The smallest part of an element that can exist
An arrangement of all the elements based on their atomic number
Compounds are formed from elements by chemical reactions
Chemical reactions always involve the formation of one or more new substances and often involve a detectable change in energy (e.g. temperature change).
Compounds contain two or more elements chemically combined in fixed proportions.
Compounds can only be separated into elements by chemical reactions.
A mixture consists of two or more elements or compounds not chemically combined together.
Filtration, crystallisation, simple distillation, fractional distillation and chromatography.
Filtration, evaporation and crystallisation.
New experimental evidence.
Tiny spheres that could not be divided.
Thomson described the “plum pudding” model where a ball of positive charge is embedded with negatively charged electrons
Alpha particles (helium nuclei) were fired at a thin gold sheet. If the “plum pudding” was correct the alpha particles would pass straight through.
Although most of the alpha particles passed through some were deflected and a few even bounced back.
Rutherford concluded that the mass of the atom was concentrated at the centre in a nucleus.
Bohr suggested that the electrons orbit the nucleus at specific distances.
The number of electrons in an atom is equal to the number of protons.
Atoms are neutral.
The number of protons in the atom.
Light microscopes allowed for the discovery of cells and electron microscopes allowed for the discovery of organelles within the cell.
electron microscopes have high magnification and high resolution (detail). Light microscopes have low resolution and low magnification.
Almost all the mass is in the nucleus.
The sum of the protons and the neutrons.
Atoms of the same element which have the same number of protons but different numbers of neutrons
Protons: 1, Electrons: 1, Neutrons: 0.
Protons: 3, Electrons: 3, Neutrons: 4.
Protons: 6, Electrons: 6, Neutrons: 6.
Protons: 19, Electrons: 19, Neutrons: 20.
Protons: 92, Electrons: 92, Neutrons: 146.
It is the average atomic mass that takes into account the abundance of isotopes of the element.
(Abundance of isotope 1 x atomic mass of isotope 1) + (Abundance of isotope 2 x atomic mass of isotope 2) / 100.
The innermost shell.
The electrons occupy the lowest available energy shells (inside shells to outside shells).
The number of electrons in the outer shell gives the group number. The number of shells is the period. Chlorine has 7 electrons in its outer shell so it is found in group 7. Chlorine has electrons in 3 shells so it is found in period 3.
They are arranged by atomic number.
Elements with similar properties are arranged in groups.
Because similar properties occur at regular intervals.
Because they have the same number of electrons in their outer shell.
By atomic weight.
He organised the elements by atomic weight and by similar properties.
For undiscovered elements.
The discovery of isotopes.
To the left and towards the bottom.
To the right and towards the top.
Malleable is the ability the bend and hammer metal.
Conductors of heat, conductors of electricity, High melting and boiling points, shiny, usually solid at room temperature.
The substance will shatter if struck.
Generally do not conduct electricity, Are not always solid at room temperature, often have a lower density, dull
Metals usually have only a few electrons in the outer shell. It is easier for them to lose electrons to get a full outer shell.
Non metals usually have more electrons in their outer shell. It is easier for them to gain electrons or share electrons to get a full outer shell.
The noble gases.
Elements in group 0 are unreactive.
Elements in group 0 have 8 electrons in their outer shell except helium which has 2 electrons.
The boiling point of group 0 increases as you go down the group (increase atomic mass).
The alkali metals.
Lithium hydroxide + hydrogen.
The reactivity increases as you go down the group (increase atomic mass).
Reactions occur because of the electrons in the outer shell. As you go down the group the electron shells increase. The further away the outer electron is from the nucleus, the easier it is to lose.
They are non-metals and they form molecules made from two atoms e.g. Cl2.
Fluorine and chlorine.
Iodine and Astatine (technically you could say tennessine, but only six atoms have ever existed)!
Halogens form ionic compounds when they react with metals
Halogens form simple covalent compounds when they react with non-metals.
As you go down the group (increase the atomic mass) the melting point and boiling point increases
The reactivity decrease as you go down the group (increase atomic mass).
Reactions occur because of the electrons in the outer shell. As you go down the group the electron shells increase. The further away the outer shell is from the nucleus, the harder it is to attract an extra electron.
A displacement reaction will occur where the more reactive halogen will displace the least reactive halogen and bind with the salt.
Cl2 + 2KI → 2KCl + I2
I2 + KBr → I2 + KBr (no reaction because Iodine is less reactive than bromine)
F2 + 2KCl → 2KF + Cl2
Ionic, covalent and metallic.
Electrons are either donated or received.
Electrons are shared.
Outer shell electrons are delocalised.
Electrons in the outer shell of the metal atom are transferred
Positively charged ions.
Negatively charged ions.
The ions have the electronic structure of a noble gas (group 0)
A giant structure of ions
Ionic structures are held in place by strong electrostatic forces of attraction between oppositely charged ions.
They are formed when two non metals share electrons.
Ammonia, water, methane or hydrogen chloride.
Diamond and silicon dioxide.
poly(ethene). A polymer
Metals consist of giant structures of atoms arranged in a regular pattern.
Outer shell electrons of metal atoms which are free to move through the whole structure.
The sharing of delocalised electrons gives rise to strong metallic bonds.
Solid, liquid and gas.
Particles are close together in fixed positions and form a regular structure. There are strong forces of attraction between the particles. The particles vibrate in position.
Particles are close together but can move over each other. There are weak forces of attraction between the particles. The particles are constantly moving.
Particles are far apart. There are very weak forces of attraction between the particles. Particles move constantly in straight lines.
Atoms themselves do not have the bulk properties of materials
Particle theory represents particles as solid, inelastic spheres which have no forces between them.
The energy required to change state depends on the strength of forces between the particles.
The stronger the forces between the particles the higher the melting and boiling points.
Ionic compounds have regular structures called giant ionic lattices. The are strong forces of attraction between oppositely charged ions.
Ionic compounds have high melting points and boiling points because a large amount of energy is required to break the multitude of strong bonds.
The ionic compounds will conduct electricity.
Small molecules are usually gases or liquids which have low melting and boiling points.
Weak intermolecular forces.
The weak intermolecular forces between the molecules are broken, not the covalent bonds between the atoms.
A single unit of a polymer.
Polymers are very large molecules made of repeating units.
Strong covalent bonds link the atoms together in polymers.
The intermolecular forces between polymers are relatively strong so polymers are usually solids at room temperature.
The atoms are in the structures are linked to other atoms by strong covalent bonds
They are solids with high melting points.
Diamond, graphite and silicon dioxide (silica)
An alloy is a mixture of metals e.g. 18 carat gold is a mixture of gold and silver.
Giant structures of atoms with strong metallic bonding.
Metals are usually solid at room temperature and have high melting points and boiling points.
Atoms in metals are arranged in layers. These layers can slide over each other.
Metals can be bent and shaped.
Alloys are harder because the mixture of metal atoms causes a distortion of the layers which prevents them sliding easily over each other.
Delocalised electrons carry charge through the metal.
Delocalised electrons transfer energy through the metal.
A giant covalent structure
Very hard, a very high melting point and it does not conduct electricity.
Layers of hexagonal rings formed by covalent bonds between the carbon atoms. There are no covalent bonds between the layers which means they are free to slide over each other.
A single layer of graphite.
Electronics and composites.
Molecules of carbon atoms with hollow shapes.
Hexagonal rings of six carbon atoms, but they may also have rings of 5 or carbon atoms.
High length to diameter ratios (long and thin).
Their properties make them useful for nanotechnology, electronics and materials.
As no atoms are lost or made in a chemical reaction, the mass of the products will equal the mass of the reactants.
Hydrogen = 2, Oxygen = 1.
Nitrogen = 1, Hydrogen = 3.
Calcium = 1, Oxygen = 2, Hydrogen = 2.
2H2 + O2 → 2H2O
Cl2 + 2KI → 2KCl + I2
The sum of the relative atomic masses of the atoms in the compound.
H = ( 1 x 2 ) = 2; S = ( 1 x 32 ) = 32; O = ( 16 x 4 )= 64; = 98
Na = ( 23 x 2 )= 46; C = ( 1 x 12 ) = 12; O = (16 x 3 )= 48; =106
Ca = (1 x 40) = 40; O = (16 x 2 ) = 32; H = (1 x 2 )= 2; = 74
In a non-enclosed system one of the reactants or products may be a gas and its mass has not been measured.
When a metal reacts with oxygen the mass of the metal oxide will be more than the mass of the metal because of the addition of oxygen gas.
When a metal carbonate decomposes the mass of the products will appear less than the mass of the reactants because carbon dioxide gas is given off.
Uncertainty is the amount of error in your measurements.
The range is the highest repeat value minus the lowest repeat value.
A large range suggest the measurements are imprecise and there is a large uncertainty about the results.
Uncertainty = range / 2.
Range = 20.1 - 19.8 = 0.3mL;
Uncertainty = 0.3 / 2 = 0.15mL.
Uncertainty of the mean = 20.0 +/- 0.15
The mass of 1 mole of a substance is equal to its relative formula mass in grams. E.g. Mr of carbon = 12; therefore 1 mole of carbon has a mass of 12g.
The number of particles in one mole of carbon is equal to the number of particles in one mole of carbon dioxide.
6.02 x 1023 per mole
Number of moles = mass in grams / Mr of the substance
Number of moles = 44 / (1 x 2) + 16;
Number of moles = 44 / 18;
Number of moles = 2.4 mol
Rearrange the equation; mass = number of moles x Mr of the substance; mass = 0.4 x (12 + (16 x2); mass = 0.4 x 44; mass = 17.6g
1 mole of magnesium reacts with 2 moles of hydrochloric acid to form 1 mole of magnesium chloride and 1 mole of hydrogen.
Percentage mass of an element in a compound = (Ar x number of atoms of the element / Mr of the compound) x 100
Divide the mass of each substance by its relative formula mass to find the number of moles of each substance. Divide the number of moles of each substance by the smallest number of moles in the reaction. If the any of the numbers are not whole numbers, multiply all the numbers so that they become whole numbers.
Number of moles of magnesium = 12 / 24 = 0.5 moles ;
Number of moles of oxygen = 8 / (16 x 2);
Number of moles of oxygen = 8 / 32 = 0.25 moles.
Number of moles of MgO = 20 / 40 = 0.5 moles.
Divide each substance by the smallest number of moles in the reaction (oxygen = 0.25);
Mg = 0.5 / 0.25 = 2; O2 = 0.25 /0.25 = 1; MgO = 0.5 / 0.25 = 2.
The balanced equation for the reaction is: 2Mg + O2 → 2MgO
The limiting reactant limits the amount of product made in a reaction.
To ensure that the other reactants involved are used up.
The mass of the limiting reactant
Write out a balanced equation.
4Al + 3O2 → 2Al2O3.
Calculate the relative formula masses of aluminium (27) and aluminium oxide (102).
Calculate the number of moles from the substance you are given the mass of (aluminium).
Moles of aluminium = mass / Mr: Moles of aluminium = 135 / 27 = 5.
Using the balanced equation calculate the number of moles of the other substance.
4 moles of aluminium react to produce 2 moles of aluminium oxide (half the number of moles).
So 5 moles of aluminium would produce 2.5 moles of aluminium oxide.
Use the number of moles to calculate the mass.
Mass of aluminium oxide = moles x Mr;
Mass of aluminium oxide = 2.5 x 102 = 255g
Write out a balanced equation.
Cl2 + 2KI → 2KCl + I2.
Calculate the relative formula masses of potassium chloride(74.5) and potassium iodide (166).
Calculate the number of moles from the substance you are given the mass of (potassium iodide).
Moles of potassium iodide = mass / Mr: Moles of potassium iodide = 24 / 166 = 0.14 moles.
Using the balanced equation calculate the number of moles of the other substance.
2 moles of potassium iodide react to produce 2 moles of potassium chloride.
So 0.14 moles of potassium iodide would produce 0.14 moles of potassium chloride.
Use the number of moles to calculate the mass.
Mass of potassium chloride = moles x Mr;
Mass of potassium chloride = 0.14 x 74.5 = 10.4g
A solution consists of a solute (solid) dissolved in a solvent (liquid)
The solid part of a solution which has been dissolved.
The liquid part of the solution.
Concentration = mass of the solute (g) / volume of solvent (dm3)
1000cm3 = 1 dm3
Oxidation occurs when a substance gains oxygen.
Reduction occurs when a substance loses oxygen.
Metals form positive ions
The reactivity of a metal is related to the ease by which it can form ions (lose electrons).
Potassium, sodium, lithium, calcium, magnesium, zinc, iron and copper.
Carbon and hydrogen.
Potassium, sodium, lithium, calcium, magnesium, carbon, zinc, iron, hydrogen and copper.
A displacement reaction.
Metal + water → metal hydroxide + hydrogen.
2Na + H2O → Na2O + H2.
Metal + acid → salt + water.
Ca + H2SO4 → CaSO4 + H2O.
Metals are usually found as compounds in the Earth.
A metal compound which is mined.
Because it is unreactive and does not form compounds.
These metals are extracted from their oxides by reduction with carbon. This works because these metals are less reactive than carbon.
Iron oxide (Fe2O3) is reduced (loses oxygen). Carbon (C) is oxidised (gains oxygen).
Oxidation is electron loss.
Reduction is electron gain
Fe(s) + Cu2+(aq) →Cu(s) + Fe2+(aq).
An ion that takes no part in the reaction.
Fe → Fe2+ + 2e-
2H+ + 2e- → H2.
Salt and hydrogen.
Oxidised: magnesium, Reduced: hydrogen.
Oxidised: zinc, Reduced: hydrogen.
Oxidised: iron, Reduced: hydrogen.
Soluble metal hydroxides.
Insoluble metal hydroxides and metal oxides.
By reacting with alkalis or bases.
Metal oxide + acid → salt + water.
Metal hydroxide + acid → salt + water.
Metal carbonates + acid → salt + water + carbon dioxide (bubbles!)
The acid used and the positive (metallic) ions in the alkali or base.
React an acid with an insoluble substance (e.g. metal, metal oxide, metal hydroxide or metal carbonate).
Add the solid till no more reacts. The unreacted powder will be visible in the beaker.
Excess acid is filtered off and the solution of the new salt is collected.
The acidity or alkalinity of a solution.
1 - 6.
8 - 14.
Using a wide range indicator (e.g. universal indicator) or a pH probe.
H+ + OH- → H2O.
A strong acid is completely ionised in solution.
Hydrochloric, nitric and sulfuric acids.
A weak acid is only partially ionised in solution.
Ethanol, citric and carbonic acids.
Dilute and concentrated refer to the amount of substance in a solution (e.g. the number of moles). Weak and strong refer to the amount of ionisation that has occurred.
The stronger the acid, the lower the pH.
As pH concentration decreases by one unit (e.g. from 5 to 4), the hydrogen ion concentration increases by by a factor of ten (e.g. from 10 to 100).
Molten (liquid) or in an aqueous solution.
Liquids or solutions that are able to conduct electricity
Positive charged ions move to the negative electrode (cathode). Negatively charged ions move towards the positive electrode (anode). The ions are gain or lose electrons at the electrodes producing elements.
Pb2+ and Br-.
The metal ions are attracted to the negative electrode (cathode). The non-metal ions are attracted to the positive electrode (anode)
2Br- → Br2 + 2e-.
Pb2+ + 2e- → Pb
Zn2+ and Cl-.
Chlorine will be formed at the positive electrode (anode) and zinc will be formed at the negative electrode (cathode).
Metals can be extracted from molten compounds.
Metals which are too reactive to be extracted by reduction with carbon. Metals which react with carbon.
Large amounts of energy are used in the extraction process to melt the compounds and to produce the electrical current for electrolysis.
Aluminium is extracted by the electrolysis of a mixture of aluminium oxide and cryolite using carbon as the positive electrode (anode)
Al3+ + 3e- → Al.
2O2- → O2 + 4e-.
To reduce the melting point of aluminium oxide.
The oxygen formed at the positive electrode (anode) reacts with the carbon in the electrode.
H+ and OH-.
The relative reactivity of the elements involved.
If the metal ion is less reactive than hydrogen the metal will be formed. Otherwise, hydrogen will be released.
Oxygen is produced unless the solution contains halide ions in which event a halogen will be produced.
H+, OH-, Cu2+ and SO42-
Copper is less reactive than hydrogen so copper is formed at the negative electrode (cathode). As copper sulfate contains no halide ions oxygen will be formed at the positive electrode (anode).
H+, OH-, Na+ and Cl-
Sodium is more reactive than hydrogen so copper is formed at the negative electrode (cathode). As there are halide ions present in solution (the chloride ions) chlorine gas will be given off at the positive electrode (anode).
Positive metal ions or hydrogen gain electrons.
Negative non-metal ions lose electrons
At the negative electrode (cathode): Cu2+ + 2e- → Cu. At the positive electrode (anode): 4OH- → O2 + 2H2O + 4e-.
At the negative electrode (cathode): 2H+ + 2e- → H2. At the positive electrode (anode): 2Cl- → Cl2 + 2e-.
Energy is conserved in chemical reactions.
The product molecules have less energy than the reactant molecules.
The reactant molecules have less energy than the reactant molecules.
A reaction that transfers energy to the surroundings, increasing the temperature of the surroundings.
Combustion, oxidation reactions and neutralisation reactions.
A reaction that transfers energy from the surroundings, decreasing the temperature of the surroundings.
Thermal decomposition, the reaction between citric acid and sodium hydrogencarbonate and some sports injury packs.
Place 25mL of 0.25mol hydrochloric acid and 25mL of 0.25mol sodium hydroxide into separate beakers.
Measure the temperature of both reagents and ensure they are equal.
Place a polystyrene beaker in a large beaker and surround with cotton wool balls for insulation.
Now add both chemicals to the polystyrene cup and cover with a lid with a thermometer through the middle.
Measure the temperature of the mixture every 30 seconds and record the highest temperature reached.
Repeat the experiment with 0.5mol and 1.0mol solutions.
Plot the highest temperatures against concentration.
A chemical reaction occurs when particles collide with each with sufficient energy.
The minimum amount of energy the particles must have for a reaction to take place.
A graph to show the change in energy between reactants and products over the course of a reaction.
Energy needs to be supplied to break bonds in the reactants. Energy is released when bonds in the products are formed.
The energy needed to break or form bonds between atoms.
Calculate the difference between the sum of the energy needed to break the bonds of the reactants and the sum of the energy released when bonds of the products are formed.
The energy released from forming new bonds is greater than the energy needed to break existing bonds (e.g. the products have less energy than the reactants).
The energy needed to break existing bonds is greater than the energy needed to break existing bonds (e.g. the products have more energy than the reactants).
Energy in = 436 (H-H) + 243 (Cl-Cl ) = 679kJ/mol.
Energy out = (2 x 432)(2 x H -Cl) = 864kJ/mol;
Energy change = energy in - energy out = 679 - 864 = -185kJ/mol; the energy change is negative so the reaction is exothermic.
Energy in = (2 x 366)(2 x H-Br) = 732 kJ/mol;
Energy out = 436 (H-H) + 193 (Br-Br) = 629kJ/mol;
Energy change = energy in - energy out = 732 - 629 = + 103kJ/mol; the energy change is positive so the reaction is endothermic.
By measuring the the quantity of the reactant as it is used or the quantity of the product as it is formed.
Mean rate of reaction = quantity of reactant used / time taken.
Mean rate of reaction = quantity of product formed / time taken.
Mass in grams, volume in cm3 or moles.
g/s, cm3/s or mol/s
A straight line that touches the curve but does not cross it.
The rate of reaction at a particular point.
Concentration of reactants, pressure of reacting gases, surface area of reactants, temperature of the reaction and the presence of catalysts.
Increasing concentration of reactants increases the number of colliding molecules.
Increasing pressure of reacting gases increases the number of collisions between molecules
Large surface area of reactants increases number of colliding molecules.
Increasing temperature of the reaction increases number of collisions.
The presence of catalysts lowers the activation energy.
A measure of how cloudy a solution is.
Add a set volume and concentration of sodium thiosulfate to a conical flask. Place the flask on a black cross drawn on paper. Add a known volume of hydrochloric acid to the conical flask. Start the stopwatch. Time how long it takes for the cross to disappear (due to turbidity of the reacting solution). Repeat the reaction for different concentrations of hydrochloric acid.
Add a set volume and concentration of hydrochloric acid to a conical flask. Add a set mass of magnesium to the flask. Place a bung with a tube attached to a gas syringe on top of the flask. Start the timer. Note the volume of gas produced every 20 seconds until the reaction stops. Repeat the experiment using different concentrations of hydrochloric acid.
Chemical reactions occur when reacting particles collide with each other and with sufficient energy.
The minimum energy particles must have to react.
Increasing the concentration means there are more particles and as a result there are more collisions. This will increase the rate of reaction.
Increasing the pressure means there are more particles near each other so they are more likely to collide. This increases the rate of reaction.
Increasing the surface area (by breaking into smaller pieces) increases the number of particles available to collide. This increases the rate of reaction.
Breaking up a solid into smaller pieces increases the surface area to volume ratio which will speed up the rate of reaction.
Increasing the temperature increases the speed of the particles. As they are moving faster they will collide more frequently and with more energy.
A substance that changes the rate of a chemical reaction but is not used up in the process.
Catalysts work by providing a pathway for the reaction which has a lower activation energy.
Enzymes are biological catalysts found in living organisms.
A reaction profile is a graph which shows the levels of energy required over the course of a reaction.
A reaction where the products of the reaction can react to produce the original reactants.
A + B ⇌ C + D.
By changing the conditions of the reaction.
Ammonium chloride ⇌ ammonia + hydrogen chloride.
If heated the reaction will move to the right (produce ammonia and hydrogen chloride). If cooled the reaction will move to the left (produce ammonium chloride).
The compound is associated with water molecules.
The compound has no water molecules associated with it.
Hydrated copper sulfate ⇌ anhydrous copper sulfate + water. The reaction is endothermic to the right (formation of anhydrous copper sulfate) and exothermic to the right (formation of hydrated copper sulfate).
Equilibrium occurs when the forward and reverse reactions occur at exactly the same rate (no apparent change).
Apparatus which prevents the escape of the products or reactants of a reaction.
They depend on the conditions of the reaction.
The system will respond to counteract the change.
If the conditions of a reaction in equilibrium are changed the system will respond to counteract the change. This results in a new point of equilibrium.
To the right (ammonia and hydrogen chloride formed).
To the left (ammonium chloride formed).
To the right (anhydrous copper sulfate and water formed).
The system will no longer be in equilibrium. The concentrations of the substance will change until equilibrium is reached again.
More products will be formed until equilibrium is reached.
More reactants will react until equilibrium is reached.
More is NH3 produced.
More is NH3 produced.
More N2 and H2 will react.
The relative amount of products at equilibrium decrease.
The relative amount of products at equilibrium increase.
The relative amount of products at equilibrium increase.
The relative amount of products at equilibrium decrease.
The relative amounts of NH3 will increase at equilibrium.
The relative amounts of NH3 will decrease at equilibrium.
A decrease in pressure will cause the reaction to shift to the side with the larger number of molecules (from the balanced symbol equation).
An increase in pressure will cause the reaction to shift to the side with the smaller number of molecules (from the balanced symbol equation).
The are less molecules on the left (2 moles compared to 4 moles) so the reaction will shift to the right (more NH3).
The are more molecules on the right (4 moles compared to 2 moles) so the reaction will shift to the left (more N2 and H2).
Crude oil is the remains of biomass consisting mainly of plankton buried in mud.
Crude oil is a mixture of a very large number of compounds, mainly hydrocarbons.
Hydrocarbons are molecules made up of carbon and hydrogen only.
Methane (C1), ethane (C2), propane (C3) and butane(C4).
Groups of molecules with a similar number of carbon atoms.
The petrochemical industry processes fractions for fuels and feedstock.
Petrol, diesel oil, kerosene, heavy fuel oil and liquified petroleum gas.
Solvents, lubricants, polymers and detergents.
Carbon atoms have the ability to form families of similar compounds.
Crude oil is heated until most of it turns to gas.
The gases enter the base of the fractionating column.
The fractionating column has a temperature gradient. It is hot at the bottom and cool at the top.
The longer hydrocarbons have high boiling points so they condense at the bottom of the column (e.g. bitumen, heavy fuel oil and diesel oil). Shorter hydrocarbons have low boiling points so they condense at the top of the column (e.g. kerosene, petrol and liquified petroleum gas).
Boiling point, viscosity and flammability.
A measure of how a substance flows (high viscosity = low flow).
As chain length increases, boiling point increases, viscosity increases and flammability decreases.
Carbon and hydrogen.
Hydrocarbon + oxygen → carbon dioxide + water.
CH4 + 2O2 → CO2 + 2H2O
C3H8 + 5O2 → 3CO2 + 4H2O
The breakdown of hydrocarbons into smaller, more useful molecules.
Catalytic cracking and steam cracking.
Catalytic cracking is when long chain hydrocarbons are heated and vapourised.
The gas is passed over a catalyst (e.g. aluminium oxide powder) where the long chains are broken down into smaller chains.
Steam cracking is when long chain hydrocarbons are heated, vapourised and mixed with steam.
The mixture is heated to a high temperature and the long chains are broken down into short chains.
Alkanes and alkenes.
Alkenes are more reactive than alkanes.
Orange bromine water is added to the hydrocarbon. The mixture is shaken.
If the hydrocarbon is an alkenes the orange bromine water will become colourless.
If the hydrocarbon is an alkene, the bromine water will stay orange.
Because there is a high demand for fuels with small molecules.
They are used to produce polymers and are the starting materials for many chemicals.
C6H14 → C4H10 + C2H4.
A single element or compound that is not mixed with any other substance
Pure substances have specific melting and boiling points.
A mixture which has been designed as a useful product.
Formulations are made by mixing specific chemicals in measured quantities.
Fuels, cleaning agents, paints, medicine, alloys, fertilisers and foods.
Chromatography is a method of separating mixtures and identifying substances.
The solvent in which the stationary phase is placed.
Usually a solid on which the samples are placed.
Separation by chromatography depends on the distribution of substances between the mobile and stationary phases.
The line at the bottom of the paper where the samples are placed.
The line to denote the distance travelled by the mobile phase.
Rf = distance moved by substance / distance moved by solvent
A pure compound will only produce a single spot on a chromatograms. A mixture will separate into two or more spots.
Rf=90/120: Rf = 0.75 (no units)
Place different coloured sweets in a Petri dish.
Add drops of water to each sweet to wash of the colour.
Draw a line using a pencil about 2cm from the bottom of the paper.
Carefully spot each dye onto the line.
Place the paper into a beaker containing about 1cm depth of solvent.
Leave the solvent to move up the paper for 20 mins or until it reaches near the top of the paper.
Remove the paper and mark the level the solvent reached within a pencil line.
Identify the number of spots for each sample.
Calculate the Rf value for each of the spots.
Pure samples will only have one spot.
Place a burning splint at the mouth of a test tube containing a gas. If hydrogen is present, a popping sound will be heard.
Place a glowing splint at the mouth of a test tube containing a gas. If oxygen is present the splint will relight.
Bubble a gas through an aqueous solution of calcium hydroxide (lime water). If carbon dioxide is present the lime water will turn cloudy.
A piece of damp litmus paper is placed at the mouth of a test tube containing a gas. If the gas is chlorine the litmus paper will be bleached and turn white.
200 million years
Four-fifths (about 80%)
One-fifth (about 20%)
Carbon dioxide, water vapour and noble gases.
4.6 billion years
Consisted mainly of carbon dioxide with little or no oxygen. It may have been similar to the atmospheres of Mars or Venus today.
Intense volcanic activity released gases and water vapour that formed the early atmosphere. The water vapour condensed to form the oceans.
Methane and ammonia.
After the oceans were formed carbon dioxide dissolved in the water to form carbonates.
These carbonates precipitated out of the water and were laid down as sediments (e.g. chalk).
This reduced the levels of carbon dioxide in the atmosphere.
About 2.7 billion years ago
Algae and plants.
carbon dioxide + water → glucose + oxygen
6CO2 + 6H2O → C6H12O6 + 6O2
Plants evolved and the production of oxygen increased. This increase in oxygen enabled animals to evolve.
Respiration, converted to starch for storage, converted to fat or oil for storage, converted to cellulose to make the cell wall, used to make amino acids for protein synthesis.
Greenhouse gases maintain temperatures on Earth at a high enough level to support life.
Water vapour, carbon dioxide and methane.
The sun emits short wave radiation which is not absorbed by greenhouse gases.
The short wave radiation is absorbed by the Earth, warming it.
This heat is emitted from the Earth as long wave radiation.
Greenhouse gases absorb long wave radiation.
The more greenhouse gases there are the more long wave radiation is absorbed causing a rise in temperature.
Carbon dioxide and methane.
Deforestation and burning fossil fuels.
Agriculture (cattle ranches, rice) and landfill sites.
An increase in the temperature of the Earth’s atmosphere which will result in global climate change.
The data published has been subjected to peer review (checked by other scientists) to ensure the data is not inaccurate or biased.
It is difficult to model a complex system such as the environment. In an effort to help people understand the issue, simplified models are often used. This can lead speculation and opinions presented by the media which is based only on parts of the evidence and may be biased or lack all the evidence.
An increase in average global temperature.
Polar ice caps melting, changes in rainfall, changes in temperature, frequency and severity of storms, availability of water.
Melting of ice caps could lead to a rise in sea levels, flooding and coastal erosion.
Changes in rainfall patterns could cause a change in the distribution of water and affect the ability to produce food.
Severe storms will damage infrastructure and cause more people to become homeless and increase the spread of diseases such as cholera.
The rise in temperature and availability of water may affect habitats and affect the distribution of wild species.
The total amount of carbon dioxide and other greenhouse gases emitted of the life cycle of a product service or event.
Reduce the emissions of carbon dioxide and methane.
Use renewable energy or nuclear power.
Use efficient processes to conserve energy and cut waste.
Introduce a carbon tax to reward companies who reduce their carbon footprint.
Put a cap on greenhouse emissions.
Capture carbon dioxide from the atmosphere.
Countries do not want to sacrifice economic development. Individuals need to change habits and need to be educated how to do so.
Carbon, hydrogen and sulfur.
Carbon dioxide, water vapour, carbon monoxide, sulfur dioxide and oxides of nitrogen.
Solid particles and unturned hydrocarbons.
A small aggregation of carbon.
Incomplete combustion occurs.
Solid particles of soot (carbon), carbon monoxide and carbon dioxide.
Small amounts of sulfur is found in coal. This reacts with oxygen to form sulfur dioxide.
Oxides of nitrogen at formed at high temperatures found in internal combustion engines.
A toxic colourless and odourless gas.
Combines easily with haemoglobin in your blood and prevents oxygen from being taken up by the red blood cells.
Health problems such as aggravating asthma.
To provide warmth, shelter, food and transport.
Food, timber, clothing and fuels.
Energy and materials.
Development that’s meets the needs of the current generations without compromising the ability of future generations to meet their own needs.
Rubber (a natural product) has been replaced by man made polymers. Cotton (a natural product) has been replaced by synthetic fibres such as polyester or Lycra. Plant dyes (a natural product) have been replaced by synthetic dyes.
Resources which are not formed quickly enough to be replaceable.
Fossil fuels, nuclear fuels and metal ores.
A resources that forms at a faster or similar rate than they are being used.
Timber, fresh water and food.
Water that is safe to drink.
It should have only low levels of dissolved salts and microbes.
Potable water contains dissolved substances so it is not pure.
Rain is the source of most water in the UK. It collects in the ground and in lakes and rivers.
Water from a suitable source (e.g. reservoir or ground water) is passed through filter beds and then sterilised.
Chlorine, ozone or ultraviolet light.
Salt water or sea water.
Distillation or reverse osmosis.
These processes require large amounts of energy.
Take a sample of water and measure its pH.
Filter the water using filter paper and a funnel to remove undissolved solid particles.
Measure the mass of a round bottom flask.
Place the water into a round bottom flask and attach to simple distillery.
Collect the water that evaporates and condenses from the equipment.
Retest the water for pH.
Collect the round bottom flask and weigh it.
Calculate the mass of dissolved solids remaining.
Repeat the experiment with different samples of water.
Urban lifestyles, industrial processes and agriculture.
These require treatment to remove organic matter and harmful microbes.
These require treatment for the removal of organic matter and harmful chemicals.
Screening and grit removal; sedimentation to produce sludge and effluent; anaerobic digestion of sludge; aerobic biological treatment of effluent.
Waste water requires expensive treatment to remove potentially toxic chemicals and microbes from the water. Ground water water just needs to be filtered and sterilised before it is potable. Saltwater can be purified but the processes require a lot of energy.
Copper ores are becoming scarce.
Phytomining and bioleaching.
They do not involve digging, moving and disposing of large amounts of rocks.
Phytomining uses plants to absorb metal compounds. The plants are harvested and then burned to form ash that contain metal compounds.
Bioleaching uses bacteria to produce leachate solutions that contain metal compounds.
A liquid removed from the ground containing dissolved substances from the ground.
By displacement reactions with scrap iron or by electrolysis.
These are assessments of the environmental impact of a product at each stage of its life.
Extracting and processing raw materials;
Manufacturing and packaging of product;
Use and operation of product;
Disposal of product.
Most have no effect, some influence the phenotype and a small proportion determine the phenotype.
Selective or abbreviated LCAs can be misused to reach pre-determined conclusions (e.g. for advertising campaigns).
Reduction in use, reuse and recycling.
Reduce use of limited resources, reduce use of energy sources, reduction in waste and environmental impacts.
Metals, glass, building materials, clay ceramics and plastics.
Quarrying and mining.
Glass bottles can be crushed and melted to make different glass products.
They are recycled for a different use.
By melting, recasting or reforming into different products.
Depends on the material and the properties required of the final product.
Scrap steel can be added to iron from a blast furnace to reduce the amount of iron that needs to be extracted from iron ore.