Rice Race
Teacher Notes
Aims and Overview
Using grains of rice, pupils investigate the viscosity (thickness) of 3 different liquids. Pupils work in
small groups to time how long a grain of rice takes to fall through the liquid and then carefully record
the results.
The experiment will be repeated a total of three times to ensure fair testing and reliable results.
The experiment aims to:
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Introduce the concept of viscosity (thickness) of liquids
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Enable pupils to use scientific equipment including measuring cylinders and stopwatches
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Use averages to improve the accuracy of the experimental results
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Introduce the concept of reliability
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Develop pupil’s group work skills in preparing, completing and discussing the results from
the experiment.
This experiment uses readily available consumables in addition to the equipment supplied.
Curriculum Links and Skills
Communication: Oracy, reading, writing and wider communication via class discussion and
completion of the hand out using scientific vocabulary and terms.
Enquiry: Identifying different viscosities (thicknesses of liquids) and carrying out fair testing.
Developing: Using apparatus and equipment safely to collect reliable data.
Developing: Pupils follow the planned approach/method, revise it where necessary, taking action to
control the risks to themselves and others.
Developing: Identify, describe and explain trends, patterns and relationships.
Science: Communicating ideas, information and data through class discussion and recording of
experiment results in a table using relevant scientific vocabulary.
Knowledge and Understanding: Evaluation of the information gathered and discussion of the real
world applications of scientific experiments.
Reflecting: Justifying any improvements made to the planning approach/method.
Equipment
Each group of pupils will require:
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3 different concentrations of washing up liquid, labelled A, B and C (see preparation notes)
1 measuring cylinder (100ml)
1 plastic forceps
15 rice grains (this does not need to be counted out precisely)
1 stopwatch
Pupil worksheet and method
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Rice Race
Teacher Notes
Lab Notes and Safety Information
Please read the accompanying risk assessment before starting the experiment. The risk assessment
covers the equipment and resources supplied – please risk assess the venue and any additional
equipment / resources used yourself.
The activity is low risk and eye protection is not required. The experiment uses only household items,
however those with sensitive skin should be extra careful not to touch the washing up liquids to avoid
allergic reactions / skin irritations. Pupils should be advised not to eat any of the substances used and
to wash their hands after the experiment.
Pupils should be warned that the measuring cylinders need to be placed on an uncluttered surface
away from the table edge. They will need to be made to understand that spillages can occur and that
they should report these straightaway. They should not try to clear up large spillages themselves.
If substances are ingested or come into contact with the eye, seek medical advice immediately.
Preparation Notes
The 3 liquids are as follows:
Liquid A = 50% washing up liquid & 50% water
Liquid B = 25% washing up liquid & 75% water
Liquid C = 100% water
The rice grains may float if placed on the surface so it is a good idea to slightly “overfill” the cylinders
above the 100ml mark and to introduce the grains below the surface using the forceps.
There is the potential for the activity to become a little messy so good supervision is required.
It is important that the pupils know how to read the measuring cylinder correctly – it is best to bend
down and have your eyes level with the mark you are looking at.
Care should be taken to ensure pupils are confident and competent in operating and resetting
stopwatches – they may need to practise first.
Method
Please refer to pupil hand-out for the method, which includes pictures of each step.
Results
Results will be recorded by the pupils on the hand-out provided. Pupils may need assistance with
calculating the average (mean) time for rice to pass through each liquid.
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Rice Race
Teacher Notes
Key Questions
These are questions to be answered by pupils either during class discussions or as a written task. Full
answers are shown as an example of what will be expected at key Stage 3.
Why do the grains of rice fall through the liquid?
They sink as they are heavier (more dense) than the liquid and the force of gravity pulls them down.
The rice grains push the washing up liquid out of the way as they fall through.
What happens in the different liquids?
The grains fall faster in some liquids and slower in others.
Are the liquids all the same?
No, the liquids are not the same. Some liquids are thicker or more viscous. The more viscous liquids
slow down the grains the most. You can also see the liquids are different from their colour.
Why do you think the rice falls slower in some liquids compared with others?
It is harder for the rice to travel through the more viscous, more gloopy liquids. Less viscous liquids
allow the rice grains to pass through quicker.
Think about swimming in syrup rather than a pool of water, it would take you longer to reach the other
side!
Extension Activities
These are additional questions or activities that can be given to pupils who finish quickly or who are
more able and talented.
What would happen if you tried this experiment with other objects such as small pasta shapes or
small pebbles?
If the objects are heavier, they should sink faster. However, if an object is lighter than a grain of rice, it
should travel slower.
Find the time it takes for rice to travel through 100% washing up liquid. What does this tell you
about the original three liquids?
The time to travel through pure washing up liquid is longer than the original tests. Therefore the original
three liquids must all be less viscous than pure washing up liquid. They were a mixture of washing up
liquid with water.
Would you get the same results if you used different liquids? What other liquid could you use?
The results would be different depending on the liquid used. For example oil is thinner or less viscous
than washing up liquid so a grain of rice would fall/travel faster. However, a liquid like bubble bath is
very thick and viscous so the grains of rice would travel much slower. You could try any safe liquid you
have in school – milk, cooking oil, juice etc.
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Rice Race
Teacher Notes
Vocabulary
Viscosity
A term to describe liquids. It is similar to describing its thickness / how gloopy it is. High viscosity
means a liquid will not flow easily or quickly and objects will take a longer time to pass through it. For
example, treacle has a much higher viscosity than water.
Fair Test
It is important for an experiment to be a fair test. To be a fair test, you only change one thing. For
example the liquid, and keep everything else the same, such as always using rice.
Reliability
The experiment is repeated to make sure the results are reliable. The second and third reading from the
stopwatch should be similar to the first – this tells us the information can be trusted and is reliable. If
the readings are very different, our experiment is not set up well and we should repeat the tests more
times to collect more reliable results.
Average
A way of calculating the middle of a set of numbers, to help remove extremely high and low values.
Measuring Cylinder
A common piece of scientific equipment used in laboratories to measure the volume of a liquid.
Stopwatch
A common piece of equipment used to measure exact times, for example in a race.
Conclusion Notes
The rice grains should travel more slowly through the more viscous liquids, with higher washing up
liquid concentration, more slowly than the less viscous liquids with higher water content. This is
because the more viscous the liquid, the more time it takes for the liquid to move out of the way of
the rice grains.
The repetition of the experiment and calculation of averages leads nicely to a discussion on experiment
reliability.
For more information and further resources please visit our website: www.tqg.org.uk
Techniquest Glyndŵr is a registered charity: charity number 1102959
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