Ensure you highlight anomalies and ignore them in the mean or average calculation.
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Independent variable
Potential difference (voltage)
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Dependent variable
Change in current.
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Control variables
Ensure the same equipment (battery/ ammeter) are used & that the circuit is set up in the same way.
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Findings: what happens to the current when the voltage increases?
As the voltage increases, the current increases. It's increase starts by doubling but as it increased further, it slowed down.
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Why does the current increase as voltage increases?
This is due to current and voltage being directly proportional to eachother. This means a greater voltage results in more electrons flowing through the circuit so the current is higher.
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Resistance calculation
P= I^2 x R
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Percentage error calculation
Percentage = Error uncertainty / reading x 100
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Light emitting diode (LED)
They only allow current to pass in one direction and will only light if the current passes in that direction. They indicate the presence of a current through illumination.
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Power equations
Power= current x voltage
Work done= power x time
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Reproducibility
Repeating the same method with a different set of equipment and comparing the results.
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Reproducibility in the experiment
It's very easy to reproduce because the equipment is easily available and after ensuring all the equipment works correctly, it will mean the results collected can be compared.
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Aim of experiment
To determine the effect of hydrogen peroxide concentration on the rate of reaction of catalase.
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Hypothesis
As the substrate concentration increases, the enzyme, catalase, activity increases.
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Hypothesis explained
This is because there are more substrate molecules to bind to the enzyme's active site. Increasing the substrate concentration won't increase indefinetly; all the active site will be occupied. Rate is expected to slow at 16% substrate concentration.
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Independent variable
Hydrogen peroxide (substrate) concentration.
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Dependant variable
Time taken to reach 30cm3 of oxygen on a gas syringe.
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Control variables
Room temperature bottle of distilled water. Use the same batch of 20% hydrogen peroxide to control pH. Same volume & concentration of yeast catalase (4cm3).
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Findings
When the substrate concentration increases, the rate of reaction decreases.
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Findings explained
This is because there are more substrate molecules to bind to the enzyme's active site due to more collisions occuring.
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Evaluation
Electronic/ digital gas syringe to reduce risk of human error of precision & accuracy.
Light reflection onto the syringe, reducing accuracy.
Mechanical pipette to improve accuracy.
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Repetitions of the experiment
Repeat experiment with over 20% conc. to determine the active site saturation.
Should of repeated experiment more than 3 times as active yeast was used (living organism, great variations).
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Justification of equipment
10cm3 measuring cylinder- easier to read, more precise.
1 batch of H2O2- ensure controls are maintained.
Stopwatch- more exact than analouge watch.
Distilled water- ensure temperature is maintained.
Gas syringe- accuracy/ precision instead of displacement
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Risk assessment 1
H: hydrogen peroxide solution
R: irritant to eyes & skin
P: wear goggles, take care when opening bottles.
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