Fadi Munir

Chemistry Study Guide

What are the kinds of matter around us and what are they called?Solids, liquids and gases. And they are called the three states of matter.

What are the properties of solids, liquids and gases?Solid Liquid Gas

Does not change shape. Take the shape of the container that holds them. Have no shape.

Particles are closely packed together with no gaps and can only vibrate but not move position.

Particles are also closely packed together with no gaps but can move position and vibrate.

Particles are very far apart and do not touch. They move fast and randomly and vibrate.

Slightly expand when heated and melt into a liquid.

Slightly expand when heated and boil into a gas. Expand a lot when heated.

Slightly contract when cooled. Slightly contract when cooled and freeze into a solid.

Contracts a lot and can condense into a liquid.

Difficult to compress. Easily compressible.

Density of most solids is around 0.5-20g/cm3

Density of most liquids at room temperature is about 1g/cm3

Density of most gases at room temperature is a tiny fraction, about 0.001g/cm3

Vibrational motion. Translational and rotational motion.

What is sublimation?Sublimation is a process in which a solid is converted into a gas directly without any traces of liquid.

Can you give examples of sublime substances? Solid carbon dioxide (dry ice) Iodine Snow and ice (water) Camphor

How do particles move?All particles have kinetic energy that causes them to move. When particles are heated they must move because of their energy. Even solids. When a solid is heated the particles vibrate faster, to vibrate faster the solid needs more space, so the particles move slightly further apart. This is why solids slightly expand when heated.

Explain all the processes of the states of matter.If you heat a solid enough, the particles vibrate faster and faster, moving further and further apart, until they eventually move out of their fixed positions, this means the solid has become a liquid. Now, if you go through the same process with a liquid, the particles vibrate and move apart until they are not touching each other anymore and can move around freely and randomly, thus the liquid has become a gas.

What do you know about Potassium manganate/permanganate?It is a solid that dissolves in water to give a deep purple solution.

What is diffusion?Diffusion is when potassium manganate crystals dissolve in water and gradually the purple colour spreads through the liquid.

Page | 1

Fadi Munir

Explain the diffusion of bromine and potassium manganate.Liquid bromine moves faster in gas than potassium manganate crystals in liquid.

What would happen if you put a filter paper between two jars of diffused bromine?The filter paper does not stop bromine particles from diffusion because the particles are much smaller than the holes in the filter paper.

What does the gas diffusion rate depend on?The diffusion rate of a gas depends on how heavy its particles are: small, light (not heavy) particles like hydrogen move much faster than larger, heavier particles like carbon dioxide.

What is Brownian movement?It was thought that tiny particles were moving because they were alive, but botanist, Robert Brown showed that charcoal dust also moves in the same way. This was explained years later by Albert Einstein with the Kinetic Particle Theory.

What makes smoke particles move?Smoke particles are small pieces of carbon floating in the air, they are made up of millions of tiny carbon particles, and the smoke particles move because they are being knocked around by the air particles around them.

Why can the smell of cooking spread into the street (or perfume)?Because smells are caused by gas particles mixing with air and moving through it, they dissolve in the moisture of the lining of your nose.

What are atoms?Atoms are the very smallest particles of matter that we cannot chemically breakdown further by chemical means.

What are molecules?Molecules are two or more atoms chemically combined together.

What are ions?Ions consist of atoms or are a group of atoms that carry a charge, such as potassium manganate.

What is lattice?Lattice is the pattern of arrangement in particles.

What is gas pressure, and what does it depend on?Gas pressure is when gas particles collide with each other and hit the sides of the container, meaning the gas exerts pressure on it. This pressure depends on temperature of the gas and the volume of the container.

What is relative molecular mass?The particles of gases are molecules, the mass of molecules is called relative molecular mass. The lower the relative molecular mass, the faster a gas will diffuse.

What is a mixture?A mixture is a liquid that contains more than one substance, they are just mixed together, not chemically combined. For example, air is a mixture of nitrogen, oxygen and other gases.

Page | 2

Fadi Munir

What is a solution?When substances are dissolved in water, the mixture is called a solution, for example, sugar as a solute and water as a solvent. So solute + solvent = solution.

How do you get the solute?By filtering.

What is aqueous solution?A solution in water.

What are volatile solvents?Volatile solvents are solvents that easily evaporate at room temperature, such as white spirit, propanone (acetone) and ethanol.

Why do glues and paints dry easily?Because they are volatile.

Why does aftershave feel cool?Because it is volatile and cools the skin when evaporated.

Why do volatile liquids easily evaporate?Because forces between its particles are weak. Also, they have low boiling points.

What are pure substances?Substances that are made up only with one kind of atom and have no other substances mixed with it.

Does impurity matter?Often it does not matter, but sometimes purity is very important, when you are making medical drugs or flavouring for food, you must make sure it contains nothing that is harmful.

What are impurities?Unwanted substances that are mixed with substances you want.

How do you check if a substance contains any impurities?Its melting point falls and its boiling point rises. It melts and boils over a range of temperatures. The more impurities there are, the bigger the change in melting/boiling point.

What are methods of separation?To separate: You should use:A solid from a liquid FiltrationA solute from its solution Crystallisation/EvaporationA solvent from a solution Simple distillationLiquids from each other Fractional distillationDifferent substances from a solution Paper chromatography

In filtering, what is residue and filtrate?For example, chalk is insoluble in water. So it is easy to separate by filtering. The chalk is trapped in the filter paper, while the water passes through. The trapped solid is called the residue. The water is the filtrate.

Page | 3

Fadi Munir

Explain crystallisation.Crystallisation is obtaining many solids from their solutions by letting crystals form. This process is called crystallisation. It works because soluble solids tend to be less soluble at lower temperatures. For example, copper sulphate solution in water when heated, evaporates the water; so the solution becomes more concentrated. So, the solution becomes saturated. If you cool the solution, crystals form. Then the crystals can be separated by filtering.

Explain evaporation.Some substances have little solubility changes when the temperature falls, therefore crystallisation doesn’t work with these substances. Salt in an aqueous solution is an example. Heat the solution to evaporate the water, until there is little water left, salt will start to appear. Heat carefully until it is dry.

Explain separating two solids.To separate two solids, choose a solvent that would dissolve one and not the other. For example, water dissolves salt but not sand. Add water to the mixture and stir. The salt dissolves. Filter the mixture and the sand will trap in the filter paper. Rinse sand with water and dry it in the oven. Evaporate the water from the salt solution to get the dry salt.

How do you separate two solids that have dissolved in water? For example, a mixture of sugar and salt.We use ethanol as a solvent which dissolves sugar but not salt. The sugar will dissolve in the ethanol. When we filter the mixture, the salt will be trapped in the filter paper as residue and the sugar solution will pass through as the filtrate. To get sugar we will evaporate the solution over a water bath since ethanol is flammable.

How do you separate a mixture of sand and little bits of iron wire?Using a magnet to trap the iron wires, so you have the iron and you have the sand.

Explain simple distillation.Simple distillation is a way to obtain a solvent from a solution. For example, salt solution. Heat the salt solution until it boils. Water vapour rises into the condenser leaving the salt behind. The condenser is cold, so the water vapour condenses to water. This is called distilled water.

Explain fractional distillation.It is used to separate a mixture of two liquids from each other by making use of the liquids’ different boiling points, for example: separation of a mixture of ethanol in water. Heat the mixture at the lower boiling point (78o C for ethanol). The ethanol will begin to boil. Some water will also evaporate with the ethanol. So the mixture of ethanol and water vapour will rise in the fractionating column with glass beads. The two vapours condense in the glass beads making them hot. When the beads reach 78o C, the ethanol vapour continues evaporating and proceeds into the condenser, to condense back to pure ethanol. While the water vapour condenses back to drops in the flask

Explain fractional distillation in industry.It is important in petroleum industry to refine crude oil in to petrol and other compounds. The oil is heated and the vapours rise to different heights up to tall, steel fractionating columns.

Page | 4

Fadi Munir

Explain paper chromatography.This method can be used to separate a mixture of substances. For example, it can be used to find how many different dyes there are in black ink.

How do you separate a drop of black ink by paper chromatography?Place a drop of black ink on the centre of a filter paper, let it dry and add three or four more drops on the same, original spot. Now, drop water on the spot, one drop at a time. The ink slowly separates into rings of different colours.

Why does the black ink separate into different colours?The dyes in the ink drop have different solubilities in water, so they travel across the paper at different rates, the most soluble travels fastest. The filter paper with these coloured rings is called chromatogram (‘Chroma’ means colour).

How is paper chromatography useful? For identifying substances, And separating mixtures of substances, And purifying substances by separating them from their impurities.

What does paper chromatography depend on?Paper chromatography depends on how the substances in a mixture interact with the solvent and chromatography paper.

What’s the key idea of chromatography?The key ideas of chromatography is that it is detective work and you need to have two phases, a stationary phase such as filter paper; and a mobile phase which includes the solvents you use.

Why do substances in the mixture separate?Because each substance has different levels of attraction to the solvent and stationary phase (filter paper).

What is the stationary phase? It could be paper in paper chromatography, A thin coat of an absorbent on a glass plate or inside a tube, Plastic beads packed into a tube.

What is the mobile phase? In paper chromatography, it is the solvent, A mixture of inert (unreactive) gases, this is gas chromatography.

What are the uses of chromatography?Chromatography can be used on a small scale in the lab, or in a large scale in industry. In a small scale it is used to identify substances, check purity, help in crime detection and identify air or water pollutants. In a large scale it is used to separate pure substances, (for example making medical drugs or food flavouring) and separating individual compounds from groups of compounds.

What are atoms?Atoms are the smallest particles of matter; that we cannot break down further by chemical means.

What do atoms consist of?

Page | 5

Fadi Munir

Each atom consists of a nucleus and a cloud of electrons that whizz around the nucleus.

What is an element and how many are there?An element is a substance that contains only one kind of atom. Around 90 elements have been found in the Earth. Around 30 have been made in labs, most of these are very unstable so they are not found in the Earth.

What do you find in the nucleus of an atom and how do you measure its mass?The nucleus is made of protons, electrons and neutrons. Since all the particles in an atom are very light, we measure their mass in atomic mass units, rather than grams.

Which particles in an atom have a charge and give their mass?Particles in an atom Mass Electric chargeProtons 1 amu Positive charge (+1)Neutrons 1 amu No charge/Neutral (0)Electrons 1/1840 amu Negative charge (-1)

Which particles are the heaviest in the nucleus, and where are they found?Protons and neutrons are the heaviest and cluster together in the centre of the nucleus.

Where are the electrons found in a nucleus?Electrons circle very fast around the nucleus at different energy levels. These energy levels are called shells.

How can you identify an atom, give reasons?You can identify an atom by the number of protons it contains, this is because the atoms of elements have unique numbers of protons, and every other atom has different numbers of protons.

What is the number of protons in atom called?Proton number/ Atomic number.

Do atoms have a charge?Every atom has an equal number of protons and electrons. So atoms have no overall charge, since the positive and negative charges cancel each other out.

What is the nucleon number?The total number of protons and neutrons in an atom is called its nucleon number. This is also called the mass number.

How do you know the particles in an atom using the periodic table?The lower number is always the proton number. The top number is the nucleon/mass number. To find the neutrons, you subtract the two numbers.

Since protons, neutrons and electrons make up an atom, what are they called?Sub-atomic particles.

What are isotopes, is there a lot?Isotopes are atoms of the same element, with different numbers of neutrons. Most elements have isotopes.

Page | 6

Fadi Munir

What is radioactivity?Some atoms are radioactive. This means that their nucleus is unstable. The atom eventually breaks down (decays), giving out radiation in the form of rays and particles, and a lot of energy.

What are radioisotopes?Radioactive isotopes

What can radiation contain?Radiation may contain alpha particles, beta particles, gamma rays and neutrons.

Alpha particles are made up of 2 protons and 2 electrons. Beta particles are electrons that move at high speed. Gamma rays are rays with high energy. Neutrons

What can radiation cause to humans?If radiation gets into your body, it will kill body cells. Large doses cause radiation sickness. Victims vomit, feel tired, lose hair and could eventually die. Even small doses will cause cancer over a long period.

How do we check for radioisotopes?Since radiation is harmful to humans, we check for radiation using a Geiger counter. It gives a reading and you may hear beeps.

How can we make use of radioisotopes?Radioisotopes are dangerous but they are also useful, for example:

We use them to check for gas and oil leaks by adding the radioisotopes to the oil and gas in the pipes. Then, if a Geiger counter detects radiation, there has been a leak. Radioisotopes used in this way are called tracers.

Since radioisotopes cause cancer, we can use them in radiotherapy to cure cancer. The Gamma rays in radiation can kill cancer cells easier than body cells. A beam of gamma rays is aimed carefully at the place of the cancer in the body.

Gamma rays also kill germs. So, gamma rays are used to sterilise syringes and other medical equipment. Gamma rays also kill bacteria that cause food to decay. So, vegetables, fruits and other foods are treated with a low dose of radiation.

Radioisotopes are used as fuel in nuclear power stations because they give out so much energy when they break down.

Name the radioisotope used in radiotherapy and the radioisotopes used in bacteria killing.Cobalt-60 is usually the radioisotope used in radiotherapy. When killing bacteria that cause food to decay, we use cobalt-60 and caesium-137.

How many electrons can each shell hold?The first shell can hold 2 electrons, the second shell can hold 8 electrons, and the third shell can hold 8 electrons.

What are valency electrons?Outer-shell electrons are called the valency electrons. The valency electrons tell you how an element reacts. For example, Group I elements all have similar reactions.

Describe the elements of Group 0.

Page | 7

Fadi Munir

The elements of Group 0 are stable and unreactive because of their stable electron structure.

What are the GENERAL properties of metals and non-metals?Metals: Non-metals:Shiny when polished Not shiny, dullStrong, hard Not strong, not hard, brittleMalleable (Can be hammered)Ductile (Can be made into a wire) Non-malleable, non-ductile, brittle

High melting and boiling points Low melting and boiling points

Good conductors of heat and electricity Poor conductors of heat and electricity (except carbon in the form of graphite)

Sonorous (make ringing noise when struck) Will break up if you strike themHigh density Low densityAlways form positive ions Often form negative ions (Except for hydrogen)When reacting with oxygen, their oxides are alkaline.

When reacting with oxygen, their oxides are acidic.

What are some common uses of metals? Iron is the most used metal in the world. It can be used in buildings, bridges, cars and nail, Copper is used for electrical wiring, Aluminium, is strong but light, so can be used in planes and rockets.

What is sand?Sand is mainly the compound silicon dioxide, formed from silicon and oxygen.

What is a compound?A compound is made of different types of atoms chemically bonded together.

What is a mixture?A mixture contains different substances that are not bonded together.

What are the signs of a chemical change?1. A new substance is formed (precipitate)2. Energy is taken in or given out during the reaction. For example, heat.3. The change is very difficult to reverse.

What are the signs of a physical change?1. No new substance is formed2. Change is very easy to reverse.

What are the noble gases?The elements in Group 0, and they are unreactive.

Why do atoms form bonds?The noble gases are already stable and have full outer shells. This is different with other atoms. Atoms bond with each other in order to gain a stable outer-shell electron structure.

What are ions?When an atom loses or gains electrons, it becomes an ion.An ion is a particle that carries a charge because it has a different number of protons and electrons.How are ions named?

Page | 8

Fadi Munir

Hydrogen and the metals lose electrons, so they form positive ions. The ions have the same names as the atoms. But non-metals form negative ions, so their names end with –ide.

How are ionic compounds named?By putting the names of the ions together with the positive one first.

Give examples of ionic compounds.Magnesium oxide, sodium chloride, magnesium chloride.

Give examples of compound ions.Sodium carbonate, calcium nitrate.

What is a covalent bond?When non-metals both need to gain electrons to gain stable outer-shells, they share electrons by covalent bonding.

What are diatomic elements, give examples?Elements made up of molecules containing two atoms. Such as hydrogen, oxygen, chlorine and nitrogen.

What are the different kinds of covalent bonds?Single, double and triple. When one pair of electrons is shared, the bond is called a single covalent bond. When two pairs of electrons are shared, the bond is called a double covalent bond. When three pairs of electrons are shared, the bond is called a triple covalent bond. A single bond is written as H-H. A double covalent bond is written as O=O. A triple covalent bond is written as NN.

What is a covalent compound, give examples?When atoms of different elements share electrons. Such as hydrochloric acid, water and carbon dioxide.

What is the shape of covalent compounds?Repulsion between the pairs of electrons dictates the shape of the molecule.

What are the properties of ionic compounds? High melting and boiling points because bonds are very strong, Usually soluble in water, Conduct electricity but only when melted or when dissolved in water, and decompose at the

same time.

What are the properties of covalent compounds? Low melting and boiling points because bonds are weak, Usually insoluble in water, Do not conduct electricity because do not carry any charge.

Are all covalent compounds, molecular? Give examples.Some covalent compounds are molecular, so their particles have weak forces of attraction, so have low melting points. But other compounds like diamond (carbon) and silica (silicon dioxide) are different. Diamond and silica have high melting points and have strong forces of attraction, so they are not made of molecules, but they are made of giant covalent structures or macromolecules.

What are allotropes? Give examples.

Page | 9

Fadi Munir

Allotropes are different forms of the same element. Diamond and graphite are allotropes of carbon.

What are metallic bonds?A metallic bond is the attraction between metal ions and free electrons.

What trend is shown in the periods?Change from metal to non-metal.

What are the alkali metals?They are in Group I in the Periodic Table. They are lithium, sodium, potassium, rubidium, caesium and francium.

What are the properties of alkali metals? Silver colour Good conductors of heat and electricity Soft and can be cut with a knife Low melting and boiling points compared against most metals Low density, so float on water when reacting with it

What are the trends of alkali metals? Softness increases as you go down Density increases as you go down Melting point decreases as you go down Reactivity increases as you go down

What happens when the alkali metals react with water?They react violently, giving a hydroxide (alkali) and hydrogen.

Lithium floats and fizzes Sodium shoots across the water Potassium melts and the hydrogen catches fire

What happens when the alkali metals react with chlorine?They burst into flames and burn brightly, forming chlorides.

What happens when the alkali metals react with oxygen?They burn violently, forming oxides which dissolve in water to give alkaline solutions.

Why are the alkali metals so reactive?Because they only need to lose one electron to gain a stable outer shell, so they strongly want to react with other elements in order to lose this electron.

What are the halogens?They are in Group VII in the Periodic Table. They are fluorine, chlorine, bromine and iodine (and astatine).

What are the properties of halogens? Form coloured gases, fluorine is a pale yellow gas, chlorine is a green gas, bromine forms a

red gas and iodine forms a purple gas.

Page | 10

Fadi Munir

Poisonous Form diatomic molecules

What are the trends of the Halogens? The colour gets deeper at room temperature, as you go down Density increases, as you go down Boiling point increases, as you go down Reactivity decreases, as you go down

What are the halogens at room temperature?Fluorine is a yellow gas, chlorine is a green gas, bromine is a red liquid and iodine is a black solid.

How are halides formed?When the halogens react with metals, they form compounds called halides.

Why are the halogens so reactive?Because they only need to gain one electron to gain a stable outer shell, so they strongly want to react with other elements in order to gain this electron.

Write the formula of the reaction of chlorine solution and potassium bromide.2KBr + Cl2 → 2KCl+Br2

When will a halogen displace another?A halogen will displace a less reactive halogen from its halide.

What are the noble gases?The noble gases are the elements of Group 0 in the Periodic Table. They are helium, neon, argon, krypton and xenon (and radon).

What are the properties of the noble gases? Colourless gases that are naturally found in air Form monatomic molecules Absolutely unreactive with anything, which is why they are called noble.

Why are the noble gases unreactive?Because their atoms already have a stable outer shell of electrons so they do not need to react with any other element to gain or lose electrons.

What are the trends of the noble gases? Atoms increase in size and mass, as you go down Density increases, as you go down Boiling points increase, as you go down

What are the uses of the noble gases?The noble gases are unreactive and inert, so they are safe to use; they glow when a current is passed through them. So they have many uses:

Page | 11

Fadi Munir

Helium is used to fill balloons and airships because it is lighter than air, and does not catch fire

Neon is used for neon lighting in signs. It glows red but the colour can be changed by mixing it with other gases

Argon is used as an alternative to air by providing an inert atmosphere, for example in a light bulb where the oxygen in air would cause the filament to burn out

Krypton is used in lasers and in vehicle headlamps Xenon is very bright and used in lighthouses, hospital lights and vehicle headlamps Radon can be used for the treatment of cancer

What are the transition elements?They are the metals in the block in the middle of the Periodic Table, between Group III and Group IV.

What are the transition elements properties? Hard, tough and strong High melting points (except mercury which is a liquid at room temperature) Malleable (can be hammered) Ductile (can be made into wires) Good conductors of heat and electricity High density

How do the transition elements react? Much less reactive than the Group I metals, except for iron which easily rusts Show no trend in reactivity Most form coloured compounds Most form ions with positive charges

What is the valency?The valency of an element is the number of electrons its atoms lose, gain, or share, to form a compound.

What are state symbols?Solid (s), liquid (l), gas (g), aqueous solution (aq)ALWAYS WRITE THE STATE SYMBOLS IN AN EQUATION IN THE TEST

What is the relative atomic mass?It can also be called Ar. And is the mass of an atom compared with the carbon-12 atom.

How do you work out the relative atomic mass of an element with isotopes?First percentage*First nucleon number + Second percentage*Second nucleon numberAnd third, fourth etc.

So, what is the relative atomic mass (Ar) when you have different natural isotopes?The average mass of its isotopes compared to an atom of carbon-12.

What is the relative molecular mass?It is Mr for short, and it is the sum of the relative atomic masses in a molecule. For example, water.

What is the relative formula mass?

Page | 12

Fadi Munir

It is the same as relative molecular mass, also Mr for short, but instead of the sum of relative atomic masses in a molecule, it is in an ion.

Do elements always react in the same ratio?Elements always react in the same ratio, to form a compound. Also, the total mass does not change during a chemical reaction.

What is a mole of a substance?A mole of a substance is the amount that contains the same number of units as the number of carbon atoms in 12 grams of carbon-12. These units can be atoms, molecules, or ions.

What is the Avogadro constant?12g of carbon-12 contain 6.02x1023 carbon atoms.So, 12g of carbon-12 contains 602,000,000,000,000,000,000,000 carbon atoms.So, 602,000,000,000,000,000,000,000 is the Avogadro constant.

So what is the mole measured by?One mole of a substance is obtained by getting the Ar or Mr, of it, in grams.

What is the equation for finding the number of moles in a mass?Number of moles in a mass = mass/mass of 1 mole

What is 1 dm3?1 litre, or 1,000cm3.

What is rtp?Room temperature and pressure. It is the standard conditions for comparing gases. Room temperature is 20oC, and pressure is 1 atm (atmosphere).

What is Avogadro’s Law?1 mole of every gas occupies the same volume at the same temperature and pressure. At rtp, this is 24dm3.

What is the molar volume?The volume occupied by 1 mole of gas. The molar volume of a gas at rtp is 24dm3.

What is the equation for finding the molar volume of a gas?Volume at rtp (dm3) = number of moles*24dm3

What is the concentration of a solution?The amount of solute (in grams or moles) that is dissolved in 1dm3 of solution.Concentration is given in g/dm3 or mol/dm3

What is the equation for finding the concentration in mol/dm3?Concentration (mol/dm3) = amount of solute (mol)/volume of solution (dm3)

What is a hydrocarbon?Substance that contains only hydrogen and carbon atoms.

What is the yield?

Page | 13

Fadi Munir

The amount of product you obtain from a reaction

How do you work out the percentage yield?Actual mass obtained/calculated mass *100%

How do you work out the percentage purity of a product?Mass of the pure product/mass of the impure product obtained *100%

What are the different types of reactions?Neutralisation, precipitation, combustion, displacement, decomposition, and redox reactions.

Explain all the different types of reactions (except redox). Decomposition reactions are reactions where a compound breaks down into two or more

products. H2O H2+O2

Combustion (burning) reactions are special types of redox reactions where oxygen combines with a hydrocarbon to form water and carbon dioxide.CH4 + O2 H2O + CO2

Single displacement reactions are reactions where a single element (more reactive) swaps places with an element in a compound.HCl + Zn ZnCl2 + H2

Double displacement reactions are reactions where an element from each of two compounds swap places. AgNO3 + NaCl AgCl + NaNO3

Neutralisation reactions are special types of double displacement reactions that involve the reaction between an acid and an alkali to form a salt and water.HCl + NaOH NaCl + H2O

Precipitation reactions are aqueous reactions that result in the formation of a precipitate.

What are redox reactions?Oxidation is a gain of oxygen or a loss of electrons, and reduction is a loss of oxygen or a gain of electrons; oxidation and reduction always take place together, in a redox reaction.

Where do we experience redox reactions in our lives?The burning of petrol in our cars is a redox reaction, and respiration taking place in our body is also a redox reaction. Also, electrolysis.

What is oxidation state?Oxidation state tells you how many electrons each atom of an element has gained, lost, or shared, in forming a compound. Oxidation state is usually given as a Roman numeral.

What are the oxidation states?When an element is not combined with other elements, its atoms are in oxidation state 0. Many elements have the same oxidation state in most or all their compounds. But atoms of transition elements can have variable oxidation states in their compounds:Element Common oxidation states in compounds

Page | 14

Fadi Munir

Iron +II and +IIICopper +I and +IIManganese +II, +IV and +VIIChromium +III and +VI

What is a reducing agent?A substance that reduces another substance while oxidising itself.

What is an oxidising agent?A substance that oxidises another substance while reducing itself.

What makes a reducing/oxidising agent strong? And why are they useful? Some substances have a strong desire to gain electrons, so they are strong oxidising agents.

They oxidise other substances by taking electrons from them. For example, oxygen and chlorine.

Some substances have a strong desire to give electrons, so they are strong reducing agents. They reduce other substances by giving electrons to them. For example, hydrogen, carbon monoxide and sodium.

Some oxidising and reducing agents show a colour change when they react, making them useful for lab tests. Such as potassium manganate, potassium dichromate and potassium iodide (reducing).

What is electricity in chemistry?Electricity is a flow of electrons.

How do electrons move through a circuit?The battery releases electrons from the negative terminal. The electrons travel through the wires, bulb and rod, and enter the battery again through the positive terminal.

What is electrolysis?Decomposition caused by electricity is called electrolysis.

Give examples of electrolytes.An electrolyte is a liquid that contains ions, and therefore conducts electricity, is called an electrolyte. Molten lead bromide is an electrolyte.

What happens in the electrolysis of molten lead bromide?1. Electrons flow from the negative terminal of the battery to the cathode2. In the liquid, the ions of the lead bromide (lead and bromide) move to the electrodes of

opposite charge3. At the cathode, lead appears below the cathode, because the positive lead ions accept

negative electrons from the cathode4. At the anode, bromine vapour bubbles off because the negative bromine ions accept positive

electrons from the anode5. Electrons flow from the anode back to the positive terminal of the battery

What are the rules for the electrolysis of an aqueous solution?1. At the cathode, either a metal or hydrogen forms. The more reactive an element is, the more it

wants to stay as an ion. So if a metal is more reactive than hydrogen, it stays as an ion, and hydrogen bubbles off. But if the metal is less reactive than hydrogen, the metal forms.

Page | 15

Fadi Munir

2. At the anode, if the solution is a concentrated solution of a halide, then the halogen forms. But if the halide solution is dilute, or the solution doesn’t contain a halide, oxygen forms.

What is brine?Brine is a concentrated solution of sodium chloride (common salt). It can be obtained by pumping water into salt mines to dissolve the salt, or by evaporating seawater.

What is the equation for the electrolysis of brine?2NaCl + 2H2O 2NaOH + Cl2 + H2

What is a diaphragm cell?A cell whose function is to let ions through but keep the gases apart.

What are the products of brine used for? Chlorine is a poisonous yellow-green gas, used for making plastic, medical drugs, pesticides,

paints, bleaches and hydrochloric acid, and as a sterilising agent to kill bacteria in water supplies and swimming pools.

Sodium hydroxide solution is a corrosive alkali, used for making soaps, detergents, paper, ceramics and medical drugs.

Hydrogen is a colourless, flammable gas, used to make hydrogen peroxide and as a fuel in hydrogen fuel cells.

What is electroplating?Using electricity to coat one metal with another, to make it look better, or to prevent corrosion.

What are exothermic reactions? Give examples.Exothermic reactions give out energy. So there is a temperature rise. The neutralisation of acids by alkalis, the combustion of fuels, respiration in body cells; are examples of exothermic reactions.

Give examples of experiments for exothermic reactions.1. The reaction between iron and sulphur. It needs heat first to start it off, then it glows red hot

without a fire.2. Mixing silver nitrate and sodium chloride, gives a white precipitate of silver chloride and a

temperature rise.3. When you add water to lime (calcium oxide), heat is given out, so the temperature rises.

What are endothermic reactions? Give examples.Endothermic reactions take in energy from their surroundings.

Give examples of experiments for endothermic reactions.1. When barium hydroxide reacts with ammonium chloride, the temperature falls so greatly that

water under the beaker will freeze2. Sherbet is citric acid and the alkali sodium hydrogen carbonate. The neutralisation that occurs

takes in heat, so it cools your tongue when you eat sherbet 3. When heating calcium carbonate, it decomposes to calcium oxide and carbon dioxide.

How is energy in making and breaking bonds?In a reaction, bonds must first be broken, then new bonds are formed. Breaking bonds takes in energy. Making bonds releases energy.

Page | 16

Fadi Munir

How do you get the type of a reaction by the energy of bonds?If the energy taken in to break bonds is less than the energy released in making bonds, the reaction is exothermic. If the energy taken in to break bonds is greater than the energy released in making bonds, the reaction is endothermic.

What is bond energy?The energy needed to break bonds, or the energy released when these bonds form. It is given in kJ/mole.

What is a fuel? And why do we use them?A fuel is any substance used to provide energy. The chemical energy in the fuel is converted into another form of energy. Most fuels are burned to obtain their energy in the form of heat.

What are the fossil fuels?Coal, petroleum (oil), and natural gas (methane) are the main fuels used around the world. They are burned to release heat.

What makes a good fuel? The amount of heat it gives out. As much heat as possible is wanted. The amount of pollution it causes. Its availability. A steady and reliable supply is needed. Its safety. Many fuels catch fire easily, so safety is an issue. Its cost.

What is ethanol as a fuel?Ethanol is an alcohol, C2H5OH. It can be made from any plant material such as sugar cane and corn. It is used in car engines, either on its own or mixed with petrol.

What is hydrogen as a fuel?Hydrogen is a gas that burns explosively in oxygen, giving out a lot of energy, so it is used to fuel space rockets. It is also used in fuel cells without burning, to give energy in the form of electricity.

What are nuclear fuels?Nuclear fuels are fuels that contain unstable atoms called radioisotopes, which break down naturally over time, giving out radiation and a lot of energy. But you can also cause radioisotopes to break down, by shooting neutrons at them. This is what happens in a nuclear power station. The energy given out is used to heat water, which makes steam that drives turbines that generate electricity.

Name a radioisotope.The radioisotope uranium-235 is commonly used in nuclear fuels. When it breaks down, the new atoms it forms are also unstable and break down even further.

What are the advantages and disadvantages of nuclear fuels?Advantages Disadvantages

They give out a lot of energy. An explosion in a nuclear power station could spread radioactive material over a huge area.

Page | 17

Fadi Munir

No polluting gases are formed.

The waste material produced in nuclear power stations is radioactive and can remain very dangerous for many years; so finding a safe place for storage is an issue.

What is a simple cell?A simple cell consists of two metals and an electrolyte. The more reactive metal is the negative pole of the cell. Electrons flow from it.

What are the advantages and disadvantages of the hydrogen fuel cell? No pollutants are formed, only water. The reaction gives out a lot of energy. We will never run out of hydrogen, it can be made by the electrolysis of water. Hydrogen is very flammable, a spark or lit match will cause a mixture of hydrogen and air to

explode.

What is a reversible reaction?A reversible reaction is endothermic in one direction and exothermic in the other direction. The same amount of energy is transferred each time.

What is equilibrium?Equilibrium means there is no overall change. But dynamic equilibrium means there is continual change.

What happens when a reversible reaction is in equilibrium?When a reversible reaction is in equilibrium and you make a change, the system acts to oppose the change, and restore equilibrium.

How does a catalyst speed a reversible reaction?A catalyst speeds up the forward and back reactions equally.

What is rate?Rate is a measure of how fast or slow something is.

In general, how do you find the rate of a reaction?You should measure the amount of a reactant used per unit of time, or the amount a product produced per unit of time.

What is the relation of temperature with the rate of a reaction?A reaction goes faster when the temperature is raised. When temperature increases by 10oC, the rate generally doubles.

What is the relation of surface area with the rate of a reaction?The rate of a reaction increases when the surface area of a solid reactant is increased.

What is the relation of particle collisions with the rate of a reaction?The rate of a reaction depends on how many successful collisions there are in a given unit of time.

Page | 18