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Measurements of Time, Temperature, Mass and Volume

Choose and use apparatus for time, temperature, mass and volume, including correct scale readings, units, meniscus technique and precision.

  • SEC G3 Pure Chemistry 2027
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Learning objectives

  • name appropriate apparatus for the measurement of time, temperature, mass and volume; including burettes, pipettes, measuring cylinders and gas syringes
  • make and record observations, measurements and estimates;

Chemistry results are useful only when another person can understand and repeat the measurements. Choose suitable apparatus, record the value with justified precision and always include its unit.

1. Definition

Measurement is the process of assigning a numerical value and unit to a quantity (e.g., time, temperature, mass, volume) using an appropriate instrument.

2. Key Ideas

  • In school chemistry, common units are second (s), degree Celsius (°C), gram (g), cm³ and dm³.
  • Choose the instrument based on the required resolution (the smallest readable change), the required accuracy, and the job (fixed volume vs variable volume).
  • Precision describes how close repeated readings are to one another; it is not the same as resolution.
  • Record readings to the correct decimal places and include units.
  • Reduce errors: read scales at eye level to avoid parallax error, and read the correct part of the meniscus.

3. Detailed Explanations

Quick Recall (before you start)
  • 1 cm³ = 1 mL and 1 dm³ = 1 L = 1000 cm³.
  • Parallax error = reading the scale from above/below eye level.
  • Meniscus = curved liquid surface; for water, read the bottom of the curve.

A. Measurement of Time

  • SI unit: second (s).
  • Common instrument: stopwatch.
Exam Trap: Resolution is not the same as uncertainty

A stopwatch may display 0.01 s (its resolution), but a hand-timed result has additional uncertainty due to human reaction time. Repeat readings and calculate a mean when appropriate.

B. Measurement of Temperature

  • Record laboratory temperature in degrees Celsius (°C) unless the question specifies another unit.

  • Instruments: laboratory thermometer, digital thermometer, data logger (temperature sensor + automatic recording).

  • Good practice: ensure the bulb/sensor is fully in the substance and not touching the container wall; wait for the reading to stabilise.

Laboratory Warning

Mercury is toxic if a thermometer breaks and mercury is released. Do not touch the spill; move away and tell your teacher immediately so the school’s spill procedure can be followed.

C. Measurement of Mass

  • SI unit: kilogram (kg). In school labs, mass is usually recorded in gram (g).
  • Instruments: beam balance (rare) and electronic balance.
Using an electronic laboratory balanceTwo panels show an empty weighing boat on an electronic balance being tared to zero, followed by solid being added until the display reads 2.50 grams.1. Tare the container0.00 gTARE / ZEROEmpty container included, then zeroed2. Add the substance2.50 gDisplay gives the substance mass
Tare the empty container first, then add the substance until the display shows the required mass.
  • When measuring a substance directly in a container, tare (zero) the balance with the empty container before adding the substance. In a weigh-by-difference method, record the required masses instead of taring between readings.

D. Measurement of Volume (Liquids)

  • SI unit: cubic metre (m³). In chemistry you commonly use cm³ and dm³ (L).
  • Key conversions:
    • 1 cm³ = 1 mL
    • 1 dm³ = 1 L = 1000 cm³
    • 1000 L = 1 m³

The apparatus you choose depends on whether you need an approximate volume or a precise volume.

ApparatusWhat it is used forTypical precision (school lab)
BeakerHolding/mixing; rough volumes onlyVery low (do not use for “exactly …” questions)
Measuring cylinderMeasuring a variable volume when high precision is not requiredOften to the nearest 0.5 cm³ or 1.0 cm³ (depends on size)
PipetteMeasuring a fixed volume accurately (e.g., 25.0 cm³)High (used for titration/standard solutions)
BuretteDelivering a variable volume accurately (titration)Read to the nearest 0.05 cm³ and record two decimal places (e.g., 24.00, 24.05)
Volumetric flaskMaking a solution up to an exact final volume (standard solution prep)High (use the calibration mark)

Mini-example (common exam wording):

  • “Exactly 25.0 cm³” → pipette.
  • “About 25 cm³” → measuring cylinder.

For measuring the volume of gases, see Collection of Gases and Measurement of their Volumes.

Laboratory Warning

Never pipette by mouth. Use a pipette filler.

E. Meniscus and Parallax Error

When a liquid is in a narrow container (measuring cylinder, burette, pipette), the surface is usually curved. This curved surface is the meniscus.

  • Concave meniscus (e.g., water): read the bottom of the curve.
  • Convex meniscus (e.g., mercury): read the top of the curve.
  • Read at eye level to avoid parallax error (apparent shift in reading when viewed from above/below the scale).
Correct and incorrect viewing positions for a concave meniscusThe correct panel shows an eye level with the bottom of a concave meniscus and a horizontal sight line. The parallax panel shows eyes above and below the meniscus with diagonal sight lines, which shift the apparent reading.Correct: eye levelRead the lowest point of the curve.Wrong: parallaxThe apparent scale position shifts.
Read the bottom of a concave aqueous meniscus with your eye level with the liquid surface. A view from above or below causes parallax error.

4. Common Mistakes

  • Writing “accurate to 0.01” when you mean the resolution is 0.01.
  • Forgetting to tare the balance before measuring mass in a container.
  • Reading the meniscus from above/below eye level (parallax).
  • Recording a burette reading to 1 decimal place, or using a final digit other than 0 or 5 for the nearest-0.05 cm³ reading.
  • Using a measuring cylinder or beaker when the question says “exactly 25.0 cm³”.

5. Exam Tips

Describe the technique precisely

If the question is about technique, you usually need to say “read at eye level to avoid parallax error” and “read the bottom of the meniscus (for water)”.

Instrument choice is predictable

“Exactly 25.0 cm³” usually points to a pipette. “Variable volume delivered” points to a burette. “Make up to a fixed final volume” points to a volumetric flask.

6. Worked Examples

Modelled example 1

Choosing the Right Apparatus (Fixed Volume)

Core

Problem

Which apparatus is most suitable for measuring exactly 25.0 cm³ of dilute acid for a titration: a 50 cm³ beaker, a 50 cm³ measuring cylinder or a 25.0 cm³ pipette?
Study the worked solution

  1. Read the measurement requirement

    Method

    Identify that the task needs one exact fixed volume.

    Reason

    The word “exactly” rules out apparatus intended for rough or lower-precision estimates.

    Working

    Required: fixed 25.0 cm³ aliquot.

  2. Match the apparatus

    Method

    Select the 25.0 cm³ pipette.

    Reason

    A volumetric pipette is calibrated to deliver that fixed volume accurately; a beaker or measuring cylinder is not suitable for the stated precision.

    Working

    Answer: 25.0 cm³ pipette.

Guided practice 2

Recording a Burette Reading

About 4 min

Problem

A burette scale indicates exactly 24.0 cm³ at the marked tenth. Which recorded value communicates the correct precision: 24, 24.0, 24.00 or 24.000 cm³?

Choose the justified number of decimal places

Recorded burette value

Hints

Hint 1: instrument rule
Recall the recording convention for a standard burette.
Hint 2: precision
Too few decimal places loses readable precision; too many claims precision the scale cannot support.
View solution step by step

  1. Apply the burette convention

    Method

    Record the reading to two decimal places.

    Reason

    A standard burette scale supports the second decimal place through estimation between graduations.

    Working

    24.00 cm³.

  2. Reject false alternatives

    Method

    Reject both coarser and unjustifiably finer recordings.

    Reason

    24 and 24.0 discard precision, while 24.000 implies resolution the apparatus does not provide.

    Working

    Correct recording: 24.00 cm³.

Common misconception 3

Taring a Balance

Find and correct the mistake

Learner method

A student places a weighing boat beside the balance, adds sodium chloride to it, then puts both on the balance and stops when the display reads 2.50 g. Correct the direct-measurement method.

Remove the container mass from the reading

First action
Final display

View solution step by step

  1. Zero with the container

    Method

    Place the empty weighing boat on the balance and press tare/zero.

    Reason

    This subtracts the container contribution from subsequent readings.

    Working

    Empty boat on pan; display set to 0.00 g.

  2. Add the required solid

    Method

    Add sodium chloride until the display reads 2.50 g.

    Reason

    After taring, the displayed increase is the solid’s mass alone.

    Working

    Measured sodium chloride mass: 2.50 g.

Examiner practice 4

Measure a temperature change

3 marks

Examination question

A student mixes two solutions and wants to measure the greatest temperature rise. Name suitable apparatus and describe how to obtain the temperature change. [3 marks]

Choose apparatus and state both readings

View solution step by step

  1. Choose suitable apparatus

    1 mark

    Method

    Use a laboratory thermometer or temperature probe.

    Reason

    Either instrument measures the changing temperature directly.

    Working

    Place the bulb or probe in the reaction mixture without touching the container.

  2. Record the relevant temperatures

    1 mark

    Method

    Record the initial temperature, then the highest temperature reached after mixing.

    Reason

    The question asks for the greatest rise, so the maximum reading is needed.

    Working

    Record both values in °C to the instrument’s resolution.

  3. Calculate the change

    1 mark

    Method

    Subtract the initial temperature from the maximum temperature.

    Reason

    A rise is final/maximum minus initial.

    Working

    Δ T = Tₘₐₓᵢₘᵤₘ-Tᵢₙᵢₜᵢₐₗ.

Challenge 5

Anomalous Result (Time)

Minimal support

Repeated-data transfer

A reaction mixture turns cloudy after 18.2 s, 18.5 s and 31.0 s in three trials. Use the data to calculate a justified mean time.

Select the consistent trials before averaging

Result to exclude
Mean of consistent results

Hints

Hint 1: consistency
Find the two readings that agree closely before calculating.
Hint 2: rounding
Average only that consistent pair, then match the precision of the time readings.
View solution step by step

  1. Identify the anomaly

    Method

    Exclude 31.0 s from this mean.

    Reason

    It is far from the mutually consistent 18.2 s and 18.5 s readings.

    Working

    Consistent set: 18.2 s and 18.5 s.

  2. Calculate and report

    Method

    Average the consistent pair and round appropriately.

    Reason

    The mean should not claim finer precision than the original readings.

    Working

    (18.2 + 18.5)/2 = 18.35 s ≈ 18.4 s.

7. Mind Stretchers

Mind stretcher 1: Error Analysis (Meniscus + Parallax)Extension

Question: Two students read the same measuring cylinder containing water.

  • Student A reads from above the liquid level and records 36.0 cm³.
  • Student B reads at eye level and records 34.0 cm³.

Who is more likely to be correct, and why?

Show Answer

Answer: Student B.

Reason: The correct technique is to read the bottom of the concave meniscus at eye level. Reading from above causes parallax error, so Student A’s value is not reliable.

Mind stretcher 2: Instrument Choice (Making a Standard Solution)Extension

Question: You need to prepare exactly 250.0 cm³ of sodium hydroxide solution. Which apparatus must be used to make the solution up to the correct final volume?

Show Answer

Answer: A 250 cm³ volumetric flask.

Reason: A volumetric flask is calibrated to contain an exact final volume when the bottom of the meniscus is on the calibration mark.

8. Quiz

Quiz Time!

Practise apparatus choice, units, meniscus readings, resolution and measurement errors.

Start measurement quiz