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CHEMISTRY

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steve taylor

on 29 October 2016

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Transcript of CHEMISTRY

CHEMISTRY
PARTICLES
particle theory- explains the property of matter by assuming that all substances are made up of tiny particles.
atom- particles from which substances are made.
molecule- particles made from atoms chemically joined together
solid particles are packed together. liquid particles are free to move, but slowly. gas particles can move wherever they want as fast as they want.
SOLIDS, LIQUIDS AND GASES
if a gas is in one syringe, a liquid in the other and a solid in the other it is harder to push the syringe to a certain point.
the gas syringe is easy to push down as the gas particles are so far apart. the liquid syringe was able to reach half way and the solid syrine was impossible. this shows gases take up the most space and solids take up the least.
DIFFUSION
diffusion- movement of particles from an area of high concentration to low concentration.
BROWNIAN MOTION
robert brown discovered it, by looking through a microscope at some soot and pollen grains.
because these objects were not alive it did not make sense that they were moving.
it was actually the water molecules in the air that were moving them.
MATTER
Matter- a substance that is made up of atoms and molecules, all substances in the universe are made up of matter.
there are three states of matter. solid, liquid and gas.
solid
gas
liquid
evaporation
condensing
sublimation
reverse sublimation
freezing
melting
BOILING POINT AND MELTING POINT
boiling point- this is the temperature where a liquid turns into gas.
melting point- this is the temperature where a solid turns into a liquid.
COMPOUND
an example of a compound is water
its chemical formula being H2O it has more than one element.

compound symbol valency if H added

hydroxide OH 1 water H20
nitrate NO3 1 nitric acid HNO3
sulpate SO4 2 sulphuric acid H2S04
carbonate CO3 2 carbonic acid H2CO3


Compounds always contain a fixed amount of each element ie they have a fixed composition.

FORMULA
formula- is a collection of symbols representing one molecule of an element or compound.
for example copper sulphate its formula is CUSO4.
VALENCY
FORMULAE OF COMPOUNDS
if there are two numbers in a compound you have to use brackets.

metals always come first.

valency has to be small.

name of non metal comes second and change ending to "ide"

compounds containing two elements plus oxygen the name of the second element
changes to "ate"


element 1 element 2 element 3 name of compound

copper Cu2 bromine Br -------------- copper bromide CuBr2
silver Ag sulphur S2 -------------- Silver sulphide Ag2S calcium Ca2 oxygen O2 ------------- calcium oxide CaO
nickel Ni2 sulphur S2 oxygen O2 nickel sulphate NiSo4
magnesium Mg 2 nitrogen N3 oxygen O2
aluminium Al3 Bromine Br oxygen O2
BALANCING EQUATIONS
you must balance every element.

you can't alter the formulae, you can only double, treble, etc.

MAKING HYDROGEN
Hydrogen is an element.
acids
sulphuric acid=H2SO4
hydrochloric acid=HCL
nitric acid=HNO3
Carbonic acid=H2CO3

important reactions
metal+water=metal hydroxide+ hydrogen
e.g. sodium+water= sodium hydroxide+hydrogen
Na

metal +acid= metal salt+ hydrogen
e.g. sodium+sulphuric acid=sodium sulphate+hydrogen

metal+steam= metal oxide+ hydrogen
e.g. potassium+steam(h2o)=potassium oxide+hydrogen

reactivity series
displacement reactions
"a more reactive metal displaces a less reactive metal from its compound"
e.g. zinc chloride +sodium=sodium choride +zinc
copper sulphate+potassium= potassium sulpate+ copper

hydrogen (H2)
not soluble in water
no colour
no odour
heavier than air
hydrogen doesn't support combustion
you can make hydrogen by adding sulphuric acid to a reactive metal
e.g. zinc and sulphuric acid=zinc sulphate+H2


reducing agents-
remove oxygen from a compound


oxidising agents-
add oxygen to a compound

hydrogen + metal oxides =water (H2O)+metal

Definitions symbols valency and formula

atom
-smallest particle of an element that can take part in a chemical change.

molecule
- smallest part of an element that can exist independently. eg O=element O2 =molecule

elements
- contains only one type of atom.

compound
- contains two or more elements chemically joined together. eg H20

symbol
- represents one atom of an element. eg Cl

formula-
collection of symbols representing one molecule of an element or compound eg Mg2 or MgSo4

valency
- a vague of idea can be thought of as the number of chemical bonds an atom can make.



FORMULAE OF COMPOUNDS 2
Formulae of Compounds

COMPOUND SYMBOL
Water H2O
HydroGen chloride HCl
Sulphuric acid H2SO4
Copper (11) oxide CuO
Calcium oxide CaO
Iron (11) chloride FeCl2
Potassium hydroxide KOH
Magnesium sulphate MgSO4
Lead carbonate Pb(CO3)2
Sodium chloride NaCl
Silver nitrate AgNo3
Silver chloride AgCl
Potassium carbonate K2CO3
Sodium oxide Na2O
Potassium sulphate K2SO4
Nitric acid NO3
Copper (11) carbonate CuCO3
Sodium hydroxide NaOH
Sodium carbonate Na2CO3
Iron (111) oxide Fe2O3
Calcium sulphate CaSO4
Calcium carbonate CaCO3
Sodium nitrate NaNO3
Potassium oxide K2O
Aluminium oxide Al2O3

Formulae
ELEMENT Fluorine Nitrogen Oxygen Bromine Carbon Chlorine Silicon Sulphur Iodine
Hydrogen HF H3N H2O HBr H4C HCl H4Si H2S HI
Calcium CaF2 C3N2 CaO CBr2 X CaCl2 X CaS CaI2
Sodium NaF Na3N Na2O NaBr X NaCl X Na2S NaI
Potassium KF K3N K2O KBr X KCl X K2S KI
Iron (11) FeF2 Fe3N2 FeO X X FeCl2 X FeS FeI2
Iron (111) FeF3 FeN Fe2O3 X X FeCl3 X Fe2S3 FeI3
Aluminium AlF3 AlN Al2O3 AlBr3 X AlCl3 X Al2S3 AlI3
Copper CuF2 Cu3N2 CuO CuBr2 X CuCl2 X CuS CuI2
Magnesium MgF2 Mg3N2 MgO MgBr2 X MgCl2 X MgS MgI2
Zinc ZnF2 Zn3N2 ZnO ZnBr2 X ZnCl2 X ZnS ZnI2

Carbon dioxide CO2

Only carbonates give of carbon dioxide.

Carbonate CO3

When carbonate is added, the acid efferveces and when the carbonate is burnt it will produce CO2.

metal carbonate->metal oxide+ carbon dioxide

Carbon dioxide is denser than air.


Carbon Dioxide
Testing for CO2

With a pipette squeeze the air and squeeze again in a test tube containing limewater. If the water turns white or cloudy this shows that CO2 is within. A method to test is CO2 is inside a solid is to place the solid inside an acid and take a sample with the pipette and use the same process. a method to test for CO2 when heating is to place the solid in a test tube and heat, after a while take a ample with a pipette and use the same process with the limewater again.
Limestone=calcium carbonate=CaCO3
Chalk=Calcium carbonate=CaCO3
Marble=calcium carbonate=CaCO3
Bicarbonate of soda= sodium hydrogen carbonate=NaHCO3
Washing soda=sodium carbonate= Na2CO3
Gypsum=calcium sulphate=CaSO4
Epsom salts=Magnesium sulphate=MgSO4
Salt=sodium chloride=NaCl
Carbon dioxide as Product of Breathing

Two conical flasks were set up with 2 tubes sticking out of both. One flask with a person breathing into the other flask just air. The blowing flask turned cloudy first.
RULE: When carbonate is added the acid efferveces and if it is burnt it will produce CO2.
Products of Burning Fuels

When a fuel is burnt, it gives off CO2 [limewater white/cloudy] and H2O [anhydrous copper sulphate blue], they also react with O. The main purpose of burning fuels is to create energy.

Properties of CO2

3 candles were placed in a plastic box, CO2 was put in and the experiment showed the lower the candle the quicker it went out.

4 glass jars were set up, two on top of the others. 2 jars contained air the other 2 CO2. one CO2 jar was placed on top of an air jar the other underneath the air jar. the bung between the jars was taken off and left for 20 seconds. on the jar with the air on top the lighted splint went out immediately, on the other it took a while because not all of the CO2 had got to the bottom of the jar.
Rocks- are a mixture of different minerals
Minerals- are elements or compounds found within the Earth
Sedimentary-small pieces stuck together by salt from rocks above. e.g. sandstone, limestone, chalk

Igneous-liquid rock magma/lava, e.g.granite, basalt




Metamorphic- rocks acted on by heat and pressure over time e.g. marble, slate
Rocks
Angular- angles and sharp corners

Cleavage-planes of weakness

Course-grained-large crystals

Equigranular-even grained

Foliation-parallel alignment of sides

Friable-crumbles easily

Homogenous-all same kind

Lineation-parallel crystals

Phenocryst-large crystal in rock

Vesicle- small hole in volcanic rock
Lava cools quickly to form igneous rock with small crystals. Magma trapped cools slowly to form igneous rock and large crystals
Weathering
Temperature changes can cause physical weathering. The rock expands during the day, when its hot and contracts at night when it's cold. Plant roots can cause biological weathering. The plant roots grow into small cracks in the rocks. And push the sides of the cracks apart when they grow bigger. Freeze thaw action can cause physical weathering. Water in the rock expands when it freezes and makes the cracks bigger. Rain can cause chemical weathering. The acid in the rain dissolves part of the rock. The process is speeded up if the rain contains a lot of acid. Rain like this is called acid rain and can be caused by burning fossil fuels.
Solids, liquids and gases
There are 3 types of state: solid, liquid and gas that matter can exist as.
solid ------> liquid ------> gas

melting evaporating

solid <------liquid <--------gas


freezing condensing

solid ------->gas
sublimation

solid <--------gas
reverse-sublimation
Diffusion- where particles of a substance spread out (diffuse) through another substance.
Diffusion happens quicker when the particles are smaller.
Atoms
Atomic Structure
Every substance is made up of atoms
Each of these atoms is made up of 3 sub-atoms (electrons, protons and neutrons)
Position
Mass
Charge
Electron
Proton
Neutron
Shells
Nucleus
Nucleus
1
1
1/1836
-1
+1
0
.




Every element has a symbol
On the periodic table each symbol has 2 numbers. The larger of the 2 numbers is the mass number and represents the number of protons and neutrons in one atom.

The smaller number is the atomic number and represents the number of protons in an atom.
Electron arrangements

In shell 1 there are 2 electrons in all the others there are 8 (maximum)
Isotopes
Atoms of the same element (same protons) but have different numbers of neutrons (hence different mass numbers)
Moles
Empirical formulae is the simplest formula of a compound.
Percentage composition is found by all the masses in the compound being added then divided to find the percentage of each separate substance.
Chemical formula
Reacting masses
To work out how much of a substance will be obtained by reacting it with another compound you have to :
find out the mass of the whole compound(usually given to you)
find the mass of 1 mole.
When you have this information you divide the mass by the mass of 1 mole. Then you work out the mass of 1 mole of the other compound and multiply it by the number of moles to get the mass.
Finally, you multiply the mass of the product you found and multiply it by the mass other the product you were given and divide that by the mass of 1 mole to find out how much can be obtained.
Percentage yield
To work out the percentage yield of a reaction you compare the mass of the product you made with what you were expecting to make.
Compounds are substances in which atoms of two or more elements are chemically combined.
Bonding and Structure
Bonding involves either transferring or sharing electrons. Atoms that lose electrons are positively charged. Atoms that gain them are negatively charged.
When atoms form bonds by transferring electrons they form ions.
Ions have the electron arrangement of a noble gas.
Metals form positive ions. Non metals negative ions.
Ionic compounds are held together by electrostatic forces.
An ionic structure is a giant structure of ions.
When atoms share pairs of electrons they form covalent bonds. They are strong.
When melted or dissolved in water ionic compounds conduct electricity because the ions are free to move and carry the current.
Ionic Bonding
Chemical combination
When forming chemical bonds it is only the number and arrangement of electrons that matter.
Covalent Bonding
Covalent bonding is the bonding between non metals only.
very strong electrostatic forces of attraction are between ionically bound compounds.
Ionic compounds have:
high melting points and boiling points
Solid at room temperature
Soluble in water
Will conduct when molten/dissolved in water.
The bonds between atoms within molecules are strong but there are only weak forces between the molecules.
Covalent compounds have:
low melting points and boiling points
Gases at room temperature
Not soluble in water
Do not conduct electricity.
When heated covalent
substances
weak
inter
molecular forces are broken.This doesn't take much energy so they have low boiling/melting points. The intermolecular forces are what hold the compounds together.These weak forces are also called Van Der Wall forces.
Covalent
bonds
are strong they are joined by
intra
molecular forces. Bonds hold the atoms within the compound together.
Ions
Four types of structure
There are four key types of structure.
Giant Ionic Lattice
High melting/boiling point
Ionically bonded
Conducts as a liquid
Have electrostatic forces
Giant Metallic Lattice
High melting/boiling point
Metallically bonded
Conducts as a solid
Have electrostatic forces
Giant Covalent Substance
High melting/boiling point
Covalently bonded
Never conducts
Have covalent forces
Molecular Covalent Substance
Low melting/boiling point
Covalently bonded
Never conducts
Have electrostatic forces
Ionic bonding takes place between a metal and a non metal.
Single, Double and Triple bonds can be formed by having one pair, two pairs or three pairs of electrons between them.
All metals conduct electricity because outer electrons can move around the metallic structure. They are called delocalised electrons. The more delocalised electrons the metal has the better conductor it is.

Na
23
11
Mass number
Atomic number
Na
23
11
Mass number
Atomic number
All atoms are neutral therefore there is no overall charge so the number of protons must be equal to the number of electrons.
Elements
A substance that is made up of atoms with the same atomic number is called an
element.


Elements can't be broken down chemically. Atoms of different elements have different properties.

About 100 different elements have been discovered. The elements can be represented by
symbols.


Approx 80 % of elements are
metals
. Metals are found on the left hand side of the periodic table.

The
non-metal
elements on the right hand side of the periodic table. Elements with
intermediate properties
are found in group 4.
Isotopes
Cl
Cl
37
17
35
17
Cl
35.5
17
17 protons
17 electrons
18 neutrons
17 protons
17 electrons
20 neutrons
25% of chlorine atoms
have an atomic mass of 37
75% of chlorine atoms
have an atomic mass of 35
This gives an average
atomic mass of 35.5
Definitions symbols valency and formula

atom
-smallest particle of an element that can take part in a chemical change.

molecule
- smallest part of an element that can exist independently. eg O=element O2 =molecule

elements
- contains only one type of atom.

compound
- contains two or more elements chemically joined together. eg H20

symbol
- represents one atom of an element. eg Cl

formula-
collection of symbols representing one molecule of an element or compound eg Mg2 or MgSo4

valency
- a vague of idea of the number of chemical bonds an atom can make.



An
atom
has a very small, central
nucleus
that is surrounded by shells of
electrons
The nucleus is found at the centre of the atom. It contains
protons
and
neutrons
.
Compounds are made when atoms of two or more elements are chemically combined.
Ionic bonding
involves the transfer of electrons in the outermost shell of
atoms
.

This forms ions with opposite charges, which the attract each other.
Ions are atoms or groups of atoms with a charge.
Ionic bonding involves the transfer of electrons from one atom to another.
There is an electrostatic attraction between the nuclei of the atoms and the bonding electrons.
These diagrams show the transfer of electrons and how the atoms have become positively and negatively charged to create ions.
These diagrams show how the atoms are sharing their electrons. Ions are not formed because covalent structures are formed by sharing electrons.
Diamond is an example of this. It is very hard, has a high melting.
Graphite is the same but its surfaces are able to slip and slide. That is why it is used as pencil lead because when it travels across paper it leaves a black mark.
MATTER
Matter- a substance that is made up of atoms and molecules, all substances in the universe are made up of matter.
there are three states of matter. solid, liquid and gas.
solid
gas
liquid
evaporation
condensing
sublimation
reverse sublimation
freezing
melting
n = number of moles
m= mass of substance
rm= relative molecular mass

e.g. there are 24g of carbon how many moles are there?

24 / 12 = 2 moles
You work out moles by the mass of the element divided by its mass number.
Relative formula mass = all masses in the compound added together.
Why is relative atomic mass used?
Relative Atomic Mass (RAM/Ar)
is used to compare the masses of different atoms.

The RAM of an element is the average mass of its isotopes compared with an atom of Carbon 12.
He
4
2
Mass number
Atomic number (proton number)
Relative Formula Mass
The
Relative Formula Mass
(RFM/Mr) of a substance is worked out by adding together the
Relative Atomic Mass
(RAM) of all the atoms in the ratio indicated by the formula.
N
2
(2 X 14 ) = 28
CO
2
12 + (2 X 16 ) = 44
H O
2
(2 X 1 ) + 16 = 18
The
relative formula mass
of nitrogen is 28
The
relative formula mass
of Carbon Dioxide is 44
The
relative

formula mass
of water is 18
The
molar mass
of a substance is its relative formula mass in grams. The units for molar mass are g/mol.
Moles
The Relative Formula Mass of a substance in grams is known as 1 mole of the substance. This is also called the molar mass.

1 mole of Carbon Dioxide is 44g and 1 mole of Water is 18g. The number of moles of a substance present can be calculated using this formula:

mass of sample
Number of moles = ----------------------------
RFM of the substance
Molar mass
The
molar mass
is the
mass of 1 mole of a substance in grams
.


mass of sample
The
number of moles
in a sample of substance= -----------------------

molar mass
e.g. How many moles are present in 60g of calcium carbonate?
Ca C O
40 12 48 = 100
3
60
---- = 0.6 MOLES
100
Avogadro's Number
One mole of any substance contains 6 X 10 particles. This is known as Avogadro's number. It can be used to work out how many moles are present.
23
number of particles in the sample
Number of moles = --------------------------------------------
number of particles in one mole
e.g. a sample contains 4.5 X 10 particles How many moles of a substance are present? 4.5 X 10
------------- = 0.75 moles
6 X 10
23
23
23
Finding Empirical Formula
The empirical formula of a compound is the simplest whole number ratio of atoms it contains.
e.g. Find the empirical formula of magnesium oxide formed when 12g of magnesium reacts with 8g of oxygen. (Deal with the magnesium and oxygen separately.)
State the no. of g that combine
Mg
O
Change the g to moles
Ratio in which atoms combine
Ratio of simplest form
12
12
----
24
0.5
1
1
0.5
8
----
16
8
One mole of any gas occupies a volume of 24dm at room temperature and pressure. This is known as the molar volume of a gas.
Volume in dm = number of moles X 24
e.g. What is the volume of 1.5 moles of carbon dioxide?

Volume in dm = number of moles X 24
= 1.5 X 24
= 36 dm
3
3
Concentration
The concentration of a solution is a measure of how much solute is dissolved in 1 dm of solution.

It is sometimes used to describe how many moles are dissolved in 1 dm of a solution and has the units mol dm .
3
3
-3
Concentration = moles
-----------------
volume in dm
3
e.g. If 2 moles of sodium hydroxide pellets are added to distilled water and the total volume of the solution is 2 dm , what is the concentration of the solution?
3
Concentration = 2 moles
-------------
2 dm
3
= 1 mol dm
-3
The Periodic Table
Group 1 - The Alkali Metals
Li-Lithium
Na-Sodium
K-Potassium
Rb-Rubidium
Cs-Caesium
Fr-Francium
increase of reactivity
increase of 1 full shell of outer electrons
When the proton and electron are close together there's a strong electrostatic force between them.
The group 1 elements are also known as alkali metals. They are very reactive, producing alkaline solutions when reacted with water. Lithium, at the top of the group, is less reactive than caesium, near the bottom of the group. These elements always form ionic compounds.
The History of the Periodic Table
John Dalton
John Newlands
Dmitri Mendeleev
Arranged the elements in order of their mass
Published a book called 'A New System of Chemical Philosophy', which contained a table of elements
Produced a table of octaves
Assumed all elements had been found
Even put 2 elements in the same place her was so certain it was correct.
Arranged 50 elements by atomic mass
Arranged them so there was a pattern
Left gaps in the table for new elements
The Transition Metals
Nearly all the transition metals have high melting points and densities
The transition metals are strong and hard.
They are good conductor of electricity and heat
The transition metals do not react vigorously with oxygen or water.

the transition metals are a block of elements that ie between groups 2 and 3 in the periodic table. These elements are good conductors. They are also less reactive than alkali metals and often form coloured compounds.
The Halogens
The halogens exist as diatomic molecules
The halogens all form ions with a single negative charge
The halogens form covalent compounds by sharing electrons with other non-metals
The reactivity of the halogens decreases going down the group.
Group 7 elements are also called the halogens. Fluorine, at the top of the group, is the most reactive, while iodine is much less reactive. All of these elements exist as molecules made up of two atoms. They react with other non-metals to form covalent compounds and with metals to form ionic compounds.
Noble gases
All noble gases have stable electron configurations (i.e. full outer shell). Therefore they are not reactive.
They are monotomic
He
Ne
Ar
Kr
Xe
Rn
F
Cl
Br
I
At
Acids, Bases and salts
Strong acid - a strong acid is an acid that is 100% ionised in water. e.g. H2SO4,HCl,HNO3
Strong alkali- a strong alkali is an alkali that is 100% ionised in water. NaOH, KOH
Weak acid- A weak acid is only partly ionised in water.
Weak alkali - A weak alkali is only partly ionised in water.
Moles in solution
A 1 Molar solution contains : 1 mole of solid dissolved in enough water to make the volume 1dm (1000cm )
A 2 Molar solution contains: 2 moles of solid dissolved in enough water to make the volume 1dm (1000cm )

Molarity is a measure of concentration of solutions. The more moles the more concentrated the solution.

concentration = moles / volume
Titration calculation

C x V
n= -----------
1000
number of moles = concentration x volume / 1000.
N x 1000
c=---------------
V
concentration = number of moles x 1000 / volume
Neutralisation
A neutralisation reaction occurs when an acid reacts with an alkali to form a salt and water.
Acid's give H ions
Alkali's give OH ions
+
-
N x 1000
v = --------------
C
volume = number of moles x 1000/ concentration
Alkanes
Carbon
Carbon atoms have the ability to form four bond with other atoms.
These atoms can be made into a large number of compounds.
These compounds are the basis of life.
Organic compunds contain covalent bonds

Alkanes are made up of hydrocarbons. They only contain hydrogen and carbon atoms. Most compounds in crude oil contain hydrocarbons.

Alkanes are saturated hydrocarbons, they only contain single carbon bonds, therefore the max number of hydrogen atoms.

All alkanes have the same formula (homlogus series). Cn+H2n + 2
Methane 1 ch4
Ethane 2 c2h6
Propane 3 c3h8
Butane 4 c4h10
Pentane 5 c5h12
Hexane 6 c6h14
The longer the chain length the higher the boiling point.
Intermolecular forces hold the compounds together and are strong
Crude oil
Boiling point = condensing point
Higher boiling points condense first
Residue -> Diesel -> Kerosene -> Naptha -> Petrol -> Refinery gas
Isomers
Isomers have the same molecular formula and different structural formulae.
They have the same number and kind of atoms but are arranged in different ways.
Cracking
Cracking allows large hydrocarbon molecules to be broken down into smaller, more useful hydrogen molcules. Fractions containing large hydrocarbon molecules are vapourised and passed over a hot catyalst. This breaks chemical bonds in the compounds and forms smaller hydrocarbon molecules.
Hydrocarbons
volatility = tendancy to turn into a gas
viscousity = thickness
Incomplete combustion is a reaction without enough oxygen.

Carcinagenic compounds can cause cancer.
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