New
New
Year 10
AQA
Higher

Uncertainties in measurements: chemistry

I can explain why there is some uncertainty when measurements are made, how to minimise uncertainty, and calculate uncertainties.

New
New
Year 10
AQA
Higher

Uncertainties in measurements: chemistry

I can explain why there is some uncertainty when measurements are made, how to minimise uncertainty, and calculate uncertainties.

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Lesson details

Key learning points

  1. Whenever a measurement is made, there is always some uncertainty about the result obtained.
  2. The uncertainty of an individual measurement is equal to half the resolution of the device used to take the measurement.
  3. The higher the resolution, the lower the uncertainty of an individual measurement.
  4. Half the range of repeated measurements equals the uncertainty of a mean value.
  5. The uncertainty of a measurement provides a range within which the actual value can be found.

Common misconception

Pupils rarely consider the choice of equipment and its link to the accuracy of the data they collect in a practical.

Highlight that equipment with smaller resolution provides more precise measurements, which can decrease the uncertainty of a calculated mean.

Keywords

  • Uncertainty - is the range of measurements within which the true value can be expected to be found. On apparatus, it is half the value of one resolution marking.

  • Measurement - provides quantitative information about an object or system.

  • Mean - is an average calculated by adding up the values of a set of measurements and dividing by the number of measurements in the set.

  • Resolution - is the smallest change a piece of apparatus can measure - shown by its markings.

  • Apparatus - a piece of equipment that is designed for a particular use.

Challenge pupils to find the uncertainty for the same measurement using apparatus of varying resolution. Discuss the pros/cons of apparatus with varying resolution and its affect of investigation results.
Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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6 Questions

Q1.
Which piece(s) of laboratory equipment are typically used for measuring volume?
Correct answer: Graduated cylinder (measuring cylinder)
Balance
Correct answer: Pipette
Ruler
Q2.
Which mathematical operation(s) would you use to calculate the average of three measurements?
Correct answer: Addition
Subtraction
Multiplication
Correct answer: Division
Q3.
In an experiment, what type of variable is the one that the scientist changes?
Correct answer: Independent variable
Dependent variable
Control variable
Uncontrolled variable
Q4.
In an experiment measuring the effect of sunlight on plant growth, what is the dependent variable?
The type of plant.
The amount of water given to each plant.
Correct answer: The height of the plant.
The amount of sunlight each plant receives.
Q5.
Significant refer to the digits in a measurement that are known with certainty plus the first digit that is uncertain.
Correct Answer: figures
Q6.
Match the following terms with their correct definitions:
Correct Answer:Random Error,An error that has an equal probability of being too high or too low.

An error that has an equal probability of being too high or too low.

Correct Answer:Precision,The closeness of two or more measurements to each other.

The closeness of two or more measurements to each other.

Correct Answer:Accuracy,The degree to which a measurement reflects the true value.

The degree to which a measurement reflects the true value.

Correct Answer:Control Variable,A variable that is kept constant throughout an experiment.

A variable that is kept constant throughout an experiment.

6 Questions

Q1.
What does the uncertainty of a measurement indicate?
The exact value of the measurement.
The precision of the apparatus.
Correct answer: The range within which the true value can be found.
The number of measurements taken.
Q2.
Match the term to its correct definition.
Correct Answer:Measurement,Quantitative information about an object or system.

Quantitative information about an object or system.

Correct Answer:Uncertainty,The range within which the true value can be found.

The range within which the true value can be found.

Correct Answer:Mean,An average calculated from a set of values.

An average calculated from a set of values.

Correct Answer:Resolution,The smallest change a piece of apparatus can measure.

The smallest change a piece of apparatus can measure.

Correct Answer:Apparatus,A piece of equipment designed for a particular use.

A piece of equipment designed for a particular use.

Q3.
How does a higher resolution affect the uncertainty of a measurement?
Increases the uncertainty.
Correct answer: Decreases the uncertainty.
Has no effect on uncertainty.
Makes the measurement less accurate.
Q4.
is the range of measurements within which the true value can be expected to be found. It reflects the limitations of our measuring devices.
Correct Answer: uncertainty
Q5.
The resolution of a measuring device is 0.02 g. What is the uncertainty of an individual measurement?
Correct answer: 0.01 g
0.02 g
0.04 g
0.1 g
Q6.
Why is it important to consider the choice of equipment when conducting measurements?
Equipment choice has no impact on the outcome.
Correct answer: Different equipment can yield different levels of precision.
Better equipment always guarantees the correct value.
Equipment choice affects the colour of the data.