REQUIRED PRACTICALS

Question 1

RP1 - Investigation to determine the specific heat capacity of one or more materials(7)

Answer 1

1. Measure and record mass of the metal block
2. Add heater to the block and connect to power pack connected to a joulemeter
3. Add thermometer and record start temperature
4. Turn power pack on and start timer
5. Record temperature and energy transferred after 10 minutes
6. Calculate temperature change
7. Use equation CHANGE IN ENERGY/MASS TIMES CHANGE IN TEMPERATURE=SPECIFIC HEAT CAPACITY

Question 1

Why would the result for specific heat capacity be different to true value?(3)

Answer 1

• Heat loss
• Turning off power supply too early
• Mass/temperature measured incorrectly

Question 2

What would happen to the material the specific heat capacity is being determined for? Examples

Answer 2

• Should be insulated because it prevents heat loss, makes results more accurate
• Bubble wrap or cotton wool

Question 3

What are the control variables for RP1?

Answer 3

1. Mass of block
2. Size of block
3. Material of block
4. Thickness and material of insulation
5. Time block is heated for

Question 4

RP2 - Investigating thermal insulators(7)

Answer 4

1. Boil water in a kettle and add 80cm3 of this water to a beaker
2. Place beaker into larger beaker with a lid
3. Place thermometer through lid
4. Record start temperature
5. Start timer and record temperature at 5,10,15,20 minutes
6. Repeat steps 1-5 with different materials in the gap between smaller and larger beaker
7. Plot a cooling curve of temperature against time

Question 5

What are the control variables for RP2?

Answer 5

• Start temperature of water
• Volume of test liquid
• Material of lid
• Thickness of lid

Question 6

What to use to hold layers of insulation? RP2

Answer 6

Elastic bands

Question 7

What are the advantages of using a digital thermometer? (2)

Answer 7

• Higher resolution
• Less likely to misread results

Question 8

What are the good insulators in RP2?

Answer 8

• Cotton wool and fleece as good insulators because they have pockets of airs

Question 9

What is used as a control RP2?

Answer 9

• A beaker with no insulation

Question 10

How to determine the best insulating material?

Answer 10

• Look for one that temperature dropped the least over a certain time

Question 11

RP3 - Investigating resistance of a wire(6)

Answer 11

1. Set up equipment
2. Place crocodile clips 10cm apart on the length of wire using ruler
3. Turn power on and record current and voltage
4. Calculate resistance using formula R=V/I
5. Repeat for different lengths of wire 20cm, 30cm, 40cm, 50cm
6. Plot a graph of resistance against length

Question 12

RP3 - How could you tell if an ammeter or voltmeter have zero error?

Answer 12

They would show a reading when not connected in a circuit

Question 13

RP3 - What are the 3 control variables when investigating length of wire and resistance?

Answer 13

• Temperature
• Material of wire
• Thickness of wire

Question 14

RP3 - How could the temperature be controlled when investigating resistance?

Answer 14

Turn power supply off between readings to prevent components warming up

Question 15

RP3 - How would you know if your results were precise?

Answer 15

Measurements would be closely grouped together

Question 16

RP3 - What are the hazards in this experiment?

Answer 16

• High current causes wire to melt
• Burns

Question 17

RP3 - What would happen to the variable resistor?

Answer 17

• Would have to be adjusted each time the length of the wire is changed
• it changes the resistance of the wire so that current remains the same so that the temperature of the wire is kept constant

Question 18

RP3 - What happens if the temperature increases?

Answer 18

Resistance increases

Question 19

RP3 - What happens if the thickness of the wire increases?

Answer 19

• Resistance decreases

Question 20

RP4 - Investigating IV characteristics of a resistor/filament lamp/diode(8)

Answer 20

1. Set up equipment
2. Record current and voltage
3. Adjust variable resistor
4. Record new current and voltage
5. Repeat this until you have 5 pairs of readings
6. Swap connections to the battery
7. Repeat steps until you have 5 negative pairs of readings
8. Draw graph of I-V

Question 21

RP4 - What piece of equipment should you use to measure current when investigating the IV characteristics of a diode?


Answer 21

Milliameter

Question 22

RP4 - How do you get negative current and voltage readings?

Answer 22

Swap leads connecting to the power supply

Question 23

RP4 - Why is a variable resistor use when investigating IV characteristics?

Answer 23

To change the resistance in the circuit so more current and voltage pairs can be determined

Question 24

RP4 - What should be controlled?

Answer 24

Temperature - turn power supply off between readings to prevent components from heating up

Question 25

RP5 - determining the densities of regular objects(5)

Answer 25

1. Measure the length, width and height of the object(mm) 2. Calculate the volume in cm3 3. Measure the mass of the object - RESET balance to reduce zero errors 4. Calculate density using equation density=mass/volume 5. Convert from g/cm3 to kg/m3

Question 26

RP5 - determining the densities of irregular objects(6)

Answer 26

1. Fill displacement can with water - align measuring cylinder with spout 2. Add irregularly shaped object slowly into the can, do not drop it from a height 3. Collect displaced water and measure the volume of water displaced 4. VOLUME OF WATER DISPLACED WILL EQUAL THE VOLUME OF OBJECT 5. Measure mass of object 6. Calculate density using density=mass/volume

Question 27

RP5 - determining the densities of liquids(5)

Answer 27

1. Measure mass of empty measuring beaker, using balance 2. Pour 100cm3 of the liquid in the beaker 3. Measure combined mass of the beaker and the liquid 4. LIQUID'S MASS = subtract mass of the beaker from mass of combined beaker and liquid 5. Calculate the density of the liquid using density=mass/volume

Question 28

RP5 - What is zero error?

Answer 28

When a piece of apparatus gives a false reading when the true value is 0

Question 29

RP5 - How can a zero error on a balance be corrected?

Answer 29

Record value on the balance when it should be zero, subtract this value from each mass recorded

Question 30

RP5 - when measuring the volume of an irregularly shaped object how could an error occur?(3)

Answer 30

1. The water level may not be at the same level as the spout 2. Not all displaced water is collected in measuring cylinder 3. Eye position could be too high or low when measuring volume