Tuesday 29 November 2011
Tuesday 22 November 2011
Electolysis
is the breakdown of a substance by electricity.
Electrolytes are compounds which dont conduct electricity when solid but do when melted or dissolved in water.
• Sulphuric Acid- Electrolyte
• Sodium Chloride- Electrolyte
• Ethanol- not Electrolyte
• Distilled Water- not Electrolyte
• Copper Chloride- Electrolyte
• Glucose Solution- not Electrolyte
• Sucrose Solution- not Electrolyte
Electrolytes are compounds which dont conduct electricity when solid but do when melted or dissolved in water.
• Sulphuric Acid- Electrolyte
• Sodium Chloride- Electrolyte
• Ethanol- not Electrolyte
• Distilled Water- not Electrolyte
• Copper Chloride- Electrolyte
• Glucose Solution- not Electrolyte
• Sucrose Solution- not Electrolyte
Thursday 1 September 2011
Wednesday 17 August 2011
Tuesday 16 August 2011
Tuesday 17 May 2011
Homologous series
Describe a 'family' of similar hydrocarbons. Each member by changing by an additional -CH2 group.
Tuesday 10 May 2011
Test for Water
anhydrous Copper sulphate (white) turns blue if water is present.
CuS04(s)------->Cus04-5H20
Anhydrous H20 Hydrated
CuS04(s)------->Cus04-5H20
Anhydrous H20 Hydrated
Tuesday 22 March 2011
Test for Gases
Test for Ammonia Gas, NH3 (g)
Ammonia:
1) Has no colour.
2) Has a characteristic pungent smell.
3) Will turn moist red litmus paper blue,
and moist universal indicator paper blue.
It is alkaline in water, pH = 11.5.
4) Will put out a lit splint.
Test for Carbon Dioxide Gas, CO2(g).
Carbon dioxide:
1) Has no colour or smell.
2) Will put out a lit splint.
3) Will turn moist blue litmus paper red,
and moist universal indicator paper orange.
In water it forms carbonic acid (H2CO3), it is a weak acid (see Carbon Cycle).
Test for Chlorine Gas, Cl2(g).
Chlorine:
1) Is green-yellow in colour.
2) Has a pungent choking smell.
3) Will turn moist litmus or universal indicator paper red,
and then bleach it white.
4) Will put out a lit splint.
Test for Oxygen Gas, O2(g).
Oxygen:
1) Has no colour or smell.
2) Has no effect on moist litmus paper
or moist universal indicator paper, it is neutral.
3) Will relight a glowing splint.
Test for Hydrogen Gas, H2(g).
Hydrogen:
1) Has no colour or smell.
2) Has no effect on moist litmus paper
or moist universal indicator paper - it is neutral.
3) Burns with a characteristic 'pop'.
Ammonia:
1) Has no colour.
2) Has a characteristic pungent smell.
3) Will turn moist red litmus paper blue,
and moist universal indicator paper blue.
It is alkaline in water, pH = 11.5.
4) Will put out a lit splint.
Test for Carbon Dioxide Gas, CO2(g).
Carbon dioxide:
1) Has no colour or smell.
2) Will put out a lit splint.
3) Will turn moist blue litmus paper red,
and moist universal indicator paper orange.
In water it forms carbonic acid (H2CO3), it is a weak acid (see Carbon Cycle).
Test for Chlorine Gas, Cl2(g).
Chlorine:
1) Is green-yellow in colour.
2) Has a pungent choking smell.
3) Will turn moist litmus or universal indicator paper red,
and then bleach it white.
4) Will put out a lit splint.
Test for Oxygen Gas, O2(g).
Oxygen:
1) Has no colour or smell.
2) Has no effect on moist litmus paper
or moist universal indicator paper, it is neutral.
3) Will relight a glowing splint.
Test for Hydrogen Gas, H2(g).
Hydrogen:
1) Has no colour or smell.
2) Has no effect on moist litmus paper
or moist universal indicator paper - it is neutral.
3) Burns with a characteristic 'pop'.
Bromide, Iodide, Chloride
Bromide, Iodide, Chloride were all added with nitric acid and then nitrate.
This is the before and after:
This is the before and after:
Friday 18 March 2011
Images: Chemical Testing
(Title is one above picture)
(To clean we sterilized in acid and then burnt off waste with the fire
Calcium:
Ca 2+ reacting with fire.
Lithium:
Li 2+ reacting with fire
Sodium:
Na 2+ reacting with fire
Copper:
Cu 2+ reacting with fire
Potassium:
K+ reacting with fire
(To clean we sterilized in acid and then burnt off waste with the fire
Calcium:
Ca 2+ reacting with fire.
Lithium:
Li 2+ reacting with fire
Sodium:
Na 2+ reacting with fire
Copper:
Cu 2+ reacting with fire
Potassium:
K+ reacting with fire
Monday 14 March 2011
Reactions and Products
During chemical reactions atoms become bounded (joined) together in new ways.
Magnesium + copper oxide = magnesium Oxide + Copper
Chemical reactions are different to physical changes. In physical changes, atoms remain bounded in the same way before and after a change.
Chemical Changes/ chemical reactions.
In chemical reactions new substances are formed. We call the starting materials reactants and the substances that are formed: products.
During chemical changes (reactions) different atoms become bonded.
Chemical bonds are not easy to break.
Because of this chemical changes are usually difficult to reverse (It is difficult to change product back into reactants) e.g. we cannot “un-burn” magnesium, and we cannot un-bake a cake :)
Magnesium + copper oxide = magnesium Oxide + Copper
Chemical reactions are different to physical changes. In physical changes, atoms remain bounded in the same way before and after a change.
Chemical Changes/ chemical reactions.
In chemical reactions new substances are formed. We call the starting materials reactants and the substances that are formed: products.
During chemical changes (reactions) different atoms become bonded.
Chemical bonds are not easy to break.
Because of this chemical changes are usually difficult to reverse (It is difficult to change product back into reactants) e.g. we cannot “un-burn” magnesium, and we cannot un-bake a cake :)
Naming Simple compounds
Magnesium oxygen = magnesium oxide
Sodium chlorine = sodium chloride
Without oxygen – ide
With oxygen – ate
Sodium chlorine = sodium chloride
Without oxygen – ide
With oxygen – ate
Relative Atomic Mass (R.A.M)
it is not strictly true to say that elements consist of one type of atom.
Natural samples of elements are often a mixture of isotopes. About 1% of natural carbon – 13
12C6 99% 1%13C6
Relative atomic mass
RAM – (AR)
12C6 - 12 is the relative atomic mass
The deflection in the mass spectrum varies with the mass of the atom.
However this does not tell us the mass in grams.
What it tells us is the relative masses of atoms – or relative atomic mass RAM
The element carbon is the atom against which the mass of all other atoms are compared. Carbon is given a RAM value of 12
Calculating RAM of isotopes
Many natural elements are a mixture of isotopes
This means that when we react atoms of an element we are using a mixure of atoms with different mass numbers
Natural samples of elements are often a mixture of isotopes. About 1% of natural carbon – 13
12C6 99% 1%13C6
Relative atomic mass
RAM – (AR)
12C6 - 12 is the relative atomic mass
The deflection in the mass spectrum varies with the mass of the atom.
However this does not tell us the mass in grams.
What it tells us is the relative masses of atoms – or relative atomic mass RAM
The element carbon is the atom against which the mass of all other atoms are compared. Carbon is given a RAM value of 12
Calculating RAM of isotopes
Many natural elements are a mixture of isotopes
This means that when we react atoms of an element we are using a mixure of atoms with different mass numbers
Structure of Diamond
The structure of diamond
The giant covalent structure of diamond
Carbon has an electronic arrangement of 2,4. In diamond, each carbon shares electrons with four other carbon atoms - forming four single bonds.
In the diagram some carbon atoms only seem to be forming two bonds (or even one bond), but that's not really the case. We are only showing a small bit of the whole structure.
This is a giant covalent structure - it continues on and on in three dimensions. It is not a molecule, because the number of atoms joined up in a real diamond is completely variable - depending on the size of the crystal.
________________________________________
Note: We quoted the electronic structure of carbon as 2,4. That simple view is perfectly adequate to explain the bonding in diamond. If you are interested in a more modern view, you could read the page on bonding in methane and ethane in the organic section of this site. In the case of diamond, each carbon is bonded to 4 other carbons rather than hydrogens, but that makes no essential difference.
________________________________________
How to draw the structure of diamond
Don't try to be too clever by trying to draw too much of the structure! Learn to draw the diagram given above. Do it in the following stages:
Practise until you can do a reasonable free-hand sketch in about 30 seconds.
The physical properties of diamond
Diamond
• has a very high melting point (almost 4000°C). Very strong carbon-carbon covalent bonds have to be broken throughout the structure before melting occurs.
• is very hard. This is again due to the need to break very strong covalent bonds operating in 3-dimensions.
• doesn't conduct electricity. All the electrons are held tightly between the atoms, and aren't free to move.
• is insoluble in water and organic solvents. There are no possible attractions which could occur between solvent molecules and carbon atoms which could outweigh the attractions between the covalently bound carbon atoms.
The structure of graphite
The giant covalent structure of graphite
Graphite has a layer structure which is quite difficult to draw convincingly in three dimensions. The diagram below shows the arrangement of the atoms in each layer, and the way the layers are spaced.
Notice that you can't really draw the side view of the layers to the same scale as the atoms in the layer without one or other part of the diagram being either very spread out or very squashed.
In that case, it is important to give some idea of the distances involved. The distance between the layers is about 2.5 times the distance between the atoms within each layer.
The layers, of course, extend over huge numbers of atoms - not just the few shown above.
You might argue that carbon has to form 4 bonds because of its 4 unpaired electrons, whereas in this diagram it only seems to be forming 3 bonds to the neighbouring carbons. This diagram is something of a simplification, and shows the arrangement of atoms rather than the bonding.
The giant covalent structure of diamond
Carbon has an electronic arrangement of 2,4. In diamond, each carbon shares electrons with four other carbon atoms - forming four single bonds.
In the diagram some carbon atoms only seem to be forming two bonds (or even one bond), but that's not really the case. We are only showing a small bit of the whole structure.
This is a giant covalent structure - it continues on and on in three dimensions. It is not a molecule, because the number of atoms joined up in a real diamond is completely variable - depending on the size of the crystal.
________________________________________
Note: We quoted the electronic structure of carbon as 2,4. That simple view is perfectly adequate to explain the bonding in diamond. If you are interested in a more modern view, you could read the page on bonding in methane and ethane in the organic section of this site. In the case of diamond, each carbon is bonded to 4 other carbons rather than hydrogens, but that makes no essential difference.
________________________________________
How to draw the structure of diamond
Don't try to be too clever by trying to draw too much of the structure! Learn to draw the diagram given above. Do it in the following stages:
Practise until you can do a reasonable free-hand sketch in about 30 seconds.
The physical properties of diamond
Diamond
• has a very high melting point (almost 4000°C). Very strong carbon-carbon covalent bonds have to be broken throughout the structure before melting occurs.
• is very hard. This is again due to the need to break very strong covalent bonds operating in 3-dimensions.
• doesn't conduct electricity. All the electrons are held tightly between the atoms, and aren't free to move.
• is insoluble in water and organic solvents. There are no possible attractions which could occur between solvent molecules and carbon atoms which could outweigh the attractions between the covalently bound carbon atoms.
The structure of graphite
The giant covalent structure of graphite
Graphite has a layer structure which is quite difficult to draw convincingly in three dimensions. The diagram below shows the arrangement of the atoms in each layer, and the way the layers are spaced.
Notice that you can't really draw the side view of the layers to the same scale as the atoms in the layer without one or other part of the diagram being either very spread out or very squashed.
In that case, it is important to give some idea of the distances involved. The distance between the layers is about 2.5 times the distance between the atoms within each layer.
The layers, of course, extend over huge numbers of atoms - not just the few shown above.
You might argue that carbon has to form 4 bonds because of its 4 unpaired electrons, whereas in this diagram it only seems to be forming 3 bonds to the neighbouring carbons. This diagram is something of a simplification, and shows the arrangement of atoms rather than the bonding.
Moles and Displacement Reactions
Moles and Molar Mass.
Molar Mass:
1 mole of Mg: 24g
1 mole of C: 12g
Etc. etc.
No. moles = mass ÷ R.A.M
For example:
Displacement reactions:
A more reactive halogen will displace a less reactive halide from its compounds in solution
Halogen atom = halide ion
Fluorine F = Fluoride F-
Chloride Cl = Chloride C-
Experiment when filled a huge measuring beaker with water and added alkaline, universal indicator and then dry ice:
Molar Mass:
1 mole of Mg: 24g
1 mole of C: 12g
Etc. etc.
No. moles = mass ÷ R.A.M
For example:
Displacement reactions:
A more reactive halogen will displace a less reactive halide from its compounds in solution
Halogen atom = halide ion
Fluorine F = Fluoride F-
Chloride Cl = Chloride C-
Experiment when filled a huge measuring beaker with water and added alkaline, universal indicator and then dry ice:
About Moles
The mole
The ‘mole’ is simply a quantity (like a dozen)
1 mole = 6 x 10(23) or 600000000000000000000000
1 mole – Mg = 24g
1 mole – C = 12g
1 mole – S = 32g
1 mole – Au = 197g
The mass of a mole is their overall mass – periodic table
The ‘mole’ is simply a quantity (like a dozen)
1 mole = 6 x 10(23) or 600000000000000000000000
1 mole – Mg = 24g
1 mole – C = 12g
1 mole – S = 32g
1 mole – Au = 197g
The mass of a mole is their overall mass – periodic table
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