Edexcel Chemistry IGCSE 1C Unofficial Mark Scheme 19th May 2016

Is the answer to 6c not 10 degrees Celcius
I remember the question was 'what is the maximum rise in temperature' and the temperature started off at 23 degrees and ended at 33, 33-23= 10
Correct me if im wrong

Eventually disappears, moves, floats on surface.

I can't exactly remember.

Tell me the questions which I'm missing out - I'll add them in. Please try your best to remember the rough question number.

1.a)
Condensation. (1)

1.b)
Energy: average ke of particles decreases.
Arrangement: the intermolecular spaces decrease (as some intermolecular
forces between particles start to form).
Movement: particles in liquids slide over each other. (3)

2.a)
Filtration. (1)

2.b)
Arrow drawn into solvent inside beaker.
Arrow drawn onto chromatography paper.
Arrow drawn onto the line on the chromatography paper. (3)

2.c)
There are for 4 dyes present in the substance as the original substance
dissolved into the solvent and 4 dyes were drawn up. (1)

3.a)
Hydrogen molecule bonding - two circles that cross over each other and at the
point of intersection there is a cross and a dot. The circles both have letters H
inside of them. (1)

3.b)
Element in the air - argon. (1)

3.c)
Compound present in unpolluted air - H2O (water) or CO2 (carbon dioxide). (1)

3.d)
Isotopes are atoms with specific number of neutrons independent to the number of protons that defines the element. (2)

3.e)
H1 - 1 proton, 0 neutrons, 1 electron.
H2 - 1 proton, 1 neutron, 1 electron.
H3 - 1 proton, 2 neutrons, 1 electron. (3)

3.f)
Atom with 3 protons - the diagram with 3 dots.
Atom in period 3 - the diagram with 15 dots (phosphorous)
Atom with 15 electrons - diagram with 15 dots (phosphorous)

4.a)
Simple filling in the temperatures - to 1 dp. (4)

4.b)
Max temperature produced by magnesium. (1)

4.c)
Ice used to cool down and condense the water vapour. (1)

4.d)
Products formed - magnesium chloride and hydrogen (gas). (2)

4.e)
Increasing volume of acid to 50cm3 - not so great a rise in temperature as increase in volume of acid means that more energy is required for the same rise in temperature. (2)
4.a)
Copper pile turns black because the oxygen in the air reacts with it in a combustion reaction to form Copper oxide (black solid). (2)

4.b)
The gas is cooled down before it is measured so that its volume can be recorded at rtp (as the original volume had been measured in these conditions). Heated gases = expansion of volume. (1)

4.c)
Why didn't the small heap of copper turn black - because all of the oxygen in the air had been used up in the previous reaction hence no combustion reaction to oxidise copper. (1)

4.d)
Percentage of oxygen - 16.6 (recurring) or 16.7%. (2)

5.a)
In order of reactivity - Q, R, S, P. (4)

6.a)
Graph - draw straight lines of best fit, both lines must intersect. (4)

6.b)
Volume used - 12.5 cm3. (1)

6.c)
33 degrees celcius. (1)

7.a)
Test for presence of water - add to anhydrous copper (II) sulphate, turns white to blue.
OR add to anhydrous cobalt (II) chloride paper, turns blue to pink. (2)

7.b)
Test for purity - physical boiling point test - boils at 100 degrees celsius. (1)

11.a)
Propane. (1)

11.b)
C4H10. (1)

11.c)
W, X, Y. (1)

11.d)
Empirical formula for Y - CH2. (1)

11.d)
A hydrocarbon with a double carbon = carbon covalent bond.
A hydrocarbon is a organic compound made of hydrogen and carbon only. (3)

11.e)
Displayed formula should have only 1 Br atom in it. (1)

11.f)
Condition required - UV light. (1)

16.a)
Draw graph line - steeper and levels off first but at same level. (2)

16.c)
Increase in concentration = increase in particles per unit volume, hence increase in no. of collisions per unit time hence increase in no. of successful collisions per unit time, hence increase in rate of reaction. (3)

For question 4d) can we put 17% rather than 16.7

For 4e) increasing the volume to 50cm3 pretty much everyone I asked , and me, put that the temperature would decrease as it was already in excess so increasing volume would cause the same amount of energy to be released but it would have to spread out across a greater volume so the overall temperature would decrease.

Wasn't the table thing for temperature to the nearest 0.5 degrees so it's not to 1.dp. It was like 47,25,36,43.5,27.5

Wasn't the table thing for temperature to the nearest 0.5 degrees so it's not to 1.dp. It was like 47,25,36,43.5,27.5

Why ice was used?
Describing a covalent bond?
The maximum temperature produced?
Why experiment 1 was faster than experiment 2?

Thanks for doing this btw - really helpful
Anyone got any ideas about the grade boundaries?

Fizzing and Aq solution formed?