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Planning (a) and (b) in Chemistry
Internal Assessment
The following list
of investigation titles is divided into two groups:
- experiments suitable for planning (a) and (b)
- experiments suitable for planning (b) only.
For each title, a
list of the possible variables is included. Experiments suitable for planning
(a) have at least two independent variables that could be manipulated
during an investigation. The titles are sufficiently specific to give
candidates a sense of direction, but they are not sufficiently specific to serve
as a research question. Candidates will have to modify the statement to make
it more specific and focused. In most cases, this will involve indicating the
variable(s) chosen for investigation. Where the title completely specifies
the problem, and only one or no variables can be manipulated, the experiment
is listed for planning (b) only. If the experiment is to be used to
assess planning (a), candidates should not be given information
about the possible variables, since one aspect of planning (a) concerns
the candidate's ability to select the relevant variables without help
from the teacher.
Variables are things
we measure, control or manipulate in an investigation. Independent variables
are those that are manipulated, whereas dependent variables are measured or
registered. The variable that is selected for manipulation is independent,
the variable that depends on the manipulation is dependent. Thus, in a
calorimetry investigation, where a candidate measures the temperature every
30 seconds, time is the independent variable, and temperature is the
dependent variable. Similarly, in a rate investigation, where the candidate
measures the times taken to collect certain volumes of gas, volume is
independent, and time is dependent.
Investigations Suitable for Planning (a)
and (b)
Click here for a description of the planning
criteria.
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1. Investigate the volume of a drop
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Dependent:
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Volume or mass of liquid
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Independent:
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Nature of liquid, includes mass, density, viscosity (these
cannot be separated)
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Temperature
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Material of dropper
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Size of opening
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Angle of delivery
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Speed of delivery
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Height of water column
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Pressure (external)
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Note: This is a very simple experiment suitable as a first
exposure to practise the skills associated with planning (a) and (b).
Any of the first seven independent variables can be investigated.
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2. Investigate the height of a liquid in a capillary
tube
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Dependent:
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Height of liquid
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Independent:
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Nature of liquid
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Diameter of tube
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Material of tube
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Angle of tube
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Temperature
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Overall length of tube
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Depth of capillary tube in the liquid
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Note: Suitable for practice for planning (a) and (b).
Any of the independent variables could be tested.
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3. Investigate factors influencing the solubility of
salts
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Dependent:
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Mass of solute
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Independent:
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Volume or mass of water
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Temperature
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Anion
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Cation
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Relation of charges of the ions
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Note: Candidates will probably control the first independent
variable and can manipulate any of the last three.
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4. Investigate the catalysed decomposition of
hydrogen peroxide
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Dependent:
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Some measure of change of concentration of a reactant or
product (volume of gas, decrease in mass, or concentration of hydrogen
peroxide)
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Independent:
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Relative quantity of catalyst
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Concentration of hydrogen peroxide
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Other transition metal oxides
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Other manganese compounds
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Oxides or metals
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State of division
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Heterogeneous or homogeneous catalysis
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Temperature
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Note: Temperature will probably be controlled. Any of the
other independent variables can be investigated.
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5. Investigate exposure to radiation
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Dependent:
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Counts per unit time
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Independent:
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Type of radiation
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Type of barrier
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Thickness of barrier
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Distance between source and detector
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Strength of magnetic field
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Angle between detector and source
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Time of counting
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Temperature
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Note: Any of the independent variables can be easily
manipulated, apart from temperature which will probably be controlled.
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6. Investigate the rate of electroplating a metal
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Dependent:
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Quantity of metal deposited
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Independent:
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Time
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Temperature
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Concentration of solution
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Identity of metal
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Size of electrode
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Voltage
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Current
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Note: Any of the independent variables could be investigated.
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7. Investigate the equilibrium reaction between an
alkanoic acid and an alkanol
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Dependent:
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Quantity of ester (or change in concentration of acid or
alkanol)
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Independent:
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Initial concentrations of acid and alkanol
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Time elapsed
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Temperature
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Nature of acid
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Nature of alkanol
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Method of measurement
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Note: Any of the first five independent variables could be
manipulated, but this presents a difficult and time-consuming experiment. It
would be easier for the teacher to direct the candidates to measure the
amounts of acid, and to grade this for planning (b) only.
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8. Investigate the effect of acid rain on building
materials
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Dependent:
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Effect on material
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Independent:
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Type of material
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Time of exposure
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Surface area exposed
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Method of measurement
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Temperature
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Nature of acid
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Concentration of acid
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Nature of exposure
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Note: Any of the independent variables could be investigated.
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9. Investigate the conditions affecting the rate of
escape of carbon dioxide from soda water
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Dependent:
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Quantity of gas released
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Independent:
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Time
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Temperature
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Amount of soda water
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Depth of soda water
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Surface area of soda water
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Material of container
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Extent of agitation of the soda water
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Pressure
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Note: Any of the first seven independent variables could be
investigated.
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10. Investigate the amount of a solid that will
dissolve in a solvent
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Dependent:
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Quantity of solid
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Independent:
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Nature of solid
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Quantity of solvent
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Nature of solvent
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Time
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Order of addition
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Temperature
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Stirring
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State of division
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Note: Any of the independent variables could be investigated.
The effect of the last three is probably known in advance.
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11. Investigate the factors influencing the voltage
of an electrochemical cell
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Dependent:
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Voltage
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Independent:
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Size of electrodes
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Distance between electrodes
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Nature of electrodes
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Nature of solution
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Concentration of solution
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Method of measurement
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Nature of ion transfer (salt bridge)
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Note: Any of the first five independent variables could be
investigated.
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12. Investigate the factors affecting retention in
paper chromatography
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Dependent:
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Distance travelled by spot
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Independent:
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Thickness of paper
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Nature of paper
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Eluting solvent
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Size of spot
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Concentration of solute
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Distance solvent travels
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Nature of solute
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Temperature
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Note: Any of the first six independent variables could be
manipulated.
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13. Investigate testing the energy from liquid fuels
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Dependent:
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Temperature change of water
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Independent:
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Construction of calorimeter (including nature of water container,
amount and location of insulation, supply of oxygen)
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Type of fuel
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Amount of fuel/time of burning
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Amount of water
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Distance of flame from calorimeter
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Note: The first set of independent variables will be
manipulated, and perhaps also the type of fuel. The last three independent
variables will need to be controlled.
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14. Investigate the factors affecting the rate of a
reaction
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Dependent:
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Change in concentration
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Independent:
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Nature of reaction
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Concentration of reagents
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Total volume
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Temperature
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State of division (only for heterogeneous reaction)
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Catalysis
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Note: Once a candidate chooses a reaction, at least two other
independent variables could be manipulated.
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15. Determine a property of a gas
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Dependent:
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Measurements
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Independent:
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Property investigated
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Temperature
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Volume
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Pressure
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Amount of gas
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Note: The property chosen should be one where a variable can
be changed. Candidates should have to devise their own methods, rather than
following familiar techniques.
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16. Investigate the factors that affect the rate of
the reaction between sodium thiosulfate and hydrochloric acid
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Dependent:
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Time for visual change
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Independent:
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Total volume of solution
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Concentration of sodium thiosulfate
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Concentration of hydrochloric acid
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Temperature
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Note: Several variables could be manipulated. This is a very
simple variation on investigation 14 (above).
Investigations Suitable for Planning (b) Only
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1. Investigate reactions of hydrocarbons
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Dependent:
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Evidence for reaction
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Independent:
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Temperature
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Time
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Light
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Concentrations
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Specific substrate
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Reagent
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Note: This investigation has been listed for planning (b)
only because the teacher will probably have to give information to the class
about the relevant variables. This experiment has been carried out testing
the possible reactions of bromine solution and the acid-catalysed addition of
water to cyclohexane, cyclohexene, chlorobenzene, and methylbenzene. Any of
the first four variables could be investigated.
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2. Investigate how the densities of specified
solutions vary with their concentrations
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Dependent:
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Mass of solution
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Independent:
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Concentration of solution
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Method of dilution
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Volume of solution
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Note: Only concentration of the solution will be varied. The
challenge is to keep volumes constant by dilution in a volumetric flask,
rather than dilution by adding known volumes of solvent and solution.
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3. Determine the molar mass of a gas
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Dependent:
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Mass
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Independent:
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Volume
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Temperature
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Pressure
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Note: Probably no variable will be manipulated.
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4. Determine the molar mass of a volatile liquid
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Dependent:
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Mass
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Independent:
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Identity of liquid
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Quantity of liquid
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Temperature
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Pressure
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Note: Probably no variable will be manipulated.
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5. Design a hot or cold pack to specifications
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Dependent:
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Temperature change
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Independent:
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Identity of chemical
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Quantity of chemical
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Quantity of water
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Original temperature
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Note: This would probably be done by varying the quantity of
chemical or water, and keeping other factors constant.
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6. Determine the enthalpy of a reaction by a Hess's
law relationship
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Dependent:
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Temperature change
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Independent:
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Nature of reactions
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Quantities of reactants
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Pressure
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Method of measurement
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Note: The independent variables have to be controlled, rather
than varied.
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7. Determine the order of a reaction with respect to
a specified reagent
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Dependent:
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Change of concentration
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Independent:
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Total volume of solution
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Concentration of reagent A
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Concentration of reagent B
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Temperature
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Note: One concentration can be varied while other factors are
kept constant.
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8. Investigate the temperature of a Bunsen burner
flame
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Dependent:
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Temperature (relative rather than absolute)
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Independent:
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Method of measurement
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Location of measurement
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Amount of gas
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Relative amounts of gas and air
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Note: Several factors could be varied, but they would be
difficult to measure.
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9. Investigate the concentration ranges in which
starch and iodine react
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Dependent:
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Evidence for reaction
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Independent:
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Relative concentrations of starch and iodine
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Presence of other substances
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Temperature
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Time
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Note: Candidates are likely to change the first independent
variable.
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10. Investigate the conditions for glucose oxidase
to react with glucose
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Dependent:
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Measured effect
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Independent:
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Measurement method
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Concentration of glucose
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Time
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Temperature
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Quantity of solution
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Presence of other substances in solution
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Note: Candidates are likely to investigate the concentration
necessary for reaction.
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11. Investigate the relationship between the
strength of an egg shell and its composition
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Dependent:
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Measurement of strength
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Independent:
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Method of measurement
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Different eggs
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Size of sample portion
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Analysis of composition
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Note: Candidates will control variables rather than
manipulate them.
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12. Investigate the composition of a common
substance by acid–base titration
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Dependent:
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Volume of titrant
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Independent:
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Identity of analyte
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Quantity of sample
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Concentration of titrant
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Indicator
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Note: Candidates will control variables and specify their
values rather than manipulate them.
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13. Investigate the composition of a common
substance by oxidation–reduction titration
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Variables and evaluation are similar to investigation 12
above.
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14. Investigate how the colour produced by iron(III)
and thiocyanate ions varies with concentrations
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Dependent:
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Absorbance
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Independent:
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Wavelength
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Concentration of Fe(III) ions
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Concentration of thiocyanate ions
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Identity of complex formed
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Note: Candidates will probably vary one concentration or the
other, while keeping other
variables constant.
Note: In addition to the
candidate work, samples submitted for moderation must include the
instructions, written or oral, given to the candidate by the teacher. This
vital information is used by moderators to assess whether the experiment, as
given, was suitable for assessing the criteria.
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