Module 5 Practicals

Question 1

Determine the specific heat capacity of a material
- Method (5)
- Graphs and Calculations (4)
- Safety (1)
- Validity (2)

Answer 1

• Measure the mass of the aluminium block using a balance
• Place a thermometer and an immersion heater into the aluminium block and connect the immersion heater to a circuit containing a power supply, an ammeter and a voltmeter
• Before switching on the power supply, record the temperature of the aluminium block
• Switch on the power supply and simultaneously start a stopwatch
• Record the voltage, the current and the temperature of the block every 30s for 5 minutes
• Calculate the power at each interval using P = IV
• Calculate the work done at each internal using W = Pt (where t = 30s)
• Plot a graph of cumulative work done against temperature
• • Line of best fit should be a straight line through the origin
• • E = mcΔθ (y=mx)
• Divide gradient by mass of block to find specific heat capacity
• The immersion heater can get very hot
• Insulate the aluminium block to reduce heat loss
• A greater range of temperatures will reduce the percentage uncertainty

Question 2

Determine the Specific Latent Heat of Fusion
- Method (5)
- Graphs and Calculations (3)

Answer 2

• Place a known mass of ice into two funnels, above two beakers
• Place an electric heater in each funnel, connecting one heater to a power supply, whilst leaving the other with no power source
• Determine the power of the power supply using P = IV
• Switch on the heater in the first funnel and switch it off after 15 mins
• Measure the mass of the water in each beaker
• L = E/Δm
• Δm = mass of water in first beaker - mass of water in second beaker
• (difference in masses is equal to the mass of water that has been melted due to electrical energy input)

Question 3

Investigating the relationship between pressure and volume
- Method (4)
- Graphs and Calculations (1)
- Safety (3)
- Validity (2)

Answer 3

• Attach a pressure gauge to a valve (connected to a foot pump) and connect this to an air column that contains oil
• Start with the valve open and pump up the apparatus to a high pressure and close the valve
• Record the volume of air and the pressure value
• Repeatedly release the valve slowly to reach the next data point and record the data
• Plot a graph of 1/volume against pressure
• Wear eye protection
• Do not exceed the maximum pressure
• Watch for any leaks that may eject oil
• Wait a couple of minutes before taking readings as compressing the air warm it up slightly, so the gas must cool to room temperature before measurements are taken
• Release the valve slowly to ensure the temperature remains constant as gas cools as it expands

Question 3

Estimate a value for absolute zero from gas pressure and volume
- Method for Volume (3)
- Method for Pressure (3)
- Rest of Method (4)
- Graphs and Calculations (1)
- Safety (2)
- Validity (1)

Answer 3

• Seal a capillary tube, containing a sample of air trapped by a small amount of sulphuric acid, at one end
• Attach a 30cm ruler to the capillary tube using elastic bands
• Place the capillary tube into a large beaker full of boiling water, with the open end facing upwards
• Place a bung with connective tubing into the neck of a flask, making sure it is tight
• Attach a connective tubing to the bourdon gauge
• Place the flask into a large beaker of boiling water
• Measure the temperature of the water using a thermometer
• Record the length of the air sample as indicated by the ruler/pressure on the bourdon gauge
• Decrease the temperature of the water by adding ice
• Continuously record the temperature and length of air sample/pressure at regular intervals until the water reaches room temperature
• Plot a graph of length/pressure against temperature
• • L/p = mθ + c
• • X intercept = absolute zero
• Take care when handling boiling water
• Handle capillary tube carefully as sulphuric acid is corrosive
• Ensure the ruler is attached so that the 0cm mark is at the very start of the length of air sample

Question 4

Investigating the relationship between pressure and volume
- Method (7)
- Graphs and Calculations (4)
- Safety (2)
- Validity (2)

Answer 4

• Take the plunger out of a syringe and measure the syringe’s internal diameter using a vernier calliper
• Place the plunger back in the syringe and draw in 5 cm3 of air
• Place tubing over the syringe nozzle and pinch it shut using a clip
• Set up a clamp stand and attach the syringe to it so the plunger is pointing downwards
• Attach a string to the end of the plunger, leaving a loop
• Attach a 100g mass holder to this loop and record the volume of air in the syringe
• Keep adding masses and recording the volume until enough readings taken
• Calculate the cross sectional area of the syringe
• Calculate the force exerted by each mass at each recording
• Calculate the pressure exerted on the gas at each recording using P = F/A
• Plot a graph of 1/volume against pressure
• Be careful if masses drop
• Use counterweight on clamp stand
• Make sure the pinch is as close to the nozzle as possible
• Subtract value for atmospheric pressure from each pressure reading

Question 5

Estimating the work done by a gas as its temperature increases
- Method (2)
- Graphs and Calculations (5)
- Safety (2)

Answer 5

• Same as for Estimate a Value for Absolute Zero: for Volume
• Measure the internal diameter of the capillary tube using a vernier calliper
• Calculate cross sectional area of capillary tube
• Calculate volume of air sample at each length using V = LA
• Plot a graph of volume against temperature
• Work done = pΔV where p = atmospheric pressure, so Work done ∝ ΔV
• Therefore (from graph) as temp increases, work done on gas also increases
• Take care when handling boiling water
• Handle capillary tube carefully as sulphuric acid is corrosive

Question 5

Investigate Circular Motion Using a Whirling Bung
- Method (5)
- Graphs and Calculations (2)
- Safety (2)

Answer 5

• Tie one end of a string to a rubber bung and attach a weight to the other end of the string
• Mark the point where you will hold the string and measure the length of the string that will spin around (the radius)
• Whirl the bung in a horizontal circle at a constant speed to ensure the radius stays constant
• Measure the time for 10 revolutions
• Repeat the experiment by adding different weights but keeping the radius constant
• Calculate the speed of the bung, using v = distance/time (v = 20πr/t)
• Plot a graph of force (weight) against v2
• • Gradient = m/r
• • Multiply gradient by r to find mass of bung
• Wear eye protection
• Conduct in an open space

Question 6

Investigate the factors affecting simple harmonic motion
- Method for Simple Pendulum (7)
- Method for Mass Spring System (6)
- Graphs and Calculations (3)
- Safety (3)
- Validity (2)

Answer 6

• Attach a ball bearing to a string and attach this to a clamp stand
• Adjust the length of the string until it is 1m
• Wait until the bob stops moving completely and place a fiducial marker directly underneath it
• Pull the pendulum slightly and release it
• As the pendulum passes the marker, start the stopwatch and time 10 full oscillations
• Repeat this twice more and calculate a mean time
• Repeat the whole experiment, reducing the length of the string by a fixed amount each time
• Attach a spring to a clamp stand and attach a mass holder to the spring
• Wait until the spring stops moving completely and place a fiducial marker directly opposite it
• Pull the spring down slightly and release it
• As the bottom of the mass holder passes the marker, start the stopwatch and time 10 full oscillations
• Repeat this twice more and calculate a mean time
• Repeat the whole experiment, adding mass by a fixed amount each time
• Divide the mean time to get time period
• Simple Pendulum: Plot a graph of T2 against I
• • T^2 = (4π2/g) L
• Mass Spring System: Plot a graph of T2 against m
• • T^2 = (4π2/k) m
• Be careful about masses dropping
• Place a counterweight on the clamp stand
• Wear eye protection when using springs
• Using a fiducial marker reduces uncertainty in timing
• Make sure the angle of oscillation is small (<10°)

Question 7

Observing Damped Oscillations
- Method (7)
- Graphs and Calculations (3)
- Safety (3)
- Validity (4)

Answer 7

• Attach a spring to a clamp stand and attach a 500g mass to the spring
• Fix a ruler to the clamp stand
• Wait until the spring stops moving completely and place a fiducial marker directly opposite it
• Pull the spring down slightly and release it
• As the bottom of the mass holder passes the marker, start the stopwatch and time 10 full oscillations
• Pull the spring down slightly and release it again, recording the amplitude the spring is pulled to
• Measure the maximum amplitude of the spring at the start of every oscillation for at least 10 oscillations
• Divide mean time by 10 to get time period
• Calculate frequency of oscillations using f = 1/T
• Plot a graph of maximum amplitude against number of oscillations
• • Line of best fit should be an exponential decay curve
• Be careful about masses dropping
• Place a counterweight on the clamp stand
• Wear eye protection when using springs
• Repeat measuring amplitude three time and calculate mean values for maximum amplitude at each oscillation
• Use a sensor to more accurately record amplitudes
• Using a larger mass increased the time period, making measurements easier
• Read at right angles to the ruler to avoid parallax error

Question 8

Observing Forced Oscillations
- Method (7)
- Graphs and Calculations (2)
- Safety (2)

Answer 8

• Attach a vibration generator from a clamp stand and hang a spring directly below
• Attach a mass to the spring
• Place a position sensor directly beneath the spring set up
• Wait until the spring stops completely, then measure the distance from the bottom of the mass to the sensor
• Turn on the signal generator and set it to a frequency lower than the natural frequency
• Using the position sensor, record the maximum amplitude of the oscillations above its equilibrium
• Repeat the step above, increasing the frequency by 10Hz each time
• Plot a graph of maximum amplitude against frequency
• Resonant frequency = frequency when max amplitude reaches its peak
• Be careful about masses dropping
• Place a counterweight on the clamp stand