Chemistry: 1. States of MatterPlease remember to photocopy 4 pages onto one sheet by going A3→A4 and using back to back on the photocopier

SyllabusOC1 Name three states of matter and know their characteristics

Student NotesCharacteristics of Solids, Liquids and Gases

Explanation

Atoms are really, really small

These particles are so small that two million of them would fit into the full stop at the end of this sentence!

It’s not surprising that it took thousands of years before people believed that atoms exist. In fact many scientists, even Albert Einstein, were doubtful that atoms existed at all!We can now see atoms using special hi-tech microscopes.

Now however we know that not only do these ‘atoms’ exist, but in fact they are always moving (jiggling), no matter how hot or cold the object is, and it is this movement that determines whether the object is a solid, a liquid or a gas.

Chemistry: 2. Solutions

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Matter can exist in three states – solid, liquid and gas

1. Every ‘thing’ is made up of very small particles (which we call ‘atoms’).2. Atoms jiggle

Solids Liquids Gases

Definite shape No definite shape No definite shape

Definite volume Definite volume No definite volume

Hard to compress Hard to compress Easy to compress

Do not flow Flow easily Diffuse to fill all available space

Change of State DescriptionSolid – Liquid Melting

Liquid – Solid Freezing

Liquid – Gas Boiling

Gas – Liquid Condensing

Please remember to photocopy 4 pages onto one sheet by going A3→A4 and using back to back on the photocopier

SyllabusOC15 Investigate the solubility of a variety of substances in water and the effect of temperature on

solubility

OC16 Examine the difference between a dilute, concentrated and saturated solution

OC17 Grow crystals using alum or copper sulfate

Student Notes

The solid is referred to as the solute.The liquid is referred to as the solvent.

A solution can be made more concentrated by adding more of the solute or evaporating off some solvent

Experiment: To investigate the solubility of a variety of substances in water and the effect of temperature on solubilityExample; table saltDetermine the maximum mass, in grams, of salt that will dissolve in 100 g of water at various temperatures.Plot a graph of the results (see exam questions)

CrystalsSome solids are always found in the form of a crystal.Crystalline solids have definite shapes because the atoms in the crystal are in a regular pattern.Examples include sugar and salt diamonds and ice.

Salt is composed of two different types of atom, sodium (symbol Na) and chlorine (symbol Cl), arranged in an orderly pattern as shown.

Other solids are said to be non-crystalline.Example: flour

Mandatory Experiment: To grow crystals using copper sulphateProcedure:Keep adding copper sulphate powder to hot water until no more will dissolve.Allow to cool slowly.Result:Crystals begin to grow

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A solution is formed when a solid dissolves in a liquid

A dilute solution is one where there is a lot of solvent and only a little solute

A concentrated solution is one where there is a lot of solute and only a little solvent

A saturated solution is one where no more solute will dissolve in the solvent

Chemistry: 3. Separating MixturesPlease remember to photocopy 4 pages onto one sheet by going A3→A4 and using back to back on the photocopier

SyllabusOC2 Separate mixtures using a variety of techniques: filtration, evaporation, distillation and paper

chromatography

OC32 Carry out a simple distillation, and obtain a sample of water from sea-water

Student Notes

If two substances are chemically combined then it is very difficult to separate them but if they are just mingled together or dissolved then it is usually straightforward.

An insoluble solid is a solid which doesn’t dissolve in a liquid, e.g. a soil in water

Equipment:A solution of soil and water, filter paper, filter funnel, conical flask and beaker.Procedure:Carefully pour the solution into the conical flask – the water will flow through, leaving just the soil behind.

A soluble solid is a solid which dissolves in a liquid, e.g. a sugar in water

The problem is that you lose the liquid. Procedure: Simply heat the mixture (e .g. water and salt) – the water will evaporate, leaving just the salt behind.

Chemistry: 12. Elements, Compounds and Mixtures3

Evaporation is used to separate a soluble solid and a liquid

Filtration is a way of separating an insoluble solid from a liquid

A mixture is made up of two or more substances mingled together but not chemically combined

Please remember to photocopy 4 pages onto one sheet by going A3→A4 and using back to back on the photocopier

SyllabusOC3 Understand what an element is and recall that all known elements are listed in the Periodic Table;

understand what a compound is and what a mixture is; recall that when elements combine to form compounds they may lose their individual properties

OC4 Examine a variety of substances and classify these as elements or compounds (using the Periodic Table as a reference)

OC12 Compare the properties of the simple compounds H2O, CO2, MgO and FeS to those of the constituent elements

OC13 Compare mixtures and compounds made from the same constituents, and understand that an alloy is a mixture

Student NotesWe saw in a previous chapter (States of Matter) that everything is made of atoms.We also saw that there are many different types of atom (over 100 in fact), and some substances are made from just one type of atom, while other substances are made from combinations of different types of atom.

ElementsIf a substance is composed of just one type of atom then that substance is known as an element.Copper wire is made up of only copper atoms; a gold ring is composed of only gold atoms. We say that copper and gold are elementsWe have already seen that the different types of elements are arranged in terms of their atomic number (the number of protons in the nucleus) in a table called the Periodic Table of elements.

Compounds

An example of a compound is table-salt. It is a compound because it is made up of two different types of atom – in this case sodium and chlorine. The chemical name for table-salt is NaCl.

The interesting thing is that both sodium and chlorine can be fatal if ingested (swallowed) on their own, but when the two go together to form table-salt the result is perfectly safe (once you don’t eat too much!).We can summarise this as follows:

Other examples of compounds and their constituent elements

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Elements are substances which are made up of only one type of atom

A compound is formed when two or more atoms of different elements combine together chemically

When elements combine to form compounds they often lose their individual properties

Compound Symbol State of matter

(at room temp)

Elements in the compound(and state at room temp)

Water H2O liquid Hydrogen (gas)oxygen (gas)

Carbon dioxide CO2 gas Carbon (solid)oxygen (gas)

Magnesium oxide MgO solid Magnesium (solid)oxygen (gas)

Iron sulphide FeS solid Iron (solid)Sulphur (solid)

MoleculesSome atoms form a very strong attachment (‘bond’) to another atom or atoms and as a result they always go around in groups of two or more atoms. We call these groups of atoms ‘molecules’.It is very hard to break these ‘bonds’ and we say that in this case the atoms are ‘chemically combined’. We will look at this bonding in detail in another chapter.

Also

Basically a molecule is like a very small group of atoms that go around together (they are still too small to see).Examples:For the element oxygen the atoms go around in pairs. These are then called oxygen molecules and that is why oxygen is often represented as O2.

For the compound water the atoms go around in ‘gangs’ consisting of two hydrogen atoms and one oxygen atom. These ‘gangs’ are called water molecules and that is why water is often represented as H2O.

My head hurts; what’s the difference between a compound and a molecule?All compounds are molecules, but not all molecules are compounds (e.g. H2 is a molecule because it is composed of two atoms chemically combined, but because they are both the same element (hydrogen) the molecule is not a compound).O2 is a molecule but it is not a compound for the same reason.H2O is both a molecule (because it is composed of two atoms) and it is also a molecule (because there are two different types of element involved; hydrogen and oxygen).

Remember when we said that atoms are so small that you can’t see them? Well molecules are made up of small groups of atoms so you won’t be able to see them either.

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A molecule is made up of two or more atoms chemically combined

A molecule is the smallest part of an element or compound that can exist on its own

Mixtures

If a substance is made up of different components but they are just mingled together rather than combined at an atomic level then we call this a mixture.

Mixtures can be (fairly) easily separated, whereas compounds cannot be easily separated.

If

you pour sulphur power over iron filings and mix them together you get a mixture, and to separate them simply use a magnet which will attract the iron filings and leave the sulphur powder behind.

However if you heated the mixture to a very high temperature their chemical compositions will change and the two elements will ‘bond’ together chemically to become a new substance called iron sulphide. This cannot now be separated and the result is called a compound.

Summary

Another way of thinking about a compound is that it is a mixture of elements in a fixed ratio.

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A mixture contains two or more different substances mingled together but not chemically combined

A mixture is a combination of elements in an unfixed ratio

Distillation

Two miscible liquids are liquids which mix together, e.g. alcohol and water.

A: Thermometer B: Water out to sink C: Condenser D: Cold water in E: Tripod stand F: Bunsen burner

To obtain a sample of water from sea-water using simple distillationProcedure:1. Set up as shown above.2. Part C is called a condenser; it has an outer tube which carries cold water which causes the water vapour

passing through the inner tube to condense back into a liquid. 3. Cold water goes in through D and out through B.4. The round-bottom flask above the Bunsen burner contains sea-water.Result:The water evaporates from the round-bottom flask, travels through the condenser where it condenses and flows into the beaker as pure water.

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Distillation can be used to separate two miscible liquids with different boiling points (and you get to keep both)

Distillation can be used to separate a soluble solid and a liquid (and you get to keep both)

Chromatography

Procedure1. Put an ink spot just above the water

line as shown.2. Water rises up through the chromatography paper and takes the various colours which were in the ink

spot to different heights.

Chemistry: 8. The Atom

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Chromatography is used to separate a mixture of dies in an ink

Please remember to photocopy 4 pages onto one sheet by going A3→A4 and using back to back on the photocopier

SyllabusOC39 Describe the structure of the atom, state the location, relative charge, and atomic mass of the sub-

atomic particles, and define atomic number and isotope

OC40 Draw the Bohr structure of the first 20 elements

Never trust an atom. They make up everything.Student Notes

In other words, an atom of iron is the smallest piece of iron that shows all of the properties of copper.

Structure of the atomThe atom has a solid central section called the nucleus with very small particles in orbit around it.

The tiny particles that make up the atom are called “sub-atomic particles”.

The protons and neutrons are located in the centre of the atom – called the nucleus.

The electrons revolve around the nucleus of the atom in fixed paths called orbits (shells) to form an electron cloud.

In general atoms are electrically neutral. Therefore the number of protons must equal the number of electrons.

In some atoms the number of protons is also equal to the number of neutrons.But not always - see isotopes below

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An atom is the smallest particle of an element which still retains the properties of that element

There are three different sub-atomic particles: protons, neutrons and electrons

Particle Location Mass ChargeProton Inside the nucleus 1 Unit +1

Neutron Inside the nucleus 1 Unit 0Electron Outside the

nucleus 2000 times

smaller than the mass of a proton

-1

Atomic number

Mass number

ExampleThe atomic number of fluorine is 9 and its mass number is 19.How many (i) protons, (ii) electrons and (iii) neutrons does a neutral fluorine atom have?(i) 9 protons, (ii) 9 electrons (same number as the number of protons), (iii) 10 neutrons (19 – 9)

IsotopesScientists used to think that all atoms of a given element were identical, but then they discovered some elements have two or even three different types of atom. They will all have the same number of protons (e.g. all sodium atoms have 11 protons, all atoms of carbon have 6 protons), but they could have a different number of neutrons.e.g. some atoms of carbon have 6 neutrons, while other atoms of carbon have 8 neutrons. We say these atoms are isotopes of each other.

So carbon-12 has 6 protons and 6 neutrons, but carbon-14 has 6 protons and 8 neutrons.We say that carbon-12 and carbon-14 are isotopes.

Remember If an atom has just one proton in it then that atom must be hydrogen.

If an atom has two protons in it then that atom is called helium etc. The number or protons that an atom contains is called its atomic number – it’s like the atom’s identity

card. Many atoms are ‘neutral’; this means that they contain the same number of positive charges (protons) as

negative charges (electrons).

These are the first 10 elements arranged in order of increasing atomic number:Atomic number

1 2 3 4 5 6 7 8 9 10

Element

Hydrogen Helium Lithium Beryllium

Boron Carbon Nitrogen

Oxygen Fluorine Neon

Symbol H He Li Be B C N O F Ne

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The number of protons in an atom is called the Atomic number

The number of protons plus neutrons in an atom is called the Mass number

Isotopes are atoms which have the same atomic number but different mass number

This means that the number of neutrons = Mass number – Atomic number

Drawing the atoms: A Bohr diagram

This way of understanding the atom was proposed by the Danish scientist Neils Bohr (pronounced “bore”) over 100 years ago, and so these diagrams are known as Bohr diagrams.

While all the protons and neutrons are packed tightly together in the central nucleus, the electrons are arranged in a very specific pattern, according to a set of rules.1. The electrons can orbit (go around) the nucleus as if they are on rings or shells around the nucleus2. Only two electrons can be in the first orbital (shell).3. Up to 8 electrons can be in all the other shells.4. The inner shells must get filled up before electrons appear in an outer shell.

Example: Argon

Argon has an atomic number of 18. This means that it has 18 protons and also 18 electrons. So 2 electrons go in the first shell (represented by black dots).8 electrons go in the next shell.8 electrons go in the outside shell.

We call the arrangement of electrons the electronic configuration.e.g. the electronic configuration of argon is 2,8,8

Calcium has an atomic number of 20, so the electronic configuration of calcium is 2,8,8,2

The next 10 elements:Atomic number

11 12 13 14 15 16 17 18 19 20

Element Sodium Magnesium Aluminium Silicon

Phosphorus Sulphur

Chlorine Argon

Potassium Calcium

Symbol Na Mg Al Si P S Cl Ar K Ca

1. Can you draw the Bohr diagram for the first 20 elements?2. It turns out that there are over 100 different types of element and for years scientists were puzzling over

a way to group different types of atoms together based on some features that they might have in common. Can you think of way of grouping some of the different elements together based on the diagrams you have drawn? (for the answer to this mystery see the chapter entitled The Periodic Table).

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Chemistry: 9. The Periodic Table Please remember to photocopy 4 pages onto one sheet by going A3→A4 and using back to back on the photocopier

SyllabusOC48 Understand that alkali metals are in Group I of the Periodic Table

OC50 Understand that Group II elements are the alkaline earth metals

OC4 Examine a variety of substances and classify these as metals or non-metals

OC5 List the physical properties (state and colour only) of two examples of metallic and two examples of non-metallic elements

OC8 Recall the symbols of the metallic elements Cu, Zn, Al, Fe, Ag, and Au

OC9 Recall the symbols of the non-metallic elements C, O, S, H and N

Student NotesThe Periodic Table

Remember from the last chapter on The Atom that the first10 elements, arranged in order of increasing atomic number (the number of protons in the atom), are as follows:Atomic number

1 2 3 4 5 6 7 8 9 10

Element Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine NeonSymbol H He Li Be B C N O F Ne

The next 10 elements:Atomic number

11 12 13 14 15 16 17 18 19 20

Element Sodium Magnesium Aluminium Silicon Phosphorus Sulphur Chlorine Argon Potassium CalciumSymbol Na Mg Al Si P S Cl Ar K Ca

A mystery solved!The list above is of the first 20 elements – but there are over 100 different types of element and if we arranged them all just in order of increasing atomic number we would end up with one very long row. There must be a better way!

Over 100 years ago, scientists noticed that some of the elements were similar to each other, for example some groups of elements were very reactive while others were very un-reactive; some were solid at room temperature while others were always a gas at room temperature.

Could they use this to help them re-arrange the elements to devise a table that would help them see at a glance which elements go together?

There was one other piece of information which was going to prove vital to solving the puzzle.In the last chapter (The Atom) you were asked to draw all 20 elements and I asked you if you noticed any way to group some of the different elements together?

Well there is, and it is as follows:

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Step One. Group all the atoms which have just one electron in their outer shell together in one column. Group all the atoms which have two electrons in their outer shell together in another column. Do this for all the atoms. We’ll cause these columns ‘Groups’.

Step Two: Keep all the atoms which have just one shell together in one row. Keep all the elements which have two shells together in a second row. Do this for all the atoms. We call these rows ‘Rows’ (‘cause scientists have wonderful imaginations).

What they came up with is now called The Periodic Table of elements.

All the atoms in the first column have one electron in their outer shell; this group is called Group 1.All atoms in the second column have two electrons in their outer shell; this group is called Group 2.All atoms in the last column have a full outer shell; this group is called Group 8 or Group 0.

All the elements in the first row have just one shell.All the elements in the second row have two shells.All the elements in the third row have three shells.

The metals in Group One are given a specific name; they are known as the alkali metals.

The metals in Group Two are also given a specific name; they are known as the alkaline earth metals.

We will look more closely at these groups in a later chapter (entitled The alkali and alkaline earth metals).

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The Periodic Table is an arrangement of elements in order of increasing atomic number

Each column is known as a group and has similar properties

Metals and non-metalsAnother use of the periodic table is to allow us to group metals and non-metals together.

The metals are on the left-hand side of the table and the non-metals are on the right-hand side.Some elements have characteristics of both metals and non-metals and these are known as metalloids.

Properties of metals

1. They conduct electricity2. They conduct heat

Demonstration: Metals conduct electricity1. Put the metal between the points X and Y in the circuit.2. Note that the bulb lights when the switch is turned on.

Demonstration: Metals conduct heat1. Arrange strips of various metals as shown, with a heat source in the centre and solid

wax at the ends. 2. Note the wax melts (and the matches fall) after a short time showing that the heat

was conducted along the metal.

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Non-metallic elementsNon-metallic elements tend to be poor heat and electrical conductors.They are found on the right hand side of the periodic table and tend to be gases at room temperature

Examples of non-metallic elements1. Chlorine (Cl) is a yellow gas2. Oxygen (O) is a colourless gas3. Sulphur (S) is a yellow powder

Experiment: Examine a variety of substances and classify these as metals or non-metalsMethod:Check to see whether the substances conduct electricity and heat as shown above.

Symbols for some metallic and non-metallic elements

Metals Non-metalsMetal Symbol Non-metal SymbolCopper Cu Carbon C

Zinc Zn Oxygen OAluminium Al Sulphur S

Iron Fe Hydrogen HSilver Ag Nitrogen NGold Au

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