Atomic Structure
Name the three sub atomic particles with the type of charge they have
proton - positive
electron - negative
neutron - neutral
This technique is used to separate soluble coloured substances.
Paper Chromatography
Substance that do not dissolve in a liquid
insoluble solid
What type of reaction occurs when a compound breaks down into simpler substances?
Decomposition reaction
What is meant by Exothermic reaction?
The temperature of the surroundings increases
Energy of the products is lower than the reactants
Heat is given out
An atom of sodium is written as:
²³₁₁Na
p = ____ n=_____ e=________
p=11
n=12
e=11
A student sets up a paper chromatography experiment.
a) Why is a pencil used to draw the baseline instead of a pen?
b) Why must the solvent level be below the baseline?
a) Pencil is insoluble in the solvent and will not dissolve or run.
b) To prevent the sample spots from dissolving directly into the solvent.
Factors that affect solubility of a substance
Size of the particles
Mass of solid added
What type of reaction occurs when two substances combine to form one product?
Combination reaction
Identify two endothermic reactions from the following
combustion of methane
thermal decomposition of calcium carbonate
neutralisation of hydrochloric acid with sodium hydroxide
photosynthesis
respiration
Thermal decomposition of calcium carbonate
Photosynthesis
Write the electronic configuration of:
i) oxygen (atomic number 8)
ii) magnesium (atomic number 12)
O= 2,6
Mg=2,8,2
A student separates three food colourings: A, B and C.
The chromatogram shows:
A forms one spot
B forms two spots
C forms one spot at the same height as one of B’s spots
a) Which sample is a pure substance?
b) Which sample is a mixture?
c) What does it mean when two spots are at the same height?
d) Which samples contain the same substance?
a) A and C
b) B
c) They are the same substance
d)B and C
Solution in which more substance can be dissolved
Unsaturated solution
Arrange these metals in decreasing order of reactivity:
Zinc, Potassium, Iron, Copper
Potassium, Zinc, Iron, Copper
Identify two exothermic reactions from the following
combustion of methane
thermal decomposition of calcium carbonate
neutralisation of hydrochloric acid with sodium hydroxide
photosynthesis
respiration
Any two:
Combustion of methane
Neutralisation of hydrochloric acid with sodium hydroxide
Respiration
State one difference between Thomson’s model and Rutherford’s model.
In Thomson’s model the positive charge is spread throughout the atom with electrons embedded in it,
whereas in Rutherford’s model the positive charge is concentrated in a small central nucleus and most of the atom is empty space.
A student notices the spots are very large and unclear.
a) Suggest one reason for this.
b) State one improvement.
a) Too much sample was spotted on the baseline.
b) Use a smaller, more concentrated spot and allow it to dry before re-spotting.
Differentiate between saturated and unsaturated solution
Give 2 points
A metal X displaces iron from iron sulfate but does not displace aluminium from aluminium oxide. What can you say about the reactivity of metal X?
It is more reactive than iron but less reactive than aluminium
50 cm³ of dilute acid is mixed with 50 cm³ of dilute alkali.
Initial temperature = 22 °C
Highest temperature = 28 °C
a) Calculate the temperature change.
b) State the type of reaction.
6 °C
Exothermic
a) This scientist discovered the nucleus using the gold foil experiment.
b) State three observations of the scientist
c) State the inference of the experiment
Ernest Rutherford
Most of the alpha particles passed straight through the gold foil.
Some alpha particles were deflected through small angles.
A very small number of alpha particles were deflected through large angles / bounced back.
Inference
The atom is mostly empty space.
The positive charge and most of the mass are concentrated in a very small, dense nucleus at the centre of the atom.
Explain the steps of separating the coloured mixture
Draw a straight baseline in pencil near the bottom of the chromatography paper.
Place a small spot of the coloured mixture on the centre of the baseline and allow it to dry.
Pour a small amount of solvent into a beaker so that the level is below the baseline.
Suspend the paper in the beaker so that the bottom touches the solvent.
Cover the beaker with a lid to prevent evaporation.
Allow the solvent to move up the paper and separate the colours.
Remove the paper before the solvent reaches the top.
Mark the solvent front with a pencil and allow the paper to dry.
Calculate the concentration of salt in solutions in g/cm3
a) Mass of salt in Sol P = 2 g ; Volume of water = 10cm3
b) Mass of salt in Sol Q = 3.5 g ; Volume of water = 70 cm3
Concentration of P=2/10=0.2 g/cm³
Concentration of Q=3.5/70=0.05 g/cm³
Three metals P, Q, and R are added separately to copper sulfate solution.
P and Q displace copper, but R does not.
Which metal is the least reactive?
R
A student wants to determine whether the reaction between dilute hydrochloric acid and sodium hydroxide is exothermic.
Plan an experiment that the student could carry out in the laboratory.
Your answer should include:
apparatus needed
the method
the measurements to be taken
the expected result
Polystyrene cup (in a beaker) with lid
Thermometer
Measuring cylinder (or pipette)
Stirring rod
Dilute hydrochloric acid
Dilute sodium hydroxide
Method
Measure a fixed volume (e.g. 25 cm³) of dilute hydrochloric acid using a measuring cylinder.
Pour the acid into the polystyrene cup and record its initial temperature.
Measure the same volume (25 cm³) of dilute sodium hydroxide and record its initial temperature.
Add the sodium hydroxide to the acid in the cup.
Stir the mixture and place the lid on the cup.
Record the highest temperature reached.
Expected result - Exothermic