On February 28th 2023 5th/6th class travelled to the RDS to present their project 'Do oil and water ever mix?'. The children had a great day out and were delighted by the positive feedback they received from the judge, Colm O'Callaghan (see below). As well as getting the chance to look at the projects of other schools, there was a range of interesting stands to explore, and plenty of freebies to gather up!
'A truly inspiring project informed by the curious minds of the students. Your approach to research and enquiry was clever, well-considered and thoughtful. It is evident that everyone played an active part in the study and there was great collaboration between you all. You brilliantly demonstrated your scientific approach - controlling certain parts while changing certain variables. This led you to opening up the project to further expansion and development. The presentation of the results was excellent - informed, clear and articulate. The joy and enthusiasm in your oral presentation demonstrated how much you gained from the project . Well done.'
'A truly inspiring project informed by the curious minds of the students. Your approach to research and enquiry was clever, well-considered and thoughtful. It is evident that everyone played an active part in the study and there was great collaboration between you all. You brilliantly demonstrated your scientific approach - controlling certain parts while changing certain variables. This led you to opening up the project to further expansion and development. The presentation of the results was excellent - informed, clear and articulate. The joy and enthusiasm in your oral presentation demonstrated how much you gained from the project . Well done.'
Do oil and water ever mix?
Our research
https://wonderopolis.org/wonder/why-dont-oil-and-water-mix
https://mocomi.com/why-oil-and-water-dont-mix/
https://www.youtube.com/watch?v=mPob0pVvVzg
https://www.youtube.com/watch?v=h5yIJXdItgo
https://www.youtube.com/watch?v=vSXTBnnx4OA
Our experiment
The control - oil and water.
Aim: To demonstrate that oil and water do not usually mix.
Part 1:
Whisking
Aim: To see if whisking oil and water causes them to mix together.
Whisking oil and water together causes them to mix, but only temporarily. It breaks the oil and water molecules apart and mixes them up amongst each other, but there are no bonds formed, and so they separate once again the whisking stops.
Whisking would help the oil molecules to be completely coated if adding an emulsifier, so can be useful in creating an emulsion when another substance is added.
Washing-up liquid
Aim: To see if adding washing-up liquid to oil and water causes them to mix together.
Washing-up liquid helps water and oil to mix. From our research we know that this is because washing up liquid is a surfactant. As well as bonding to both the oil and the water, a surfactant helps reduce the surface tension of water. Surface tension is the force which helps a blob of water on a surface hold its shape and not spread out. Washing up liquid helps break apart these forces.
Source: https://www.york.ac.uk/res/sots/activities/soapysci.htm
Mustard
Aim: To see if adding mustard to oil and water causes them to mix together.
Mustard was the best substance we tested for mixing the oil and water together. From our research we know it is an emulsifier because mustard seeds contain a sticky substance called mucilage, that coats oily particles and allows them then to bond with water molecules.
Source: https://www.ochef.com/why-is-mustard-a-good-emulsifier
Egg yolk
Aim: To see if adding egg yolk to oil and water causes them to mix together.
Egg yolk helps oil and water mix. We know from our research that it is an emulsifier because it contains lecithin. The albumin protein in egg white also make it an emulsifier. Eggs are widely used in cooking because of their emulsifying properties.
Source: https://homekitchentalk.com/is-egg-an-emulsifier/
Vinegar
Aim: To see if adding vinegar to oil and water causes them to mix together.
Not every substance causes oil and water to mix. Vinegar does not act as an emulsifier and so does not help oil and water to mix.
Source: https://www.allrecipes.com/article/how-to-emulsify-vinaigrette/
Our Self- Evaluation
Strengths
Further research questions
Arising from our project we have identified other questions we could explore in the future including:
- In groups we used tablets to look up information on oil and water.
- We discovered that oil and water are immiscible because water is polar (each water molecule has a positive and negative charge, sort of like magnets).
- Opposites attract, so the negative end of one water molecule is attracted to the positive end of another. Water-based liquids can easily form bonds as a result.
- Oil molecules are non-polar, so they don’t have negative and positive charges and therefore they are not attracted to the water molecules.
- Oil is also less dense than water, so it floats on the top of water.
- Water and oil can be made to mix by adding reducing the surface tension of water or by adding an emulsifier. Oil never dissolves in water, however.
- Emulsifier molecules have a water-loving end (hydrophilic) which bond to the water molecules, and a water-hating end (hydrophobic) which bond to the oil molecules.
https://wonderopolis.org/wonder/why-dont-oil-and-water-mix
https://mocomi.com/why-oil-and-water-dont-mix/
https://www.youtube.com/watch?v=mPob0pVvVzg
https://www.youtube.com/watch?v=h5yIJXdItgo
https://www.youtube.com/watch?v=vSXTBnnx4OA
Our experiment
- In groups we discussed and designed various ways that we could test if oil and water can ever mix.
- We had to make sure that our experiments used the same amount of oil and water and that everything was the same in each experiment except one variable (fair test). We used a control to prove that oil and water don’t usually mix. We also had to be sure no one got hurt and to keep an open mind and report our findings accurately (ethics).
- We researched what might make oil and water mix on the school tablets.
- Our teacher gathered the materials for the experiments.
- Our research question: Do oil and water ever mix?
- Our hypothesis: That some substances might make oil and water mix.
- Materials: 6 Kilner jars, measuring jug, vegetable oil, water, whisk, washing up liquid, egg, mustard, vinegar.
The control - oil and water.
Aim: To demonstrate that oil and water do not usually mix.
Part 1:
- We filled one basin per group with water. We dropped oil paint onto the surface of the water and stirred it with a paintbrush to mix the colours.
- We carefully placed a sheet of paper flat onto the surface of the water and the oil paint stuck to it, creating lovely patterns. See folder.
- We filled a Kilner jar to the label line with vegetable oil, then poured in 200ml of water.
- We observed the jar and noticed that the oil rose to the top and separated from the water.
- When we shook the jar the oil and water mixed temporarily, but then separated again, and remained separate. See Jar 1.
Whisking
Aim: To see if whisking oil and water causes them to mix together.
- We filled a Kilner jar to the label line with vegetable oil, then poured in 200ml of water.
- Each child in the group took turns vigorously whisking the oil and water.
- While it was being whisked we observed that the oil and water mixed, but once the jar was allowed to settle, the oil and water separated, and stayed separate. See Jar 2.
Whisking oil and water together causes them to mix, but only temporarily. It breaks the oil and water molecules apart and mixes them up amongst each other, but there are no bonds formed, and so they separate once again the whisking stops.
Whisking would help the oil molecules to be completely coated if adding an emulsifier, so can be useful in creating an emulsion when another substance is added.
Washing-up liquid
Aim: To see if adding washing-up liquid to oil and water causes them to mix together.
- We filled a Kilner jar to the label line with vegetable oil, then poured in 200ml of water.
- We poured washing-up liquid into the jar and shook it vigorously.
- We allowed the jar to settle. At first the oil and water remained mixed but after a while they seemed to separate again. See Jar 3.
Washing-up liquid helps water and oil to mix. From our research we know that this is because washing up liquid is a surfactant. As well as bonding to both the oil and the water, a surfactant helps reduce the surface tension of water. Surface tension is the force which helps a blob of water on a surface hold its shape and not spread out. Washing up liquid helps break apart these forces.
Source: https://www.york.ac.uk/res/sots/activities/soapysci.htm
Mustard
Aim: To see if adding mustard to oil and water causes them to mix together.
- We filled a Kilner jar to the label line with vegetable oil, then poured in 200ml of water.
- We poured a large spoonful of mustard into the jar and shook it vigorously.
- We allowed the jar to settle. The oil and water mixed and remained mixed. See Jar 4.
Mustard was the best substance we tested for mixing the oil and water together. From our research we know it is an emulsifier because mustard seeds contain a sticky substance called mucilage, that coats oily particles and allows them then to bond with water molecules.
Source: https://www.ochef.com/why-is-mustard-a-good-emulsifier
Egg yolk
Aim: To see if adding egg yolk to oil and water causes them to mix together.
- We filled a Kilner jar to the label line with vegetable oil, then poured in 200ml of water.
- We spooned an egg yolk into the jar and shook it vigorously.
- We allowed the jar to settle. The oil and water mixed, but after a while appeared to separate.
- We added a second egg yolk and shook the jar again. The oil and water mixed and remained mixed.
- See Jar 5.
Egg yolk helps oil and water mix. We know from our research that it is an emulsifier because it contains lecithin. The albumin protein in egg white also make it an emulsifier. Eggs are widely used in cooking because of their emulsifying properties.
Source: https://homekitchentalk.com/is-egg-an-emulsifier/
Vinegar
Aim: To see if adding vinegar to oil and water causes them to mix together.
- We filled a Kilner jar to the label line with vegetable oil, then poured in 200ml of water.
- We added vinegar into the jar and shook it vigorously.
- We allowed the jar to settle. The oil and water remained separate.
- See Jar 6.
Not every substance causes oil and water to mix. Vinegar does not act as an emulsifier and so does not help oil and water to mix.
Source: https://www.allrecipes.com/article/how-to-emulsify-vinaigrette/
Our Self- Evaluation
Strengths
- We tried to make sure it was a fair test by keeping all the factors the same, apart from the addition of one variable each time.
- It was ethical, as no person or animal was harmed during the experiments.
- We reported our findings fairly and accurately, and paid attention to the limitations of our study.
- We mainly used vegetable oil in our experiments- we could have used different types of oils to see if we got the same result. (We did try mix oil paint and hydraulic oil with water).
- We only experimented with a limited number of substances- there are lots of other substances that we could have tried.
- While we took the water from the same tap each time and so presumably it was of the same temperature, we didn’t actually check this, which would be a limitation if the water temperature varied.
- We didn’t measure the amount of emulsifying agent we added to each experiment
Further research questions
Arising from our project we have identified other questions we could explore in the future including:
- Does the ratio of oil to water affect how immiscible it is?
- Is there a certain amount of emulsifying agent that you have to put into the oil and water in order for an emulsion to form?
- Do different types of oil behave differently?
- Does the size of the container influence if the oil and water mix?
- Does oil mix with other substances, e.g. milk, cola etc.?
- Does stirring/shaking/spinning affect the creation of an emulsion?
- Does the temperature of the oil and water matter?
- Are there other substances that don’t mix together under normal conditions?
- Is the fact that oil and water don’t mix easily useful? What does it affect?
- Does an emulsion last or do the oil and water separate again after a while?