Key Concepts in Chemistry: Energy, Hydrocarbons, and Fuels

activation energy (Ea)

the minimum energy required by reactants in order to react

adsorption

the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface

alkanes

the family of hydrocarbons containing only single carbon-carbon bonds

alkenes

the family of hydrocarbons that contain at least one carbon-carbon double bond

amino acids

molecules that contain an amino and a carboxyl group

anaerobic respiration

the breakdown of glucose in the absence of oxygen

aquifer

an underground rock layer that contains water; this groundwater can be extracted using a well

biodiesel

a fuel produced from vegetable oil or animal fats and combined with an alcohol, usually methanol

bioethanol

ethanol produced from plants, such as sugarcane, and used as an alternative to petrol

biofuel

a renewable, carbon-based energy source formed in a short period of time from living matter

biogas

fuel produced from the fermentation of organic matter

carbohydrates

the general name for a large group of organic compounds occurring in food and living tissues; includes sugars, starch and cellulose

carbon neutral

no net release of carbon dioxide into the atmosphere

cellular respiration

the process that occurs in cells to oxidise glucose in the presence of oxygen to carbon dioxide, water and energy

cellulose

the most common carbohydrate and a condensation polymer of glucose; humans cannot hydrolyse cellulose, so it is not a source of energy

change in enthalpy

the amount of energy released or absorbed in a chemical reaction

chemical energetics

a branch of science that deals with the properties of energy and the way it is transformed in chemical reactions

chlorophyll

a series of green pigments that enable plants to capture sunlight for photosynthesis

climate change

changes in various measures of climate over a long period of time

coal

the world's most plentiful fossil fuel; it is formed from the combined effects of pressure, temperature, moisture and bacterial decay on vegetable matter over several hundred million years

Coldry Process

a patented process that changes the naturally porous form of brown coal to produce a dry, dense pellet, via a process called 'brown coal densification'

combustion

the rapid reaction of a compound with oxygen

cyclic hydrocarbons

also known as ring structures, because the carbon chain is a closed structure without open ends

dietary fibre

non-starch polysaccharides in both water-soluble and water-insoluble forms

dioxins

highly toxic compounds formed from industrial processes and incomplete combustion of organics

disaccharide

two sugar molecules (monosaccharides) bonded together

efficiency (of energy conversion)

the ratio between useful energy output and energy input

endothermic

describes a chemical reaction in which energy is absorbed from the surroundings

energy profile diagram

a graph or diagram that shows the energy changes involved in a reaction from the reactants through the intermediate stages to the products

enhanced greenhouse effect

the effect of increasing concentrations of greenhouse gases in the atmosphere as the result of human activity

enthalpy

a thermodynamic quantity equivalent to the total heat content of a system

ethanol

an alcohol with two carbons produced from fermentation of glucose by yeast

exothermic

describes a chemical reaction in which energy is released to the surroundings

fat

a triglyceride formed from glycerol and three fatty acids

fatty acids

long-chain carboxylic acids, usually containing an even number of 12-20 carbon atoms

feedstocks

raw materials used to supply or fuel a machine or industrial process

fossil fuels

fuels formed from once-living organisms

fracking

the process of pumping a large amount of fluid, mainly water, under high pressure into a drilled hole, in order to break rock so that it will release gas or oil

fractional distillation

the process of separating component fuels based on their different boiling points

fructose

a pentose monosaccharide

fuel

a substance that burns in air or oxygen to release useful energy

global warming

a gradual increase in the overall temperature of Earth's atmosphere

glycerol

an alcohol; it is a non-toxic, colourless, clear, odourless and viscous liquid that is sweet-tasting and has the semi-structural formula CH2OHCH(OH)CH2OH

greenhouse effect

a natural process that warms Earth's surface; when the Sun's energy reaches Earth's atmosphere, some of it is reflected back to space, and the rest is absorbed and re-radiated by greenhouse gases

greenhouse gases

gases that contribute to the greenhouse effect by absorbing infrared radiation

heat of reaction

the heat evolved or absorbed during a chemical reaction taking place under conditions of constant temperature and of either constant volume or, more often, constant pressure

hygroscopic

refers to when a substance has a tendency to absorb water vapour from the atmosphere

kerosene

a mixture of hydrocarbons with molecules containing between 10 and 15 carbon atoms

kilojoule

a unit of energy; one kilojoule (kJ) is equal to 1 × 10^3 joules (J)

kinetic energy

energy associated with movement, in doing work

lactic acid

an organic acid, C3H6O3, present in muscle tissue as a by-product of anaerobic respiration

legumes

plants that produce pods with a seed inside

lipids

substances such as fats, oils and waxes that are insoluble in water

liquefied petroleum gas (LPG)

a hydrocarbon fuel that consists mainly of propane and butane

megajoule

a unit of energy; one megajoule (MJ) is equal to 1 × 10^6 joules (J)

metabolism

the chemical processes that occur within a living organism to maintain life

monosaccharide

the simplest form of carbohydrate, consisting of one sugar molecule

natural gas

a source of alkanes (mainly methane) of low molecular mass

non-renewable

energy sources that are consumed faster than they are being formed

NOx

a term used for oxides of nitrogen, such as NO2 and NO, that contribute to air pollution

oxidation

loss of electrons; an increase in the oxidation number

particulates

solid and liquid particles small enough to be suspended in the atmosphere

petroleum

a viscous, oily liquid composed of crude oil and natural gas that was formed by geological processes acting on marine organisms over millions of years; it is a mixture of hydrocarbons used to manufacture other fuels and many other chemicals

photosynthesis

in the presence of light, carbon dioxide + water → glucose + oxygen

polysaccharide

more than ten monosaccharides bonded together

potential energy

energy that is stored, ready to do work

proteins

large molecules composed of one or more long chains of amino acids

renewable

energy sources that can be produced faster than they are used

secondary fuel

a fuel that is produced from another energy source

serving size

the recommended amount of food on a nutrition label for one serving

standard laboratory conditions (SLC)

100 kPa and 25 °C

starch

a condensation polymer of glucose

sustainable energy

energy that meets present needs without compromising the ability of future generations to meet their own needs

thermochemical equations

balanced stoichiometric chemical equations that include the enthalpy change

thermochemistry

the branch of chemistry concerned with the quantities of heat evolved or absorbed during chemical reactions

transesterification

the conversion of one ester (triglyceride) into another ester (biodiesel)

triglycerides

fats and oils formed by a condensation reaction between glycerol and three fatty acids

urea

a molecule synthesised in the liver to remove ammonia from the body

yeast

a single-celled fungus