fuels?

Fossil fuels come from the decay of plants or the animals which fed on them. There are three types of fossil fuels: coal, gas and crude oil. All of these are burned to produce heat. Fossil fuels are a finite resource and non-renewable. Fossil fuels are burnt in power stations to generate electricity.

What is the fractional distillation of crude oil?

Fractional distillation is the process of the separation of a mixture. 1) Crude oil is heated until it boils and then the hydrocarbon gases are entered into the bottom of the fractionating column. 2) As the gases go up the column the temperature decreases. 3) The hydrocarbon gases condense back into liquids and the fractions are removed from the sides of the column. The smaller the hydrocarbon molecule, the further it rises up the column before condensing. The fractionating column operates continuously.

What is the combustion of hydrocarbons?

Hydrocarbons are mainly used as fuels. -> The burning of a substance in air is called combustion. In chemistry, combustion (or burning) means reacting with oxygen. Therefore, combustion is a form of oxidation. COMPLETE COMBUSTION - In excess oxygen, hydrocarbons will burn to produce HEAT, CO2, AND WATER. ex. Methane + excess oxygen -> CO2 + water INCOMPLETE COMBUSTION - In insufficient oxygen, hydrocarbons will burn to produce HEAT, CARBON MONOXIDE GAS, SOLID CARBON, AND WATER ex. Excess methane + oxygen -> Carbon monoxide + water ex2. Excess methane + oxygen -> solid carbon + water Combustion of fossil fuels releases the energy which has been stored up in the plant and animal remains for millions of years.

What are examples of addition polymerization?

Polymerization of ETHINE: The double bond in an alkene (like ethene) can be broken open and joined to other molecules. A molecule of ethene can be joined to another molecule of ethene. In the process, the second ethene molecule has its double bond broken, and this may be added to a third molecule of ethene, and so on. Many ethene molecules can be joined together to form a polymer. The polymer is called poly(ethene) because it is made from ethene. Ethene put under pressure and heated with a catalyst will polymerise (make long chains of atoms) to form poly(ethene). Note that there are no double bonds in the polymer. Poly(ethene) is an alkane. It is a saturated hydrocarbon.

What is a polymer?

Polymers are very large molecules (sometimes called macromolecules). Each polymer molecule is a long chain of (mainly carbon) atoms. Polymers are made from many smaller molecules, called MONOMERS. These monomers (the starting materials) are often ALKENES. The general public know polymers as plastics. In science, the word plastic refers to a specific type of deformation. A polymer may show plasticity, or it may not. Call it a polymer, not a plastic. The process (chemical reaction) which turns monomers into polymers is called POLYMERIZATION. The conditions used for polymerisation are HEAT, PRESSURE, AND A CATALYST.

What are the properties of fractional distillation?

The different hydrocarbon fractions obtained from crude oil condense at different temperatures. The larger the hydrocarbon molecule... 1) The higher the condensing temperature (the higher the boiling point). 2) The more viscous it is (it takes longer to flow - like syrup). 3) The less volatile it is (it evaporates less quickly). 4) The less flammable it is (it does not set fire so easily).