Working Scientifically Worksheets, Questions and Revision

Revision Library

revisionlibrary.co.uk

13+ · Science

CE.S-W1 Working Scientifically

ISEB CE ISEB Common Entrance 13+ Science · Calculator allowed · about 80 minutes

Total Marks

Name: _______________________________ Date: ____ / ____ / ______

Answer ALL questions. Show all your working.

1

Which piece of apparatus should be used to measure the volume of gas produced during a chemical reaction?

A) Measuring cylinder
B) Gas syringe
C) Thermometer
D) Top-pan balance

(Total for Question 1 is 1 mark)

2

A cylinder of hydrogen gas is labelled with a diamond-shaped symbol showing a black flame on an orange background. What hazard does this symbol represent?

A) Toxic
B) Corrosive
C) Flammable
D) Irritant

(Total for Question 2 is 1 mark)

3

State the correct unit that should be used to record each of the following measurements in a school laboratory.

(a)The volume of a liquid poured into a measuring cylinder.(1)

(b)The temperature of the water in a water bath.(1)

(Total for Question 3 is 2 marks)

4

A student reads the volume of liquid in a measuring cylinder. The bottom of the curved meniscus lines up exactly halfway between the 34 cm³ and 36 cm³ graduation marks, which are 2 cm³ apart.

(a)State the volume of liquid in the measuring cylinder.(1)

(b)Give one reason why the student should read the value at eye level, level with the bottom of the meniscus.(1)

(Total for Question 4 is 2 marks)

5

Chidinma is investigating how the length of a pendulum's string affects the time taken for the pendulum to complete 10 full swings.

(a)State the independent variable in this investigation.(1)

(b)State the dependent variable in this investigation.(1)

(Total for Question 5 is 2 marks)

6

Aled is investigating how the concentration of salt solution affects the growth rate of cress seedlings. State three variables, other than the concentration of salt solution, that Aled should control to make this a fair test.

(Total for Question 6 is 3 marks)

7

Match each term to its correct definition by writing the correct letter next to each term.
Terms: 1. Accuracy 2. Repeatability
Definitions:
A. How close a measured value is to the true value.
B. How closely repeated measurements, taken by the same person using the same method and equipment, agree with each other.

(Total for Question 7 is 2 marks)

8

A student measures the time for a trolley to travel down a ramp three times: 2.14 s, 2.09 s and 2.21 s.

(a)Calculate the mean time, giving your answer to 3 significant figures.(2)

(b)State why it is good scientific practice to repeat a measurement more than once.(1)

(Total for Question 8 is 3 marks)

9

Over several decades, both the number of pet cats owned in the UK and the amount of plastic recycled each year have increased. A student concludes that owning more cats causes more plastic to be recycled.

(a)State the type of relationship shown by this data.(1)

(b)Explain why the student's conclusion is not justified.(2)

(Total for Question 9 is 3 marks)

10

Femi investigates the rate of reaction between a 3 cm strip of magnesium ribbon and 50 cm³ of dilute hydrochloric acid. He collects the hydrogen gas produced in a gas syringe and records the total volume of gas collected every 10 seconds.

At t = 30 s he took three repeat volume readings: 41 cm³, 42 cm³ and 55 cm³. After dealing with these readings appropriately, his full set of results was:

Time (s): 0	10	20	30	40	50	60
Volume of gas (cm³): 0	18	32	41.5	48	50	50

(a)Identify the anomalous result from the three repeat readings at t = 30 s, and suggest one possible cause of this anomaly.(2)

(b)Calculate the mean volume at t = 30 s, using only the two consistent (non-anomalous) readings.(2)

(c)State the independent variable and the dependent variable in this investigation.(2)

(d)Calculate the rate of gas production between t = 0 s and t = 20 s, in cm³/s. Give your answer to 2 significant figures.(3)

(e)Calculate the rate of gas production between t = 40 s and t = 60 s. What does this value tell you about the reaction at this time?(3)

(f)State the time at which the reaction appears to have finished, and explain how you know this from the table.(2)

(g)Suggest one improvement Femi could make to his method to increase the accuracy of his volume readings, and explain why it would improve the results.(2)

(h)Identify one hazard in this experiment and state a suitable control measure.(2)

(i)Femi wants to test the hypothesis that increasing the concentration of hydrochloric acid increases the rate of reaction. State two variables he must control to make this a fair comparison between different concentrations.(2)

(j)Calculate the percentage increase in the volume of gas collected between t = 20 s and t = 40 s.(2)

(Total for Question 10 is 22 marks)

11

A student measures the mass of a small rock sample as 47.6 g using a balance and finds its volume to be 18.0 cm³ using the displacement method with a measuring cylinder. Calculate the density of the rock, in g/cm³, giving your answer to 3 significant figures.

(Total for Question 11 is 3 marks)

12

A student measures the length of a metal wire five times using a metre ruler. The results are: 84.2 cm, 84.5 cm, 84.1 cm, 84.6 cm, 84.3 cm.

(a)Calculate the mean length of the wire.(2)

(b)Calculate the range of the results.(2)

(Total for Question 12 is 4 marks)

13

A spring is stretched by forces between 0 N and 10 N. A graph of extension (cm) against force (N) is a straight line through the origin, showing that extension = 0.8 x force, where force is in newtons and extension is in centimetres, for forces up to 10 N.

(a)State the type of relationship shown between the force and the extension.(1)

(b)Use the equation to predict the extension of the spring when a force of 7.5 N is applied.(2)

(Total for Question 13 is 3 marks)

14

In a different investigation, a graph is plotted of the volume of gas produced (cm³) against time (s) for a reaction that slows down over time. A tangent is drawn to the curve at t = 10 s. The tangent passes through the points (0 s, 6 cm³) and (20 s, 30 cm³). Calculate the gradient of the tangent, and use this to state the rate of reaction at t = 10 s, including units.

(Total for Question 14 is 3 marks)

15

A thermometer has graduations every 1 degC. A student takes a single temperature reading of 25 degC. Calculate the percentage uncertainty in this reading, giving your answer to the nearest whole per cent. (Uncertainty = half of the smallest graduation.)

(Total for Question 15 is 3 marks)

16

Before an experiment, a student notices that a top-pan balance reads 0.5 g when there is nothing on it.

(a)State the type of error this represents.(1)

(b)Explain how this error would affect every mass measurement taken using this balance.(2)

(Total for Question 16 is 3 marks)

17

Using the results from Question 10, predict the total volume of gas that would be collected if Femi's experiment were continued to t = 90 s. Explain your answer using ideas about the reactants in the experiment.

(Total for Question 17 is 3 marks)

18

Femi's teacher says that repeating the whole experiment at each concentration and calculating a mean rate would make his conclusion more valid. Explain why using a mean from repeated trials, rather than a single trial, improves the validity of a conclusion.

(Total for Question 18 is 2 marks)

19

A group of pupils wants to investigate how the concentration of hydrochloric acid affects the rate of its reaction with magnesium ribbon. Plan a method they could use to investigate this, including how they would make it a fair test and how they would ensure their results are reliable.

(Total for Question 19 is 6 marks)

20

Evaluate the method used by Femi in Question 10 to investigate the rate of reaction between magnesium and dilute hydrochloric acid. In your answer, comment on the reliability and accuracy of his results and suggest improvements he could make.

(Total for Question 20 is 6 marks)

Mark scheme · CE.S-W1 Working Scientifically

Question 1

B1 B cao
Answer: B) Gas syringe

Question 2

B1 C cao
Answer: C) Flammable

Question 3

(a) B1 cm³ (or dm³) oe
(a) Answer: cm³
(b) B1 degrees Celsius, degC cao
(b) Answer: degC (degrees Celsius)

Question 4

(a) B1 35 cm³ cao
(a) Answer: 35 cm³
(b) B1 to avoid parallax error, which would make the reading look higher or lower than it really is oe
(b) Answer: To avoid parallax error.

Question 5

(a) B1 length of the pendulum string oe
(a) Answer: Length of the pendulum string.
(b) B1 time taken for 10 swings oe
(b) Answer: Time taken for 10 swings.

Question 6

B1 same species/variety and starting size of cress seedling
B1 same volume of solution given to each seedling
B1 any other valid control, e.g. same temperature, same amount of light, same size/type of pot, same length of time
Answer: Any three of: same species/starting size of seedling, same volume of solution, same temperature, same amount of light, same size/type of container, same length of experiment.

Question 7

B1 1-A cao
B1 2-B cao
Answer: 1-A, 2-B

Question 8

(a) M1 (2.14 + 2.09 + 2.21) / 3
(a) A1 2.15 s (3 s.f.) awrt
(a) Answer: 2.15 s
(b) B1 allows an anomaly to be identified and a mean to be calculated, making the result more reliable oe
(b) Answer: It allows anomalies to be spotted and a mean to be calculated, giving a more reliable result.

Question 9

(a) B1 a correlation (positive correlation) oe
(a) Answer: A (positive) correlation.
(b) B1 correlation does not mean one variable causes the other oe
(b) B1 both trends could instead be linked to a third factor, e.g. rising population or greater environmental awareness, rather than cats causing recycling oe
(b) Answer: Correlation does not prove causation; both trends may simply be caused by another factor, such as a growing UK population.

Question 10

(a) B1 55 cm³ cao
(a) B1 a plausible cause, e.g. an air bubble entered the syringe, the bung was briefly loose and gas leaked in, or a misread scale oe
(a) Answer: 55 cm³; possible cause: a gas leak into the syringe or a misread scale.
(b) M1 (41 + 42) / 2
(b) A1 41.5 cm³ cao
(b) Answer: 41.5 cm³
(c) B1 independent variable: time (s)
(c) B1 dependent variable: volume of gas produced (cm³)
(c) Answer: Independent variable: time. Dependent variable: volume of gas produced.
(d) M1 change in volume = 32 - 0 = 32 cm³
(d) M1 rate = change in volume / change in time = 32 / 20
(d) A1 1.6 cm³/s cao
(d) Answer: 1.6 cm³/s
(e) M1 (50 - 48) / (60 - 40)
(e) A1 0.1 cm³/s cao
(e) B1 the reaction is almost finished / has slowed down greatly, as very little gas is being produced oe
(e) Answer: 0.1 cm³/s; the reaction is almost over.
(f) B1 50 s (accept 50-60 s) cao
(f) B1 the volume of gas stays constant (at 50 cm³) and does not increase further oe
(f) Answer: By about 50 s; the volume stops increasing (stays at 50 cm³).
(g) B1 use a gas syringe with smaller graduations (finer resolution), or read at eye level oe
(g) B1 explanation linked to the suggestion, e.g. smaller graduations reduce the uncertainty in each reading oe
(g) Answer: Use a gas syringe with a finer scale (smaller graduations); this reduces the uncertainty in each volume reading.
(h) B1 hazard: hydrogen gas is flammable, or dilute hydrochloric acid is an irritant/can harm skin and eyes
(h) B1 matching control measure: keep away from naked flames, or wear eye protection/gloves
(h) Answer: Hazard: hydrogen gas is flammable. Control: keep away from naked flames.
(i) B1 same length/mass of magnesium ribbon each time
(i) B1 any other valid control, e.g. same total volume of acid, same temperature, same apparatus
(i) Answer: Any two of: same length/mass of magnesium ribbon, same volume of acid, same temperature, same apparatus.
(j) M1 (48 - 32) / 32 x 100
(j) A1 50% cao
(j) Answer: 50%

Question 11

M1 density = mass / volume
M1 47.6 / 18.0
A1 2.64 g/cm³ (3 s.f.) awrt
Answer: 2.64 g/cm³

Question 12

(a) M1 (84.2 + 84.5 + 84.1 + 84.6 + 84.3) / 5
(a) A1 84.34 cm (accept 84.3 cm) awrt
(a) Answer: 84.34 cm
(b) M1 84.6 - 84.1
(b) A1 0.5 cm cao
(b) Answer: 0.5 cm

Question 13

(a) B1 directly proportional (linear, through the origin) oe
(a) Answer: Directly proportional.
(b) M1 0.8 x 7.5
(b) A1 6.0 cm cao
(b) Answer: 6.0 cm

Question 14

M1 gradient = (30 - 6) / (20 - 0)
A1 1.2 cao
B1 rate of reaction at t = 10 s = 1.2 cm³/s (correct unit stated) ft
Answer: 1.2 cm³/s

Question 15

M1 uncertainty = 1 / 2 = 0.5 degC
M1 percentage uncertainty = (0.5 / 25) x 100
A1 2% (nearest whole per cent) awrt
Answer: 2%

Question 16

(a) B1 systematic error (zero error) oe
(a) Answer: Systematic error (a zero error).
(b) B1 every reading would be 0.5 g too high oe
(b) B1 because it is a systematic error, it affects every measurement in the same way and by the same amount oe
(b) Answer: Every mass measured would be 0.5 g too high, since the zero error shifts all readings by the same fixed amount.

Question 17

B1 50 cm³ cao
B1 the graph has already levelled off (plateaued) from t = 50 s onward, showing no more gas is being produced
B1 the magnesium (the limiting reactant) has been completely used up, so the reaction has stopped and no further hydrogen can be produced oe
Answer: 50 cm³

Question 18

B1 a mean reduces the effect of any anomalous or randomly varying result oe
B1 gives a more representative/reliable value at each concentration, allowing a fairer comparison and a more valid conclusion oe
Answer: A mean from repeats smooths out random variation and anomalies, giving a more reliable value to compare between concentrations, so the conclusion is more valid.

Question 19

Level 0 (0): No relevant content, or the answer does not address planning an investigation.
Level 1 (1-2): A basic method is given. The independent and/or dependent variable may be named, but there is little or no reference to controlling other variables, apparatus, or improving reliability.
Level 2 (3-4): A clear method is given describing suitable apparatus and key steps. Some relevant variables to control are stated and/or repeats are mentioned, but detail is incomplete or not fully linked together.
Level 3 (5-6): A detailed, logically ordered method is given. It states a suitable range of concentrations, clearly controlled variables, an appropriate method for measuring the dependent variable, and explains how repeats and means will be used to improve reliability. Relevant safety precautions are included.
Indicative content:
- Use a fixed length or mass of magnesium ribbon for every test, e.g. 3 cm each time.
- Use the same volume of acid each time, e.g. 50 cm^3.
- Vary the concentration of the acid across a range of values, e.g. by diluting a stock acid to give concentrations such as 2.0, 1.5, 1.0 and 0.5 mol/dm^3.
- Keep the temperature the same for every test, e.g. by working at room temperature or using a water bath.
- Measure the volume of gas produced using a gas syringe connected to the reaction flask.
- Start a stopwatch as soon as the magnesium is added to the acid.
- Record the volume of gas at regular time intervals, e.g. every 10 seconds, or record the time taken to collect a fixed volume of gas.
- Repeat each concentration at least three times and calculate a mean.
- Identify and exclude any anomalous results before averaging.
- Wear eye protection and keep hydrogen gas away from naked flames.
- Plot a graph of rate (or time taken) against concentration to identify the pattern.

Question 20

Level 0 (0): No relevant content, or the answer does not evaluate the method.
Level 1 (1-2): A simple weakness or improvement is identified with little or no explanation, e.g. 'he should repeat it'.
Level 2 (3-4): More than one weakness in the method is identified (e.g. the anomalous result, the resolution of the gas syringe, timing errors), with some explanation of the effect on the results.
Level 3 (5-6): A well-reasoned evaluation covering both reliability (repeats, anomalies, means) and accuracy (equipment resolution, reaction-time errors, gas leaks) is given, with clearly justified and specific improvements linked to each weakness identified.
Indicative content:
- Only one time point (t = 30 s) was repeated and had an anomaly identified and excluded; repeating readings at every time interval would improve reliability.
- A gas syringe with smaller graduations (finer resolution) would reduce the uncertainty in each volume reading, improving accuracy.
- There may be a delay between adding the magnesium and starting the stopwatch, or in fitting the bung; this reaction-time error would make early readings inaccurate. Practising the timing or using an automatic trigger would reduce this.
- Gas may escape before the bung is fully sealed, making recorded volumes lower than the true volume; checking the seal or using a delivery tube would reduce this loss.
- Temperature was not controlled or monitored during the reaction; keeping it constant, e.g. using a water bath, would make repeats and comparisons fairer.
- Using the mean of repeated readings at every time interval, not just at t = 30 s, would give more reliable data across the whole graph.

Working Scientifically - Worksheets, Questions and Revision

Next in this strand

CE.S-W1 Working Scientifically

Question 1

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Question 11

Question 12

Question 13

Question 14

Question 15

Question 16

Question 17

Question 18

Question 19

Question 20

Question 1

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Question 11

Question 12

Question 13

Question 14

Question 15

Question 16

Question 17

Question 18

Question 19

Question 20