OIL AND WATER – Part 1
Description of activity
Students investigate the problem ‘How do the characteristics of water affect the way oil mixes with it?’
The suggested time for this activity is approximately 1 hour.
Students have investigated the way in which different substances mix or act with water, eg dissolving (soluble) and non-dissolving (insoluble) substances, or floating and sinking. They may be presented with news items or stories about oil slicks or oil leaks in water.
Knowledge and understanding
- Glass or clear plastic containers, spoons, sponges
- Water supply, salt, ice, detergent, simulated oil made from a mixture of vegetable oil and cocoa powder
- Template of a table for recording data
Work, health and safety
- Check relevant Work, health and safety guidelines.
- Highlight to students the need to be responsible and safe when using water.
- Be mindful of water spillage and slippery floors.
Evidence of work for assessment purposes
- A record of results comprising a table and pictures
- A statement summarising the results of the investigation
STEM teaching and learning activities
- Students are shown the simulated oil explaining that this represented oil that leaked from a boat.
- Students pour the oil into water and observe what happens. Students record their observations.
- Pose the question ‘If a boat leaks oil, would there be any differences if the boat was on the sea or in a lake, in the tropics or Antarctica?’
- Discuss with students the different environmental features in these locations.
- Students discuss what these differences would mean, eg salt vs fresh water, warmer water vs icy water.
- Students discuss how they would simulate these different conditions.
- Students research, discuss and record different methods of cleaning up oil spills in water.
- Students design a method to clean an oil spill that they have made. They must use the same method for salt water and fresh water, icy water and warm water.
- In order to do this, students must determine:
- the amount of water to be used (the same amount for each test)
- the amount of simulated oil to be used (the same amount for each test)
- what types of materials they will use
- how much of each material they will need to deal with the amount of oil.
- Students carry out their planned activity and record their results in a table, eg
- Students record a statement which outlines their answer to the problem posed.
Data – information collected through observations and measurements that can be used to draw conclusions
Dissolve – to mix with a liquid and become a part of that liquid
Experiment – a scientific test in which you perform a series of actions and carefully observe their effects in order to learn about something
Float – to rest or move on or near the surface of a liquid
Results – information gained from an investigation
Sink – to go down below the surface of a liquid
Surface – the outermost layer of an object
Table – a set of facts or figures displayed in columns and rows
Change only one factor at a time
When testing ideas, it is important that students realise that only one factor can be changed at a time. If more than one factor is changed and a change is observed, it is unclear which factor caused the change. In this case the effect of salt water vs fresh water would be tested in a separate experiment to the effect of warmer water vs icy water.
The following outlines some common preconceived ideas that many students hold, which are scientifically inaccurate and may impede student understanding.
When salt dissolves in water, it disappears
When salt is placed in water, we may not be able to see it, but it does not disappear. The salt is still in the water. The salt can be tasted and if the water is evaporated the salt remains.
If you can’t see a change, the experiment didn’t work
Results that show ‘no change’ do not mean that the experiment did not work. It means that the factors that were changed do not affect the factor being measured. This may still be a valid result.
If you can’t see a change, nothing happened
Seeing is not the only way of observing. Students can use all their senses (although we don’t tend to use taste) to observe. Sometimes we need specialised equipment to detect changes.
Adjustments for the diversity of learners
Collect some feathers and dip them into the simulated oil. Describe the effect of the oil on the feather. This leads into discussion about the effect of oil spills on wildlife.
Students may split the investigations so that different groups carry out different investigations and share results.
Some students may combine characteristics, eg cold, fresh water vs cold, salty water and warm, fresh water vs warm, salty water. Some students research to find locations that would have these environmental features.
In this STEM activity your students developed the skills of hypothesising, planning, designing and constructing, and carrying out an investigation and collecting and displaying and analysing data to draw logical scientific conclusions. All these skills encompass the Working Scientifically and Working Technologically processes further developed through Stages 4 to 6 in the science and technology courses.