Matter is anything which has mass and takes up space. There are three states of matter, solid, liquid, and gas.
Solid - definite shape, definite volume, does not flow. Particles vibrate only.
Liquid - no definite shape, definite volume, can flow. Particles slide over each other.
Gas - no shape, no definite volume, can be compressed. Particles are move freely.
Changes of state due to heating. Melting happens when a solid is
heated until it becomes a liquid.
Evaporation happens when a liquid becomes a gas on the surface only.
Boiling point is the temperature at which a liquid becomes a gas throughout the whole liquid.
Changes of state due to cooling.
Freezing happens when a liquid is cooled until it becomes a solid.
Condensation happens when a gas is cooled until it becomes a liquid.
Experiment; To separate salt and water ( by evaporation)
Boil the salty water until the basin is almost dry. Turn off the Bunsen and allow the hot basin to sit. The remaining water should evaporate off, leaving the salt in the basin.
States of matter and Separation techniques
Experiment;To separate sand and salt
1. Dissolve the sand and salt in water in a beaker. 2. Filter off the sand.
3. Then boil off the water in an evaporating dish.
Experiment; To separate a mixture of dyes by chromatography.
The solvent will soak up along the paper carrying the dye with it.
The colours in the mixture will travel at different speeds up the paper because some are more soluble in the solvent than others.
Eventually, all the colours will separate from each other.
Place the copper sulphate solution in the round-bottom flask.
Heat until the solution starts to boil. As the water evaporates (changes from a liquid to a gas) it leaves the flask through the condenser’ as steam.
The condenser has a ‘jacket’ of cold water constantly flowing around its outer section. This causes the steam to condense back into liquid water.
The water collected in the flask on the right is called the distillate.
Experiment; To separate copper
sulfate from water
Experiment; To separate soil and water by filtration
Filter funnel
filtrate
Soil and water The particles are held
Gases present in air Nitrogen Element 78%
Oxygen Element 21%
Carbon dioxide Compound 0.03%
Water vapour Compound 1 – 4%
Noble gases Elements < 1%
Air is a mixture because;
1.The gases can be separated by physical means.
2.The gases in the air behave independently. 3.The composition of the air varies from
place to place.
Experiment 1;To show that the air contains 21% oxygen gas
gas syringe A containing 100ml of air.
gas syringe B copper
metal
The air is passed continuously from syringe A to syringe B.
The copper reacts with the oxygen in the air and forms copper oxide.
This removes the oxygen from the air.
Since 21ml of air is removed this portion of the air must be oxygen.
Therefore, the percentage oxygen in the air is 21%.
Experiment 2; To show that the air contains 21% oxygen gas
At the start, there are 100ml of air in the graduated cylinder.
As the candle burns, the oxygen is used up.
This creates a vacuum and water is sucked in from outside to replace the oxygen used.
Only, approximately, 80 ml of gas remain.
Therefore the oxygen must have occupied 20mls of the air.
Experiment 3;To show that air contains both water vapour and carbon dioxide
air in air out
ice water blue cobalt chloride
paper
As air is drawn through the first flask water vapour in the air condenses into liquid because it is so cold.
The water will turn the blue cobalt chloride to pink, this the standard test for the presence of water.
As the air bubbles through the limewater the carbon dioxide in the air will turn it milky white.
Uses of Oxygen gas
1. Breathing apparatus. 2. Welding.
3. Rocket fuel. 4. Steel manufacture.
Experiment 5; Burning some magnesium metal in oxygen
Place some magnesium on a deflagrating spoon. Heat it in a Bunsen burner until it starts to spark. Place it in a jar of the oxygen just collected. It will burn extremely brightly until all of the oxygen has been used up.The jar now contains magnesium oxide.
Test this by some damp red litmus paper. It will turn it blue, indicating that MgO is a base.
Experiment 5; Burning some carbon in oxygen
Place some charcoal on a deflagrating spoon. Heat it in a Bunsen burner until it starts to glow.
Place it in a jar of the oxygen just collected. It will burn extremely brightly until all of the oxygen has been used up.The jar now contains carbon dioxide.
Test this by adding limewater to the jar and shaking. It will go milky white.
Experiment 4; Preparation of Oxygen gas
A Catalyst is a substance which speeds up a reaction without getting used up itself.
gas
oxygen
water
peroxide
hydrogen
MnO 2 22
2
O
2
H
O
O
H
2
2Physical properties
1. Colourless, odourless, tasteless gas 2. Slightly soluble in water
3. Denser than air
Chemical properties
1. Supports combustion 2. Reacts with most elements 3. It has no effect on litmus
Hydrogen peroxide
Oxygen
Preparation of carbon dioxide gas.
The equation for the reaction is; dioxide chloride acid carbonate carbon water calcium ic hydrochlor calcium CO O 2H CaCl 2HCl
CaCO3 2 2 2
Physical Properties
1. Colourless, odourless, tasteless gas 2. Slightly soluble in water
3. Denser than air
Chemical properties
1. Does not support combustion (puts out a lighting splint).
2. Turns limewater milky 3. Turns litmus red (acidic)
Uses of carbon dioxide
1. Fizzy drinks. 2. Fire extinguishers. 3. By plants in photosynthesis.
4. Dry ice (solid carbon dioxide) for cold storage.
Tests on carbon dioxide gas
1. Carbon dioxide turns limewater milky white.
Bubble the gas through a test tube of limewater. It will go milky white. The equation for this is,
carbonate dioxide water calcium carbon limewater O H CaCO CO
Ca(OH)2 2 3 2
2.Carbon dioxide turns litmus red.
Bubble some carbon dioxide gas through blue litmus solution and it will turn red.
Solutions
A solution is a mixture of a solute dissolved in a solvent.
A solute is a substance which is being dissolved.
A solvent is a substance which allows other substances to dissolve in it.
A saturated solution is a solution which has dissolved as much solute as possible, at a given temperature. The amount dissolved can be increased by increasing the temperature.
A concentrated solution is one where a large quantity of solute has been dissolved in a small quantity of solvent. Note;To make the solution more concentrated you can,
Dissolve more solute (copper sulphate crystals) or,
Boil off some of the solvent (water).
A dilute solution is one where a small quantity of solute has been dissolved in a large quantity of solvent.
To make a solution more dilute add more solvent to the solution (water).
Examples of solutions
Salt dissolved in water. Sugar dissolved in water. Tea dissolved in water.
Air dissolved in sugar (marshmallow).
A suspension is when a solid breaks up into fine particles which spread out in a liquid but do not dissolve in it.
Examples of suspensions
Soil in water (mucky water)
Milk contains tiny particles of milk which are
not dissolved in water.
100 g of water in the conical flask was brought to the required temperature using the water bath.
Copper sulfate crystals were added to the water until no more would dissolve. The mass of the copper sulfate crystals that dissolved was noted.
The temperature was then increased in stages and the mass of the copper sulfate crystals that dissolved was noted each time.
A graph similar to the one below should be obtained.
Experiment; To investigate the effect of temperature on solubility.
Experiment; To make a solution of copper sulphate and grow copper sulphate crystals
Add a small quantity of copper sulphate to some water in a beaker and stir well to dissolve.
This is a solution of copper sulphate.
The water is the solvent.
The copper sulphate is the solute.
Continue to add more copper sulphate until no more will dissolve. This is a saturated solution of copper sulphate.
Heat the beaker gently and you will find that you can get more to dissolve.
An atom is the smallest part of an element which still retains the properties of that element.
An element is substance which cannot be broken into simpler substances by chemical means
.
Metals
Zinc Zn Grey metal
Aluminium Al Silver grey
Iron Fe Silver grey
Silver Ag ‘Silver’
Gold Au Shiny
Non-metals
Chlorine Cl Green gas
Carbon C Black soot
Oxygen O Invisible gas Sulphur S Yellow solid Hydrogen H Invisible gas Nitrogen N Invisible gas
A compound may be defined as a substance which contains two or more elements chemically combined. A molecule is the smallest part of an element or compound which can exist on its own.
Examples of compounds
Carbon dioxide (CO2), Water (H2O), Methane (CH4),Ammonia (NH3)
A Mixture is two or more substances mixed but not chemically combined.
Examples of mixtures
Seawater is a mixture of water and salt.
Soft drinks are mixtures of water, sugar, flavourings, colours and preservatives.
Tea is a mixture of water, sugar, tea, and milk.
Air is a mixture of nitrogen gas, oxygen gas and others.
Differences between a compound and a mixture .
Mixture Compound
Make-up Varies Fixed
Heat change
None Heat in
Formation
Separate Easy Difficult
Properties Same as constituents
New properties
Experiment; To show the difference between a mixture and a compound.
1. When the yellow sulphur is just mixed with the iron filings, the mixture can be separated easily with a magnet. 2. But when heated they combine chemically to form a new
substance which cannot be separated with a magnet. 3. The new substance is a grey compound and is called Iron
Sulphide.
The Periodic Table of Elements is a table which lists all of the known elements in order of increasing atomic number.
The table is divided into eight groups. The groups are numbered with Roman numerals (I, II, III, IV, V, ….) Group I is called alkali metals.
Group II is called alkaline earth metals.
Group VII is called halogens.
Group VIII is called inert gases or noble gases.
The block of elements in the middle of the table is called the ‘Transition metals’.Atoms, elements, compounds
and the periodic table
The Atom
Name Found Mass [amu] Charge
Proton Nucleus 1 +1
Neutron Nucleus 1 0
Electron Cloud 1/1850 - 1
Example; Draw an atom of sodium given the following information, 1123
Na
+
Rules for drawing an atom
1. Atomic Number is the number of protons in the nucleus of an atom. This number is the smaller number given in the PTE
2. Mass number is the number of protonsand neutrons in the nucleus of an atom. This number is the bigger number beside the element in the P.T.E. 3. Number of protons = number of electrons in a
neutral atom.
4. The electrons are arranged in circular shells around the nucleus. 2 in the 1st , 8 in all the others.
Example 1; Describe the ionic bond in Sodium Chloride, NaCl.
Because it gained an electron Cl is now a negatively charged Cl- ion.
Sodium has lost an electron so it will be a positively charged Na+.
The positive Sodium and the negative Chloride ion are attracted to each other and form a very strong bond.
This is an ionic bond.
An Ionic bond is the force of attraction between oppositely charged ions in a compound.
An ion is a charged atom or group of atoms.
Octet rule – ‘When an atom forms a chemical bond it will attempt to gain eight electrons in its outer shell (or at least a full outer shell).Example 2;
Describe the ionic bond between magnesium and oxygen in magnesium oxide, MgO.
Answer;
Magnesium has 12 electrons, 2 in the first shell, 8 in the second shell and 2 in the third.
Oxygen has 8 electrons, 2 in the first shell and 6 in the second.
If magnesium loses its two outer electrons the third shell doesn’t exist anymore.
The second shell is now the outer shell and this has eight electrons, which is very stable.
Because the magnesium atom has lost two electrons it now has a +2 charge. It is now called an ion (charged atom).
The oxygen has gained two electrons and now has eight electrons in the outer shell, which makes it stable.
It has gained two electrons and has a -2 charge. It is nowcalled an oxide ion.
Experiment; To investigate the ability of ionic and covalent compounds to conduct electricity.
1. Place a variety of liquids in the beaker and record whether or not the bulb lights.
2. Any solution which allows the bulb to light and any which does not is covalent.
bulb battery
electrodes
Ionic compounds
1. They are solids because of the great attraction between the ions. 2. They have high melting points and
boiling points.
3.
They are soluble in water. Water molecules are attracted them.4.
They conduct electricity when melted or dissolved in water.Covalent compounds
1. They consist of separate molecules.
2. They are usually liquids or gases. 3. They have low melting points and boiling points because not much energy is needed to separate the molecules from each other.
4. They are insoluble in water.
5. They do not conduct electricity.
Ionic and Covalent
compounds
Covalent bond
In a covalent bond the electrons are shared between the atoms involved, but the same rule applies, the atoms will try to gain eight electrons in their outer shells (octet rule).
Example 2; Draw a molecule of water, H2O.
From the diagram we can see that the oxygen atom has six electrons on the outer shell. It shares two electrons, one from each hydrogen, and obtains eight electrons on its outer shell. This makes the oxygen atom stable. The hydrogen atoms are also stable because each has two electrons in their first shell, which is all they need.
Example 1; The formation of covalent bonds in a molecule of methane, CH4 .
The Carbon atom has 4 electrons in the outer shell. It will share 1 electron with each of the hydrogen atoms, therefore obtaining 8 electrons in the outer shell, at least part of the time.Hydrogen will have 2 electrons in the outer shell, which is all it needs as the first shell holds only 2 electrons anyway.
Therefore, carbon forms four covalent bonds with the hydrogen atoms.
N
C
After the bond is formed
Na+
Magnesium Cl
-Magnesium ion
N C
Electron transfer Before the bond is formed
Magnesium atom
Oxygen atom Before electrons
transferred
Mg+2
Magnesium ion O
-2
Oxygen ion After electron transfer
Hydrogen atoms
Carbon atom Oxygen
atom
Acids and bases
An acid is a substance which turns litmus solution red.
A base is a substance which turns litmus solution
blue.
Bases which are soluble in water are called alkalis.
An indicator is a substance which, by means of acolour change, shows whether a substance is an acid or a base. The most commonly used indicator is litmus but there are many others.
The strength of an acid or base - The pH scale
If we need to know the strength of an acid or base we use the ‘pH scale’. The pH scale goes from 0 to 14. The scale can be summarised as follows;
← acid → neutral ← base →
Mandatory experiment; How to find the pH of various substances.
To find the pH of a solution simply dip a piece of the universal indicator paper into the solution. Compare the new colour of the paper with the chart and record the pH.
Procedure
1. Place small quantities of various solutions into a number of test tubes. 2. Dip a piece of universal indicator paper into each of the solutions and
note the colour change.
3. Compare the colour to the chart provided with the indicator paper.
Making a salt
When an acid reacts with a base a salt and water are formed. This can be written as a word-equation.
Acid
Base
S
alt
Water
This kind of reaction is called a neutralisation reaction.The simplest acid-base reaction to choose is that between hydrochloric acid (HCl) and sodium hydroxide (NaOH).
The chemical equation for the reaction between these two chemicals is,
HCl
NaOH
NaCl
H
2O
In words this may be written as,
chloride hydroxide acid water sodium sodium ic
hydrochlor
Common laboratory acids Hydrochloric acid (HCl) Sulphuric acid (H2SO4)
Common laboratory bases Sodium hydroxide
(NaOH)
Common everyday acids
Fizzy drinks (carbonic acid)
Orange juice (citric acid) Vinegar (ethanoic acid) Tea (tannic acid) Sour milk /yogurt (lactic
acid)
Common everyday bases Toothpaste
Soap
Window cleaner
Oven cleaner
A fuel is a substance that burns in oxygen to produce heat.
Fossil fuels are fuels formed from the remains of dead animals and plants over millions of years.
Hydrocarbon fuels consist of carbons and hydrogen only. When they burn they produce water and carbon dioxide.
Acid rain contains water with a ph of less than 5.5. this rain contains sulphuric acid(from burning fossil fuels) and nitric acid (from the burning of petrol).
Procedure
Measure 20 cm3 of sodium hydroxide solution into the conical flask, using a pipette.
Add two drops of litmus indicator to the flask.
The litmus will be blue in colour.
Fill the burette with hydrochloric acid.
Allow the acid to run into the base in the conical flask.
As soon as the indicator changes to a red colour, stop the flow of acid from the burette.
The acid has now neutralised all the base.
Record the volume of acid used.
Repeat the procedure without the indicator and stop at the same point.
Take the solution in the conical flask [salty water] and evaporate off the water and you are left with salt.
Reactions of acids
O
H
NaCl
NaOH
HCl
water
salt
base
acid
2
Water
Water is a compound made up of hydrogen and oxygen.
The chemical formula for water is H2O.
Water turns blue cobalt chloride paper pink.
It freezes at 0oC and boils at 100oC.
Water expands when it freezes. This means that ice will be less dense than water and therefore floats in water.
Water is also an excellent solvent as it can dissolve thousands of different substances.
Water cycle
Water evaporates from the sea into the sky
It condenses as it rises and forms clouds.
As the clouds cool, further condensation cause the drops to become too heavy and they fall to earth as rain, snow, hail.
Into rivers and lakes and back out to sea.
Cycle starts again.
Water treatment
1. Screening; A mesh removes large objects from the water. 2. Settling; The water is pumped into large tanks and allowed to sit.
Insoluble solid particles settle to the bottom e.g. sand, stones and grit. 3. Filtration; The water is then filtered through beds of sand. This
removes all the visible dirt and suspended particles. 4. Chlorination ; Chlorine is added to the water to kill bacteria. 5. Fluoridation; Sodium fluoride is added to the water to prevent tooth
decay.
Mandatory experiment; To compare various samples of water for hardness
1. Into four test tubes place a sample of tap water, bottled water, river water and deionised water. 2. Put the same quantity of each sample into the separate
test tubes.
3. Add a drop of soap solution from a dropper into each. 4. Shake all four for an equal time.
5. Allow to sit.
6. Compare the four test tubes.
7. The sample which produced the most permanent suds is the softest water and the sample with the least quantity of suds is the hardest water.
Mandatory experiment; To show that water contains dissolved solids
1. Place a sample of water in an evaporating dish. 2. Place the dish on top of a beaker of boiling water. 3. Eventually, the water in the dish will evaporate
and the dish will be dry but a residue of solid material will be left behind.
Ways of removing hardness
1. Distillation - expensive but removes all hardness. 2. Ion exchange resins – The most effective method of
removing hardness. Water is passed through a container of resin. The positive ions are exchanged for
H+ ions and the negative ions for -OH ions. The H+and
–OH ions combine and form water.
Hard water.
Is water which does not lather easily with soap.
Soft water
Is water whichlathers easily with soap.
Hard water is caused by presence of calcium or magnesium ionsin water.
The calcium ions react with the soap molecules to form a scum which is insoluble in water.
Calcium
ions
Soap
Scum
Calcium ions get into rainwater when acidic rain reacts with insoluble limestone (calcium carbonate) and forms soluble calcium hydrogen carbonate.
Advantages of hard water
1. The calcium ions are good for teeth and bones. 2. Nice taste.
3. The calcium ions are needed for brewing.
Disadvantages
1. It blocks pipes and leaves limescale on kettles and boilers. 2. It wastes soap.
3. It produces scum with soap.
Electrolysis of water
When you pass an electric current through water the water molecules are broken-up and form hydrogen and oxygen gases. The instrument used to do this is the Hoffman voltameter. The breakdown of a compound by an electric current is called electrolysis.
Soft water Hard water
Ion exchange resin
Hydrogen gas Oxygen
A metal is an element which loses electrons easily to become positively charged.
The properties of metals
Good conductors of heat and electricity. Lustrous (shiny)
Solid (except mercury which is a liquid) Malleable – can be hammered into thin
sheets
Ductile – can be drawn into thin wires Very dense – they sink in water (except
alkalis which float)
High melting points and boiling points Susceptible to corrosion
Metal alloys
Metal alloys are formed when metals are melted and mixed together. Alloys are usually harder and more resistant to corrosion than the two metals which make up the alloy.
Bronze is a mixture of copper and tin. It is easily melted and used for pouring into moulds and for large statues.
Brass is a mixture of copper and zinc. It is strong and resistant to corrosion.
Steel is a mixture of iron and carbon. It is much harder and more corrosion-resistant than iron.
Corrosion of metals
Corrosion is the process in which a metal combines with another element (usually oxygen) to form a compound of the metal.e.g. Iron
combines with oxygen to form iron oxide. This is a special kind of corrosion and is referred to as rust.
Prevention of corrosion
1. Painting – The paint layers prevent both air and water (and salt) coming in contact with the metal and causing corrosion.
2. Greasing and oiling – This type of prevention is used on moving parts of engines and machines where painting would be scratched off.
3. Galvanising – Cheap metal is coated with a layer of zinc which does not corrode. Used for ‘galvanised’ buckets, bins and roof-sheeting.
4. Chromium plating – A shiny coating of chromium metal, which does not corrode, is used for protecting metals. This is used when a decorative finish is needed. 5. Electroplating – Metals are covered
with a layer of a precious metal using an electric current.
METALS
Experiment; To compare the reactivity of different metals with water and acid.
Add a small piece of each of calcium, magnesium, zinc and copper metals to 4 test tubes.
Add enough water/ acid to each of the test tubes and observe what happens.
Results for water
Bubbles of hydrogen gas are seen rising from the piece of calcium only.
There is no sign of gas from the magnesium, zinc or copper.
Conclusion; calcium is the most reactive of the four metals with water.
Results for acid
Calcium is producing the most hydrogen gas, magnesium is next, and zinc only a small quantity.
Conclusion; calcium is the most reactive of the four metals with acids, magnesium is the next most reactive, followed by zinc and copper is the least reactive of all.
Mandatory experiment; To react zinc with hydrochloric acid and test for hydrogen gas
Place the zinc into a flask of dilute hydrochloric acid.
Collect the gas as shown.
Test this gas by bringing a lighted taper near the mouth of the test tube.
The gas will burn with a loud ‘pop’.
Properties of plastics Can be easily moulded.
Easy to maintain (don’t rust or rot).
Not expensive
Light weight
Good insulators of heat and electricity.
Biodegradable plastics are those which can be broken down in the environment by micro-organisms.
Plastics are man-made materials made from crude oil.
Examples of plastics; Polythene – for making shopping bags, bins, sandwich wrap etc.
Polystyrene – used for burger boxes, egg boxes, foam packaging.
Polypropylene – hard plastic material in chairs, luggage casing.
Nylon – rope, brushes, string for tennis rackets.
Pvc – drain pipes, guttering,
electrical goods.
Mandatory experiment; to investigate the conditions necessary for rusting
Set up the apparatus as shown across .
The nail in test tube A will rust because it has oxygen and water.
The nail in test tube B will not rust because it has no water (the calcium chloride will absorb the water from the air).
The nail in test tube C will not rust because it has no oxygen (boiled water has no oxygen). The oil layer prevents oxygen from re-dissolving in the water.
The conclusion; iron requires both water
and oxygen to rust.
Hydrogen gas collected
Zinc
