Physics Grade 10 Gas laws Isoprocesses Investigation sheet mark scheme

Question

Answer

Mark

Additional Guidance

1

a)(i)

a)(ii)

a)(iii)

At constant temperature, pressure and volume are inversely proportional

As the volume increases, the pressure decreases. As the volume decreases, the pressure increases.

Correct value and unit

1

2

1

[4]

b)

table present with 21 sets of readings (rows) for V and P                   1

Two columns headed V/ml, P/kPa                                                                                                                                      

V values of 20…..60 ml in steps of 2 ml and P values present

1

1

1

[3]

Due to limitations of the equipment, it may not be possible to take 21 sets of measurements

c)

axes labelled with V/ml on x axis and P/kPa on y axis

plots occupying at least half the grid  

all plots correct to Ѕ small square

                                                                                                                                                                      1

1

1

1

[3]

d)

good line judgement and quality of line (line of best fit)

Correct relationship between pressure and volume from their results;

Agreement or not agreement with Boyle’s law

1

1

1

[3]

thin, continuous line, drawn with ruler if straight, smooth if curved, preferably with pencil

It may not be evident that it is an inverse proportion

e)

- Difficult to keep the plunger in a steady position (difficult to get an accurate reading of the volume)

- Tube was too long, adding more volume to the one measured in the syringe

- Temperature may not be constant (for example, touching the syringe with hands)

- Poor calibration of the instruments

- The pressure sensor had a relatively shorter range and so limited the number of experimental points

2

[2]

One mark for each answer

Accept any other valid answer

f)

-1

1

[1]

.

g)

The larger the tube, the bigger will the uncertainty in the measurement of the volume be (the real volume is bigger than the one measured in the syringe)

2

[2]

h)

- Use a shorter tube to connect the syringe to the sensor to decrease the difference between the real volume and the volume measure in the syringe

- Insulate the syringe so the temperature of air inside it is not affected by our hands

- Use a pressure sensor with a wider range so more experimental points can be plotted

-

2

One mark for each answer

Accept any other valid answer