Materials — OCR GCSE Physics
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Materials explained
This practical apparatus criterion asks you to choose the right instrument for each quantity and to record readings accurately.
Read the full explanation
Length is measured with a ruler or vernier calliper, choosing the scale that gives suitable resolution. Area is found by measuring lengths and calculating, for example length × width for a rectangle. Mass is measured with a balance, zeroed before use. Time is measured with a stopwatch, often timing several repeats to reduce random error. Volume of a liquid is read from a measuring cylinder at eye level, taking the bottom of the meniscus; volume of a regular solid is calculated from its dimensions. Temperature is measured with a thermometer or digital probe, allowing it to settle. A multiple-choice question tests whether you can match instrument to quantity and record with correct units and precision.
Use of such measurements to determine densities of solid and liquid objects.
Density tells you how much mass is packed into each cubic centimetre or cubic metre of a material, and you find it by dividing mass by volume. For a regularly shaped solid, measure length, width and height with a ruler and multiply them to get volume in cm³, then read mass on a balance in grams and divide. For an irregular solid, use a displacement method: record the water level in a measuring cylinder, lower the object in fully, and take the rise in level as the object's volume. For a liquid, pour a measured volume into a measuring cylinder and find the mass of that volume, subtracting the mass of the empty container. Keep units consistent, for example g and cm³ give g/cm³, and convert to kg/m³ by multiplying by 1000.
Your focus
- Select appropriate apparatus for measuring length, area, mass, time, volume and temperature.
- Record measurements accurately with correct units and suitable precision.
- Describe how to reduce error when taking and recording measurements.
Show all 6 objectives
- Calculate the density of a solid or liquid from measured mass and volume.
- Select a suitable method to measure the volume of a regular or an irregular object.
- Convert a density value between g/cm³ and kg/m³.
Materials exam tips
Marking Points
- Selects a ruler, vernier calliper or micrometer for length according to the resolution needed.
- Calculates area from measured lengths rather than guessing, for example length × width for a rectangle.
- Chooses a balance for mass and zeroes it before taking the reading.
- Uses a stopwatch for time and repeats readings to reduce random error.
- Reads a measuring cylinder at eye level, taking the bottom of the meniscus, and records volume in cm³ or ml.
- Selects a thermometer or digital temperature probe and waits for the reading to settle before recording.
- Divides mass by volume to calculate density and states the unit as g/cm³ or kg/m³.
- Reads volume of a regular solid by multiplying measured length, width and height.
- Finds volume of an irregular solid from the rise in water level when it is fully submerged.
- Subtracts the mass of the empty container when finding the mass of a liquid sample.
- Converts between g/cm³ and kg/m³ correctly by multiplying or dividing by 1000.
Examiner Tips
- 💡Match the instrument to the quantity before looking at the options.
- 💡Check that each recorded value carries the correct unit.
- 💡Consider resolution: choose the instrument that can measure the smallest change required.
- 💡Remember that area and the volume of a regular solid are calculated from measured lengths.
- 💡Write the equation density = mass ÷ volume before substituting numbers so units stay clear.
- 💡Show the volume calculation separately for irregular solids, stating the starting and final water levels.
- 💡Check whether the answer needs g/cm³ or kg/m³ and convert with a factor of 1000 if required.
Common Mistakes
- Reads a measuring cylinder from above or below eye level; correct this by reading at eye level at the bottom of the meniscus.
- Records a measurement without a unit; correct this by always stating the unit, such as cm, g, s, cm³ or °C.
- Uses a ruler to measure mass or a balance to measure volume; correct this by matching each instrument to the quantity it measures.
- Takes a single timing and treats it as exact; correct this by repeating and averaging to reduce random error.
- Adds length, width and height instead of multiplying them; multiply the three dimensions to obtain volume.
- Forgets to subtract the mass of the empty measuring cylinder; subtract the container mass to isolate the liquid.
- Mixes grams with cubic metres without converting; keep mass and volume in matching units before dividing.