Year 13 Unit 3 SCIENCE ALL POSSIBLE PRACTICALS

Question 1

Explain the method for the rate of photosynthesis practical (pondweed)

Answer 1

1. Place pondweed in a sodium hydrogen carbonate filled boiling tube, making sure it is fully submerged, takes up more than half of the tube and is clamped.
2. Place a ruler by the LED bulb to know how far the distance is between the light source and the pond weed, move the LED bulb so that it is 10cm away from the pond weed.
3. Cut off a small part of the stem of the pond weed and ensure that all light sources apart from the LED bulb are turned off or blocked.
4. Turn on the LED bulb but let the pondweed get used to the amount of light the LED bulb is giving, therefore wait 3 minutes before counting oxygen bubbles.
5. Start the timer for 1 minute and count the amount of oxygen bubbles that appear then record.
6. Move the pondweed or LED bulb 10cm more further away.
7. Repeat steps 5 and 6 until you have reached 50cm distance between the bulb and pondweed.

Question 2

Plan an investigation to look at the number of daisies in different areas of the campus or in a local park ,by and collect data using quadrats

Answer 2

1. Measure out the area you are going to be researching on using a trundle wheel and calculate the total area.
2. You should split the total area into a 1 m square grid where each square should be coordinated e.g., (1,1), (1,2).
3. Use a random number generator to get random coordinates, you should generate coordinates enough to cover around 5-10% of the total area but 10 is enough.
4. Place quadrats on the coordinates generated and count the daises with it, excluding the daises were half of it is outside of the quadrat, results should be in a table.
5. Calculate the mean number of daises and multiple by the total area to calculate how much daises are in the local park.

Question 3

Plan an investigation to measure current and voltage for a fixed resistor in a circuit.

Answer 3

1. Set up a series circuit that includes a battery, variable resistor, ammeter, fixed resistor and a voltmeter which is parallel to the fixed resistor.
2. Adjust the variable resistor so that the voltage starts at 0.
3. Use the variable resistor to increase p.d by 0.5 or 1 and record new readings.
4. Continue to use variable resistor to increase p.d and record results, up until you have reached 5 p.d.
5. Now reverse power supply connections to get a negative reading and repeat steps 2-4

Question 4

Plan an investigation as to how the resistance of a thermistor varies with temperature

Answer 4

1. Create a series circuit with a battery, ammeter, thermistor and a voltmeter which is parallel to the thermistor.
2. Boil water at 80 degrees Celsius
3. Set the battery at 6 volts and measure the room temperature, initial current, initial voltage and calculating the initial resistance using R = V / I.
4. Add boiling water to a beaker, place a thermometer and thermistor submerged in the beaker, let it settle for 2 minutes.
5. Record the temperature, voltage, amps and calculate resistance.
6. Add cold/tap water to reduce the temperature of the water, it should be 10+ degrees Celsius less than the first reading and record temp, volts, amps and calculate resistance.
7. Continue adding cold water to reduce temp, recording the volts, current and stop when it has reached room temperature again or lower.

Question 5

Plan an investigation on the effect of substrate concentration on an enzyme-catalysed reaction (catalase and hydrogen peroxide)

Answer 5

n/a

Question 6

Plan an investigation involving heating water using different foods as fuels to see which produces the most energy

Answer 6

1. Add 20ml of water to a boiling tube clamped in a clamp stand and record the starting temperature of the water.
2. Place food sample on mounted needle, ignite the food sample using a Bunsen burner and hold the burning food sample under the boiling tube of water until completely burned.
3. Record the final temperature of the water in a table and calculate the change in temperature caused by the burning food sample.
4. Repeat steps 2 and 3 with this food type to increase reliability and calculate the average change in temperature for this food type.
5. Calculate the energy released by this food type using this equation: Energy released (J) = mass of water (g) x rise in temperature (°C) x 4.2 and repeat steps 1-8 with different food types for comparison.