What is an independent variable?
the variable you change
What is a dependent variable?
The dependent variable is the variable that is measured
What is a controlled variable?
A controlled variable is a variable that stays the same throughout the experiments
Hypothesis of the enzyme
The higher the temperature the faster the enzyme will reach its optimum temperature
equipment for lipase
Water baths at different temperatures
Measuring cylinder
10 test tubes
Thermometer
Stirring rod
Stop watch
milk
sodium carbonate
lipase
phenolphthalein
method for the lipase test
Set up water baths at different temperatures.
Put milk, phenolphthalein, and sodium carbonate into a test tube (it turns pink).
Place the test tube in the water bath to warm up.
Measure some lipase.
Add the lipase and start the timer.
Stir until the mixture goes colourless.
Stop the timer and record the result.
Repeat for all temperatures 3 times
hypothesis for agar cube
The smaller the agar cube, the faster it will diffuse
equipment for agar cube
6 petri dishes, agar cube, ruler, knife, two different solutions
method for the agar cube
- Cut agar cubes into different sizes.
- Measure each cube.
- Put one cube in the acid and start the timer.
- Wait for the colour to disappear.
- Record the time.
- Repeat for all sizes and compare which took the longest.
hypothesis for plant experiments
There is no difference in the mean height of plants with fertiliser and without fertiliser
equipment for a plant experiment
10cm by 10cm quadrat on a transparent acetate sheet
* compass
* 1m ruler
* string
* drawing pin
* clipboard
* light meter
method for plant experiment
Set up two groups of plants: one with fertiliser, one without.
Keep everything else the same (water, light, soil).
Grow the plants for a few weeks.
Measure the height of each plant.
Use a t-test to compare the two groups.
hypothesis energy content of food
Foods with more calories will release more energy when burned
equipment for food test
Food sample & mounted needle
Boiling tube & clamp/stand
Water & measuring cylinder
Thermometer
Balance
Bunsen burner
Safety googles
method for food test
Measure the mass of the food.
Skewer the food on a mounted needle.
Pour a known amount of water into a boiling tube and record its initial temperature.
Burn the food under the boiling tube.
Record the final temperature of the water.
equipment for an alcohol test
Spirit/alcohol burner
Thermometer
Calorimeter or flask
Measuring cylinder
Balance
Clamp & stand
method for the alcohol test
Set up the flask in the clamp above the burner.
Add 80 cm³ of water to the flask.
Record starting temperature.
Light the burner and stir the water while heating for 2–3 minutes.
Extinguish the flame and record the final temperature.
Calculate temperature change (ΔT).
Repeat 3 times for each alcohol.
hypothesis for circuit
The resistance of the LDR decreases as the voltage across it increases
equipment for the circuit
LDR
Power supply
Voltmeter & Ammeter
Wires & Switch
Lamp
method for the circuit
Close the switch and turn on the power supply.
Start at 2 V and record voltage, current, and meter readings.
Increase the voltage by 2 V each time and repeat measurements for all desired voltages.
Turn off the power and open the switch.
Calculate LDR resistance for each voltage.
Repeat the whole process two more times
