Introduction to Physical Chemistry States of matter

Introduction to Physical Chemistry
States of matter: Everything is made of particles and particles in solid are not free to move around but liquids and gases can freely move around. When particles try to move they collide with each other and bounce off in all directions which is called random motion.
In two substances, when mixed, particles bounce off in all directions when they collide. The mixing process is called diffusion, it’s also the movement of particles without a force. The only smallest particle that cannot be broken down by chemical means is called an atom. However in some substances particles are just single atoms. I can easily state one example of a single atom like the gas argon which is found in air and is made up of single argon atom.
Mostly in many substances, particles consist of two atoms joined together which in this case are called molecules. While in other substances particles consist of atoms or groups of atoms that carry a charge and these particles are called ions.
Solids liquids and gases: the Properties of solid are that they are definite in shape and volume and normally hard and rigid hence large force is required to change their shape. They also have a high density and are incompressible. In model solids are closely packed and Occupy minimum space in regular pattern hence vibrate in fixed position but are not free to move.

Properties of liquids are that they have a definite volume but no shape and a high density just like solids not compressible. Their model occur in clusters with molecules slightly further apart as compared to solids and are free to move about within a confined vessel.

We Will Write a Custom Essay Specifically
For You For Only $13.90/page!


order now

Properties of gas are that they have no fixed volume and no fixed shape but with a low density and Compressible. The model of gas is very far apart and travel at high speed which makes it independent and have random motions. Gases have negligible forces of attraction between them.
Diffusion in Gases: gases diffuse in different rates and the rates depend on their factors,
1. Mass of the particles: the lower the mass of its particles the faster a gas will diffuse because the lighter the molecules the faster it will obviously travel.

2. The temperature: the higher the temperature, the faster a gas will diffuse because particles gain energy as they are heated.

Mixtures, Solutions, and Solvents
Mixture: Contains more than one substance therefore they are just mixed together and not chemically combined. Example given can be that of Sand and water.
Solution: It is when a solute and a solvent mix. The solute dissolves in the solvent making a solution. Example given can be that of sugar solute, dissolves in water a solvent making a solution of sugar and water. The solubility of every substance is different and to help a solute dissolve you could stir it or rise the temperature. If you add excess amount of sugar in a small amount of water it won’t dissolve as there is no space for it therefore the solution will become saturated.
Solvent: is a substance that allows solutes to dissolve in and I will give an example of water and ethanol as being solvents and mostly used in science to dissolve solutes.

Pure substances and impurities: a pure substance is a substance that has no particles of any other substance mixed with it, an unwanted substance mixed with a wanted substance is called an impurity and to check if a substance is pure, you have to check its melting and boiling points.
A pure substance has a definite sharp melting point and when a substance is impure the melting point falls and its boiling point rises. So the more impurity present, the wider and bigger the change in melting and boiling point.
Separation methods:
Filter ————————- Solid from liquid
Centrifuge —————— Solid from liquid
Evaporation —————- Solid from its solution
Crystallization ————– Solid from its solution
Distillation —————— Solvent from a solution
Fractional distillation —– Liquid from each other
Chromatography ———- Different substances from a solution
Separation methods
Filtering, for example a mixture of chalk and water can be easily separated by gravity filtration whereby a filter paper is placed in a funnel and the funnel placed on a flask. Then the mixture is poured on the filter paper which is placed on the funnel, then the chalk which in this case is the residue will remain in the filter paper and the water which is the filtrate will fall down in the flask.
Centrifuging this method is used to separate small amounts of solid and liquid. A centrifuge is a machine therefore inside a centrifuge the test tubes are spun very fast so the solid gets flung to the bottom.

Evaporation this method is used to separate a solution in which the solid is dissolved in the liquid. The solution is heated so that the liquid evaporates and the solid remains in the bottom of the evaporating dish.

Crystallization this method is similar to evaporation but here the solid forms crystals then the crystals are left to dry. Separating a mixture of two solids, it can be done by dissolving one in an appropriate solvent, then filtering one and extracting the other from the solution by evaporation.

Simple distillation the first step in this process is that the impure liquid is heated to boiling and steam rises into the condenser then the impurities are left behind. The condenser is cooled so the steam condenses to the pure liquid and it drops out on the beaker, the illustration of the simple distillation process is shown on this diagram under for proper understanding.

Fractional distillation this process is mainly used to separate liquids with different boiling points. The mixture is heated and the wanted and unwanted substances boils and evaporates some of the unwanted liquid will evaporate too and rises up the column. The substance will condense on the beads in the column causing them to heat. When the beads reach a certain temperature when the wanted liquid won’t condense anymore that’s termed to be the boiling point. It will rise while the unwanted liquid will condense and drop. The wanted liquid will make its way through the condenser where it will condense and drop down in the beaker. The illustration of the process is as shown here under;

Chromatography this method is used to separate a mixture of substances for instance you can use it to find how many coloured substances are in black ink.
Steps: the first step is let say to drop the black ink on to the centre of a filter paper and allow it to dry. The next is to drop water on to the ink spot, one drop at a time and suppose there are three rings we say yellow, red and blue, this then shows the ink contains 3 coloured substances.
The substances travel across the paper at different rates and that’s why they separate into rings. The filter paper showing the separate substances is called a chromatogram. This method works because different substances travel at different speeds because they have different levels of attraction to it. Uses of chromatography are to separate mixtures of substances and purifying a substance by separating the impurities from it and the identification of a substance.

The Atoms: are the smallest particles and each atom consists of a nucleus and a cloud of particles called electrons that whizz around the nucleus. An element is a substance that contains only one kind of atom.
The periodic table is the “map/address book” for elements where each element is given a symbol E.g. K for potassium. The group of elements that have similar properties are put in a numbered column. For example, if you know how one element in group 1 behaves, you can easily guess how the others in the same group will behave. The rows are called periods. The zig-zag line separates metals from non-metals, with the non-metals on the right. So most elements are metals.
A compound is said to contain atoms of different elements joined together where the atoms are chemically combined. For example carbon dioxide is a compound of carbon and oxygen 1 carbon and 2 oxygen molecules. The symbol for compound is made from the symbols of the elements in it. So the formula for carbon dioxide is CO2.
Isotopes and Radioactivity atoms can be identified by the number of protons in it. For example, only sodium atoms have 11 protons. Isotopes are atoms of the same element, with different numbers of neutrons. Some isotopes are radioactive. That means its nucleus is unstable sooner or later the atoms breaks down or decays giving out radiation in the form of rays and tiny particles as well as large amount of energy.
Like carbon-14, a number of other elements have radioisotopes that occur naturally and eventually decays. But the other two isotopes of carbon like most natural isotopes are non-radioactive. Decaying of radioisotopes can be known by looking at their half-life. Radiation affects humans as it may cause them radiation sickness but radiation also has some uses.

Uses of radiation: Check for leaks in pipes in industry, this is done by adding a radioisotope to the oil or gas. At a leak, the radiation is detected using an instrument. Radioisotopes used in this way are called tracers. For medicinal we talk of cancer treatment, radioisotopes can cause cancer but yet also can cure it. Using radiotherapy the radioisotope will decay and give out rays that can kill cancer cells. These rays will be aimed exactly at the cancer cells.

To find the age of old remains a tiny percentage of a living thing contains carbon-14 atoms. When living thing dies it no longer takes in new carbon atoms. But existing carbon-14 atom decay over time and we can measure the faint radiation from them.
How electrons are arranged, the electrons in an atom circle fast around the nucleus at different levels from it. These energy levels are called electron shells. The further the shell is from the nucleus, the higher the energy level. Each shell can hold a limited number of electrons. First shell can hold up to 2 electrons Second shell can hold up to 8 electrons the third shell can also hold up to 8 electrons.
Electronic configuration means the arrangement of electrons in an atom. An example to this that of Argon which has the electronic configuration: 2, 8, 8 and Magnesium has the electronic configuration: 2, 8, 2. Important points to note is that the shells fill in order, from lowest energy level to highest energy level. All the elements in a group have the same number of electrons in their outer shells and these are called valency electrons. The group number is the same number of outer shell electrons and the period number shows how many shells there are. If an element possess a full outer shell the element become unreactive.

Atoms combining: Most elements form compounds because they want a full outer shell and to achieve that they must react with other atoms. For example, sodium has just one electron in its outer shell. It can obtain a full outer shell by losing this electron to anther atoms and by that it becomes a sodium ion. Now because sodium lost an electron, it now has 10 electrons but 11 protons so it has a 1 positive charge.
An ion is a charged particle. It is charged because it has an unequal number of protons and electrons.
The ionic bond: an example is Sodium and chlorine react together, sodium gives its electron to chlorine. Now both elements have a full outer shell, but with a charge. Now they are ions. Sodium now has 10 electrons but 11 protons so it has a positive charge. Chlorine now has 18 electrons but 17 protons so it has a negative charge. The two ions have opposite charges so they attract each other. The force of attraction between them is strong and it is called an ionic bond.
When sodium reacts with chlorine, billions and billions of sodium and chlorine ions form and they attract each other. But the ions don’t stay in pairs. They cluster together so that each ion is surrounded by 6 ions of opposite charges. The pattern grows until a giant structure of ions is formed. The overall charge of the structure is 0 since 1 positive charge and 1 negative charge neutralize each other.
The ionic bonding is only between metals and non-metals. Therefore the most important to note is that, hydrogen and the metals form positive ions whilst non-metals form negative ions, and their names end in –ide. Group 4 and 5 do not usually form ions because they would have to lose or gain several electrons and that takes too much energy. Group 0 elements do not form ions because they already have full outer shells. Some of the transition metals form more than one ion. Some ions can be formed from groups of joined atoms and these are called compound ions.

Properties of ionic compound. Ionic compounds have high melting and boiling points. This is because ionic bonds are very strong so it takes a lot of heat energy to break up the lattice. Ionic compounds are usually soluble in water therefore the water molecules can attract the ions away from the lattice and the ions can then move freely, surrounded by water molecules. Ionic compounds can conduct electricity when they are melted or dissolved hence when melted, the lattice breaks up and the ions are free to move. Since they are charged, this means they can conduct electricity. The solutions of ionic compounds conduct electricity too because they are also free to move.
The covalent bond: Giving and losing an electron is not the only way to gain full outer shells since atoms can also share electrons. Covalent bonding is for non-metals only since only non-metals need to gain electrons. A molecule is a group of atoms held together by covalent bonds. When a pair of electrons is shared, it is called a single covalent bond, or just single bond. When 2 pairs of electrons are shared, it is called a double covalent bond, or just double bond. When 3 pairs of electrons are shared, it is called a triple covalent bond, or just triple bond.
A Covalent compound is when atoms of different elements share electrons with each other. The molecules in a covalent compound isn’t flat because each electron repel each other and try to get as far apart from each other.

Molecular substances: mostly these are gases or liquids at room temperature. Molecular solids are held in a lattice but the forces between the molecules are weak and all molecular solids have similar structure. The molecules are held in regular pattern in a lattice. So the solids are crystalline. When you cool down a molecular liquid or gas the molecules lose energy so they start moving slowly and at the freezing point, they form a lattice and a good example to this effect would be ice.
Properties of covalent bonding, the covalent compounds have low melting and boiling point and this is because the forces between the molecules are weak. Covalent compounds do not conduct electricity and this is because molecules are not charged, so they cannot conduct, even when melted.
Giant covalent structures, or macromolecules are made of billions of atoms bonded together in a covalent structure. A good example is diamond it is made of carbon atoms held in a strong lattice. Each carbon atom forms a covalent bond to four others and eventually billions of carbon atoms bond together to form a crystal of diamond.
Properties of diamond are that it is very hard because each atom is held by four strong bonds, it has a very high melting point because of the strong bonds and it can’t conduct electricity because there are no free electrons to carry the charge. Silica is similar to diamond.

Graphite is a very different giant structure like diamond, graphite is made only of carbon atoms. So diamond is and graphite are allotropes of carbon meaning that they are two forms of the same element. Graphite unlike diamond is one of the softest solids on earth. In graphite each carbon atom forms a covalent bond to three others and this gives rings of six atoms.
Properties graphite are that they are soft and slippery because the sheets can slide over each other and they are good conductor of electricity because each carbon atom has four outer electron and graphite bonds 3 only so the fourth electron is free to move carrying a charge.

Substance properties and uses; diamond are hardest known substance, does not conduct electricity and sparkles when cut, they are mainly used in tools for drilling and cutting and for jewellery. Silica is hard and can scratch things and lets light through and has a high melting point, it is mostly used for sandpaper, for making glass and lenses and bricks for lining furnaces. Graphite is soft, slippery, and dark in colour and conduct electricity. It is used as a lubricant for engines for pencil ‘lead’ mixed with clay and for electrodes and connecting brushes in generators. In simple terms to describe the properties of diamond, graphite and silica are as follows; Diamond is hard substance with high melting point and boiling points and cannot conduct electricity. Graphite is soft slippery and good conductor of electricity while Silica has high boiling and melting points and it’s hard.
Metallic bonding: Metals form giant structures in which electrons in the outer shells of the metal atoms are free to move. The metallic bond is the force of attraction between these free electrons and metal ions. Metallic bonds are strong, so metals can maintain a regular structure and usually have high melting and boiling points.
Properties of metals: Metals have high melting points this is so because it takes a lot of heat energy to break up the lattice. Metals are malleable and ductile. Malleable they can be bent and pressed into shapes. Ductile they can be drawn out into wires this is because the layers can slide without the metallic bond breaking, because of this the electrons are free to move too.
Metals are good conductors of heat that is because the free electrons take in heat energy, which makes them move faster and they quickly transfer the heat through the metal structure. Metals are good conductors of electricity this is because the free electrons can move through the lattice carrying the charge. The illustration is given under here:

The Periodic Table, it is a list of all the elements, in order of increasing atomic number. The columns are called groups while the rows are called periods. The group number tells you how many electrons there are in the outer shell of the atoms. The outer-shell electrons are also called valency electrons and their number shows how the elements behave. All elements in a group have similar properties. Group 0 elements have a full outer shell. This makes them unreactive. Some of the groups have special names:
Group 1 – The alkali metals
Group 2 – The alkaline earth metals
Group 7 – The halogens
Group 0 – The noble gases

Trends in the periodic table: The period number gives information about the number of electron shells that are available in that period. Hydrogen sits alone in the table because it is the only element with one electron shell.

The elements in each numbered group shows trends in their properties. For example as you go down group 1, the elements become more reactive or as you go down group 7 the elements become less reactive and so on.
The alkali metals Group 1, their physical properties: Like all metals they are good conductors of heat and electricity and they are softer than most other metals and they have low density. They also have low melting and boiling points, compared to most metals. Their chemical properties are that all alkali metals react vigorously with water, releasing hydrogen gas and forming hydroxides. The hydroxides give alkaline solutions. They react with non-metals. With chlorine they react to make chlorides and with oxygen they make oxides. They form ionic compounds in which the metal ion has a charge of 1+. The compounds are white solids, which dissolve in water to give a colourless solution.
The trend in physical properties
Lithium
Sodium
Potassium
Rubidium
Caesium

Softness

Increases

Density

Increases

Melting
points
decrease

Boiling
points
decreases

The trend in physical properties
Lithium
Sodium
Potassium
Rubidium
Caesium

Softness

Increases

Density

Increases

Melting
points
decrease

Boiling
points
decreases

Why they have similar properties? Because atoms with the same number of valency electrons react in a similar way.

As you go down the group reactivity increase. Because the atoms get larger down the group because they add electron shells.
Group 7: The halogens which is a non-metal group. They Form coloured gases and are poisonous. They are brittle and crumbly in their solid form, and do not conduct electricity. They Form diatomic molecules which means that they exist as 2 atoms.
Trends in their physical properties
Fluorine
Chlorine
Bromine
iodine

Size and
mass of
atom
increases

Density
increases

Melting and
boiling
points
increase

Trends in their physical properties
Fluorine
Chlorine
Bromine
iodine

Size and
mass of
atom
increases

Density
increases

Melting and
boiling
points
increase

Trends in their chemical properties: Reactivity increases as you go up group 7. Because the smaller the atom, the easier it is to attract the electron so the more reactive the element will be. They are so reactive because their atoms are only one electron short of a full shell.
Group 0: The noble gases are non-metal group and contains colourless gases, which occur naturally in air they are monatomic which means that they exist as single atoms and are unreactive because they have a full outer shell.
Trends in their physical properties
Helium
Neon
Argon
Krypton
Xenon

Uses of noble gases

Size and
mass of
atom
increases

Density of
gas
increases

boiling
points
increase
Helium
Neon
Argon
Krypton
Xenon

Uses of noble gases

Size and
mass of
atom
increases

Density of
gas
increases

boiling
points
increase
Noble gases are unreactive, making them safe to use. They also glow when current is passed through them at low pressure.
Gas Use
Helium -Used to fill balloons and airships, because it is much lighter than air and will not catch fire
Neon -Used in advertising signs. It glows red, but the colour can be changed by mixing it with other gases.

Argon -Used as a filler in ordinary tungsten light bulbs. (oxygen would make the tungsten filament burn away)
-Used to protect metals that are being welded. It won’t react with the hot metals (unlike oxygen)
Krypton -Used in lasers. For example for eye surgery and in car headlamps
Xenon -Used in lighthouse lamps, lights for hospitals operating theatres, and car headlamps.

The transition elements: The transition elements are the block of 30 elements in the middle of the periodic table and they are all metals. The following are their physical properties, they are hard, tough and strong, they have high melting points except for mercury. They are Malleable and ductile and are Good conductors of heat and electricity and have High density.
Their chemical properties are as follows, they are much less reactive than the metals of group 1. They show no clear trend in reactivity, unlike the metals of group 1. Most transition metals form coloured compounds. Most of them can form ions with different charges, they have variable valency. They can form more than one compound with another element. Most transition metals can form complex ions.
Uses of transition metals: The hard strong transition metals are used in structure such as bridges, buildings, cars etc. Many transition metals are used in making alloys. Transition metals are used as conductors of heat and electricity. Many transition metals and their compounds act as catalysts
Chemical equations
Physical and chemical change: A substance can be changed by heating it, adding water to it, mixing another substance with it, and so on. The change that takes place will be either chemical change or a physical change.
Chemical change: In a chemical change, a new chemical substance is produced.
The difference between a mixture and a compound, In a Mixture 2 substances are mixed together but not chemically bonded. In a Compound, 2 substances are chemically bonded together: The signs of a chemical change, a chemical change is usually called a chemical reaction. You can tell when a chemical reaction has taken place by these signs:
Once or more new chemical substances are formed, the new substance usually looks different from the starting substances.
Energy is taken in or given out during the reaction. A change that gives out heat energy is called exothermic and a change that takes in heat energy is called endothermic.
The change is usually difficult to reverse, this means it will be hard to get back the raw materials of the reaction.
Physical change: If no new chemical substance is formed, a change is a physical change. Equations for chemical reactions: The reaction between carbon and oxygen. When they react together, they form carbon dioxide. Carbon and oxygen are the reactants. Carbon dioxide is the product of the reaction.

3869690-157298O
O
C

O
O
C

C 235585-1985631802130-200468 + O O ?

1 atom of carbon 1 molecule of oxygen 1 molecules of carbon dioxide
Or in a shorter way, using symbols and numbers like this:
C + O2 ? CO2
This short way to describe the reaction is called a chemical equation. The reaction between hydrogen and oxygen:
H

H

H

H

O

O

H

H

O

H

H

O

+

?
H

H

H

H

O

O

H

H

O

H

H

O

+

?

2 molecules of hydrogen 1 molecules of oxygen 2 molecules of water
And the equation is:
2H2 + O2 ? 2H2O
On the left same as on the right, so:
On the left:
4 hydrogen atoms
2 Oxygen atoms ? On the right:
4 hydrogen atoms
2 Oxygen atoms

You can show the state of the reactants and products by adding state symbols to the equation: – (s) for solid
– (l) for liquid
– (g) for gas
– (aq) for aqueous solution (solution in water)
Acids and alkalis: For acids you can tell if something is acid, by its effect on litmus. Litmus is a purple dye and it can be used as a solution, or on paper. Acids turn litmus red. For alkali you can tell if something is alkali by its effect on litmus. Alkali turn litmus blue. Litmus is called an indicator, because it indicates whether something is an acid or an alkali. Many substances are not acids or alkalis. They are neutral. Example of neutral substances is pure water.
You can say how acidic or alkaline a solution is using a scale of numbers called the pH scale. The numbers go from 0 to 14: illustration of the same is given on this chart under

On this scale: An acidic solution has a pH number less than 7, an alkaline solution has a pH number greater than 7 and a neutral solution has a pH number of exactly 7. Acidic solutions contain hydrogen ions and this is what makes them ‘acidic’ in short Acids produce hydrogen ions.

The difference between strong and weak acids, in solution of strong acids, all molecules become ions while in solution of weak acids only some do. The higher the concentration of hydrogen ions, the lower the pH and the stronger the acid. Alkaline solutions contain hydroxide ions and this is what makes them alkaline. Alkalis produce hydroxide ions in solution of strong alkali and it contains more hydroxide ions.
The difference between a strong alkali and weak alkali, in solution of weak alkali it contains less hydroxide ions. The higher the concentration of hydroxide ions, the higher the pH. To tell if the solution is a weak or strong acid. You can also measure there conductivity. A strong acid will show high conductivity and low pH. A weak acid does not conduct well and has a higher pH. For alkali’s, a strong alkali will show high conductivity and high pH. A weak acid will show low conductivity and low pH.
Reaction of acids with metals when an acid reacts with a metal, hydrogen is displaced, leaving a salt in solution. It’s a redox reaction. Reaction of acids with bases, Bases are a group of compound that reacts with acids, and neutralize them, giving a salt and water. Bases include alkalis, and insoluble metal oxides, hydroxides and carbonates.
1. with alkalis: Acid + alkali ? salt + water
2. with metal oxides: Acid + metal oxide ? salt + water
3. with carbonates: Acid + metal carbonate ? salt + water + carbon dioxide
Reactions of bases: Neutralizing acids, giving salt and water. With carbonates carbon dioxide is produce too. All the alkalis except ammonia will react with ammonium compounds, giving ammonia out.
The ionic equation: An ionic equation shows only the ions that actually take part in a reaction but leaves out the rest. First write down all the ions present in the equation, now cross out any ions that appear, unchanged on both sides of the equation. What is left is the ionic equation for the reaction.
Proton donors and acceptors: Acids donate its protons to bases and bases accept them.
For example: Magnesium oxide is an insoluble base. The acid donates its H+ protons and the oxygen from magnesium oxide react with it to make water molecules.
Acidity in soil: Most crops grow best when the pH of the soil is near 7. If soil is too acidic or too alkaline, crops grow badly or not at all. Usually acidity is the problem because of a lot of vegetation rotting in it or because too much fertilizer was used in the past. To reduce the acidity the soil is treated with a base like limestone or quicklime or slaked lime.
Acid rain: Acid rain is caused by factories, power stations, homes who burn fossil fuels to make electricity. The waste gases from all these reactions include sulphur dioxide, and oxides of nitrogen. They go into the air and react with air and water to produce sulphuric acid and nitric acid which are strong acids.
Making salts: You can make salts by reacting metals, insoluble bases, or soluble bases with acids. With metals for example: Add the zinc to the sulphuric acid in a beaker and it will start to dissolve and hydrogen bubbles are given off. Stops when all the acid is used up. Excess zinc is removed by filtering, this leaves an aqueous solution of zinc sulphate. The solution is then heated to evaporate some water. Thereafter it is left to cool and crystals of zinc sulphate start to form.
With insoluble base: It’s the same method as the one above but, the metal won’t react with the acid. So you must start with a metal oxide. With an alkali (soluble base):
1. Put the alkali into a flask and add some drops of indicator
2. Add the acid from a burette, just a little at a time. Swirl the flask to help the acid and alkali mix.
3. When the indicator turns green stop adding acid.
4. Calculate how much acid was used.
5. Carry out the experiment again without the indicator and add same amount of acid that was used before. This is because the indicator will make the salt impure.
6. Heat the solution from the flask and crystals will start to form.

Making insoluble salts by precipitation: Not all salts are soluble.
Soluble Insoluble
All sodium, potassium, and ammonium salts All nitrates Chlorides… Except silver and lead chloride
Sulphates… Except calcium, barium and lead sulphate
Sodium, potassium, and ammonium carbonates… But all other carbonates are insoluble.

Insoluble salts can be made by precipitation
Preparing barium sulphate: Barium sulphate is an insoluble salt. You can make it by mixing solutions of barium chloride and magnesium sulphate.
1. Make up solutions of barium chloride and magnesium sulphate.
2. Mix them. A white precipitate of barium sulphate forms at once.
3. Filter the mixture. The precipitate is trapped in the filter paper.
4. Rinse the precipitate by running distilled water through it.
5. Then place it in a warm oven to dry
To precipitate an insoluble salt, you must mix a solution that contains its positive ions with one that contains its negative ions.
How fast reactions are: Some reaction are fast and some are slow. What is rate?
Rate is a measure of how fast or slow something is or rather Rate is a measure of the change that happens in a single unit of time and to find rate of a reaction, you should measure, the amount of a reactant used up per unit of time or the amount of a product produced per unit of time.

A reaction that produces a gas: When you react magnesium and hydrochloric acid, it produces hydrogen gas. To measure the rate of this reaction this method is set up:

Stop clock

Stop clock

Using this you can measure the amount of hydrogen produced in a period of time.
Collisions: For a chemical reaction to occur, the reactant particles must collide. But collisions with too little energy do not produce a reaction. The particles must have enough energy for the collision to be successful in producing a reaction. The rate of reaction depends on the rate of successful collisions between reactant particles. The more successful collisions there are, the faster the rate of reaction.
Changing the temperature: If the temperature is increased the reactant particles move more quickly and they have more energy thereby the particles collide more often, and more of the collisions result in a reaction and the rate of reaction increases.
Changing the concentration or pressure: If the concentration of a dissolved reactant is increased, or the pressure of a reacting gas is increased the reactant particles become more crowded and there is a greater chance of the particles colliding and the rate of reaction increases.
Changing the surface area: If a solid reactant is broken into small pieces or ground into a powder its surface area increases and more particles are exposed to the other reactant hence there are more collisions and the rate of reaction increases.
The effect of light: Some chemical reactions obtain the energy from light and they are called photochemical reactions. For example:
1. Silver bromide is pale yellow, but darkens on exposure to light because the light causes it to decompose to silver: 2AgBr ? 2Ag + Br2
2. Plants use carbon dioxide from the air to make sugar called glucose, in a reaction called photosynthesis. This uses the energy in sunlight. The green substance – chlorophyll – in leaves speeds up the reaction: 6CO2 + 6H2O ? C6 H12 O6 + 6O2
Carbon dioxide + water ? glucose + oxygen
In both these reaction, the stronger the light, the more energy it provides so the faster the reaction goes.
Effect of catalysts: A catalyst is a substance that can increase the rate of a reaction. The catalyst itself remains unchanged at the end of the reaction it catalyses. Only a very small amount of catalyst is needed to increase the rate of reaction between large amounts of reactants.
A catalyst works by lowering the activation energy for the reaction.
Enzymes: biological catalysts, enzymes are proteins that act as catalysts. So they are often called biological catalysts. How enzymes work: First the enzyme and the reactant molecule fit together like jigsaw pieces. The reactant molecule has to be the right shape. The enzyme breaks down the molecule to smaller pieces and so on.
Important notes: An enzyme works best in conditions that match those in the living cells it came from. This means most enzymes work best in the temperature range 25-45ºC. If the temperature is too high, an enzyme loses its shape and it becomes denatured. An enzyme also works best in a particular pH range.
Uses of enzymes: they are used in making ethanol making bread and in biological detergents.
The behaviour of metals: Most elements are metals. Properties of metals: They are strong. 2. They are malleable 3. They are ductile 4. They are sonorous, they make a ringing noise when you strike them. 5. They are shiny when polished 6. They are good conductors of electricity and heat 7. They have high melting and boiling points they are all solid at room temperature, except mercury. 8. They have high density, they are heavy. 9. They react with oxygen to form oxides 10. When they react, metals form positive ions.
The last two properties are chemical properties, the others are physical properties.
Metals reactivity: A reactive element has a strong drive to become a compound. So it reacts readily with other elements and compounds. If a metal is more reactive than another metal, then it displaces it and takes its place. For example: When a metal is heated with an oxide of a less reactive metal, it acts as a reducing agent. The reaction always gives out heat – it is exothermic. Reducing agent: is a substance which brings about the reduction of another substance.
A metal will always displace a less reactive metal from solutions of its compounds.

The reactivity series:
Potassium, K
Sodium, Na
Calcium, Ca
Magnesium, Mg
Aluminum, Al
Carbon
Zinc, Zn
Iron, Fe
Lead, Pb
Hydrogen
Copper, Cu
Silver, Ag
Gold, Au
Increasing
Reactivity
Most reactive

Least Reactive

Metals above the red line: They displace
hydrogen from acids, and hydrogen
can’t reduce their oxides.
Metals above the blue line: Carbon
can’t reduce their oxides.
Potassium, K
Sodium, Na
Calcium, Ca
Magnesium, Mg
Aluminum, Al
Carbon
Zinc, Zn
Iron, Fe
Lead, Pb
Hydrogen
Copper, Cu
Silver, Ag
Gold, Au
Increasing
Reactivity
Most reactive

Least Reactive

Metals above the red line: They displace
hydrogen from acids, and hydrogen
can’t reduce their oxides.
Metals above the blue line: Carbon
can’t reduce their oxides.

Things to remember about the reactivity series: The reactivity series is a list of metals in order of their drive to form positive ions. The more reactive the metal, the more easily it gives up electrons to form positive ions.
A metal will react with a compound of a less reactive metal for example an oxide by pushing the less reactive metal out of the compound and taking its place, as ions.
The more reactive the metal, the more stable its compounds are. The more reactive the metal, the more difficult it is to extract it from ores. The less reactive the metal, the less it likes to form compound.
The stability of some metal compounds: Many compounds break down easily on heating. In other words, they undergo thermal decomposition. Thermal decomposition is the breakdown of a compound by heating it.
Carbonates: Most decompose to oxide and carbon dioxide, on heating. But the carbonates of potassium and sodium do not decompose. Strong heating is needed to break down calcium carbonate and the reaction is reversible. The further down the series, the more easily the other carbonates break down. For example Copper (II) carbonate breaks down very easily, like this:
CuCO3 (s) ? CuO (s) + CO2 (g)
Hydroxides: Most decompose to oxide and water on heating, like this:
Zn (OH) 2 (s) ? ZnO (s) + H2O (l)
But the hydroxide of potassium and sodium do not decompose. The further down the series, the more easily the others break down.
Nitrates: All decompose on heating – but not all the same products. Potassium and sodium nitrates break down to nitrites, releasing only oxygen, like this:
2NaNO3 (s) ? 2NaNO2 (s) + O2 (g)
But the nitrates of the other metals break down further to oxides, releasing the brown gas nitrogen dioxide as well as oxygen:
2Pb (NO3)2 ? 2bO (s) + 4NO2 (g) + O2 (g)
The further down the series, the more easily they break down
Uses of reactivity series: The thermite process. The sacrificial protection of iron. Galvanizing. Making cells (batteries)
Making use of metals: Metal Ores, Sodium = rock salt, Aluminium = bauxite, Iron = hematite.
Extraction Method of extraction
Potassium, K
Sodium, Na
Calcium, Ca
Magnesium, Mg
Aluminum, Al
Carbon
Zinc, Zn
Iron, Fe
Lead, Pb
Hydrogen

Copper, Cu
Silver, Ag
Gold, Au
Least Reactive

Increasing
Reactivity

Most reactive

Ores more
difficult to
decompose

Method of
extraction
more difficult

Method of
extraction
more
expensive
Electrolysis

Heating with
a reducing
agent (carbon
or carbon
monoxide
Occur
naturally
as elements. So
no chemical
reaction is
needed. Only
separation from
impurities

Potassium, K
Sodium, Na
Calcium, Ca
Magnesium, Mg
Aluminum, Al
Carbon
Zinc, Zn
Iron, Fe
Lead, Pb
Hydrogen

Copper, Cu
Silver, Ag
Gold, Au
Least Reactive

Increasing
Reactivity

Most reactive

Ores more
difficult to
decompose

Method of
extraction
more difficult

Method of
extraction
more
expensive
Electrolysis

Heating with
a reducing
agent (carbon
or carbon
monoxide
Occur
naturally
as elements. So
no chemical
reaction is
needed. Only
separation from
impurities

Extraction of zinc from zinc blende: Zinc blende is mainly zinc sulphide, ZnS. First it is roasted in air, giving zinc oxide:
Zinc sulphide + Oxygen ? Zinc oxide + Sulphur dioxide
2ZnS (s) 3O2 2ZnO (s) 2SO2
Then the oxide is reduced in one of the two ways below:
Using carbon monoxide. This is carried in a furnace:
Zinc oxide + Carbon monoxide ? Zinc + Carbon dioxide
ZnO (s) CO (g) Zn (s) CO2 (g)
The final mixture contains zinc and a slag of impurities. The zinc is separated from it by fractional distillation. (It boils at 907ºC)
Using electrolysis: Extraction of iron
The blast furnace

The reactions in the blast furnace: Stage 1: The coke burns giving off heat, the blast of hot air starts the coke burning. It reacts with the oxygen in the air, giving carbon dioxide:
Carbon + Oxygen ? Carbon dioxide
C (s) O2 (g) CO2
Explanation: It’s a combustion reaction which means it’s a redox reaction. The carbon is oxidized to carbon dioxide. The blast of air provides the oxygen for the reaction. The reaction is exothermic – it gives off heat, which helps to heat the furnace.
Stage 2: Carbon monoxide is made: The carbon dioxide reacts with more coke, giving carbon monoxide:
Carbon + Carbon dioxide ? Carbon monoxide
C (s) CO2 (g) 2CO (g)
Explanation: In this redox reaction, the carbon dioxide loses oxygen. It is reduced. The reaction is endothermic – it takes in heat from the furnace. This is good because stage 3 needs a lower temperature.
Stage 3: The iron (III) oxide is reduced: This is where the actual extraction occurs. Carbon monoxide reacts with the iron ore giving liquid iron:
Iron (III) oxide + Carbon monoxide ? Iron + Carbon dioxide
Fe2O3 (s) 3CO (g) 2Fe (l) 3CO2 (g)
The iron trickles to the bottom of the furnace.
Explanation: In this redox reaction, carbon monoxide acts as the reducing agent. It reduces the iron (III) oxide to the metal. At the same time the carbon monoxide is oxidized to carbon dioxide.

What is the limestone for? The limestone reacts with the sand (silica) in the ore, to form calcium silicate or slag.
Limestone + Silica ? Calcium silicate + Carbon dioxide
CaCO3 (s) SiO2 (s) CaSiO3 (s) CO2 (g)
The slag runs down the furnace and floats on the iron.
Explanation: The purpose of this reaction is to remove impurities from the molten iron. Silica is an acidic oxide. Its reaction with limestone is neutralization because limestone is a base, giving calcium silicate, a salt.
The waste gases: These are carbon dioxide and nitrogen. They come out at the top of the furnace.
Explanation: The carbon dioxide is from the reduction reaction in stage 3. The nitrogen is from the air blast. It has not taken part in the reactions so has not been changed.
The molten iron is tapped from the bottom. It is impure with carbon as the main impurity. Some is run into moulds to give cast iron. This is hard but brittle. But most of the iron is turned into steel.

Uses of some metals:

Steel and other alloys: An alloy is a mixture of metals that changes there properties or increase them. Turning a metal into an alloy increases its range of uses. Pure iron is too soft and stretches easily and rusts. When carbon (0.5%) is mixed with it, the result is mild steel. This is hard and strong.
Uses of mild steel: buildings, ships, car bodies and machinery, when nickel and chromium are mixed with iron, the result is stainless steel. This is hard and rustproof.
Uses of stainless steel: car parts, kitchen sinks and cutlery.

Making steels: This is how steels are made, first, unwanted impurities are removed from the iron. The molten iron from the blast furnace is poured into an oxygen furnace. Calcium oxide is added, and a jet of oxygen is turned on. The calcium oxide neutralizes any acidic impurities, forming a slag that is skimmed off. The oxygen reacts with the others burning them away.

Then other elements may be added, this is measured out carefully, to give steels with the required properties.

Corrosion: this is when a metal is attacked by air, water, or other substances in its surroundings, the metal is said to corrode. The more reactive a metal is, the more readily it corrodes.
What does rusting involve? Rusting needs both air and water, as these tests show

How to prevent rusting, Coat the metal with something to keep out air and moisture. You could use: – Paint – Grease – Plastics – Another metal. For example:
Zinc: by dipping iron into molten zinc. This is called galvanizing. Tin: deposited on the steel by electrolysis, in a process called tin plating. Chromium: coating with chromium. The chromium is deposited by electrolysis.
Use sacrificial protection: This is when a more reactive metal is attached to the metal and it corrodes instead of the steel. This is called sacrificial protection.
Does aluminium corrode? No, because a coat of aluminium oxide forms on the aluminium which acts as a seal preventing corrosion.

Unit 14: Air and water: Air is a mixture of gases.

These can be separated by fraction distillation. This works because the gases in air have different boiling points.

Uses of oxygen: In hospitals People with breathing problems are given oxygen through oxygen tanks covering the nose and mouth, they also use oxygen tents. Welding metals: A mixture of oxygen and ethanol is used in oxy-acetylenes torches for that are used in welding metals.

Air pollutants:

Ways to reduce pollution: Use less fossil fuels, Switch to clean sources of power and try to find ways to store CO2 and not let it escape to the atmosphere
Catalytic converters: An exhaust pipe is a pipe where waste gases are disposed off. In it, harmful gases are present:

Uses of water: At home for drinking, cooking, washing things and flushing toilet waste away. On farms it is needed as a drink for animals and to water crops. In industry they use it as a solvent and to wash things and to keep hot reaction tanks cool. Power stations use it to make steam. The steam then drives the turbines that generate electricity.

Purifying water

Chemical tests for water: It turns white anhydrous copper (II) sulphate blue.
It turns blue cobalt chloride paper pink.

Organic chemistry is a branch of chemistry connected with compounds of hydrogen and carbon (hydrocarbons).
Hydrocarbons: It is a class containing only hydrogen and carbon bonded together covalently. They can form very long chains, and can form chains linked by one double bond or triple bond. Hydrocarbons are divided into two groups Alkanes C-C and Alkenes C=C
Naming of organic substances
1C -> meth 3C -> prop 5C -> pent 7C-> hept 2C -> eth 4C -> but 6C -> hex 8C -> hex

Alkanes: General molecular formula = Cn H2n+2 the alkanes are a homologus series which means that all of the compound have the same.
Functional group, same general formula, same chemical properties, show a gradual change in chemical properties.

x

Hi!
I'm Heidi!

Would you like to get a custom essay? How about receiving a customized one?

Check it out