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KS4 Science Lesson Plan – The Creative Chemistry Of Cosmetics

Exploring unexpected topics can reveal new enthusiasm for science – and scientific careers – amongst your students, says Dr Joanna Rhodes

Dr Joanna L Rhodes
Dr Joanna L Rhodes
  • KS4 Science Lesson Plan – The Creative Chemistry Of Cosmetics

Some students struggle to find relevance in science for them and this lesson explores cosmetics and make-up as useful hooks to get more of them into chemistry. Cosmetics and make-up, as a context, provides many links across the key stage 4 chemistry syllabus including nanoparticles, emulsions and bonding. This lesson also encompasses media, ethics and the environment.

I am sure I am speaking to most teachers when I say that there is a group of students in your school who, regardless of your school’s make-up policy, arrive in pristine full-face make-up every day. Harness their enthusiasm for these beauty products to provide links to chemistry, tackling challenging topics and promoting cosmetic chemistry as a career option.

The inspiration for this lesson came when I read an advert for L’Oréal careers in New Scientist. The passage that caught my attention read:

“At L’Oréal, innovation has always been nurtured by a constant dialogue between science and marketing. It is founded on ever-more precise scientific knowledge of skin and hair around the world, but is also based on attentive listening to consumers on every continent and on the observation of their behaviour where beauty is concerned. A true source of inspiration, the great diversity of beauty rituals opens up new fields of exploration.”

I put this statement onto my whiteboard and posed a single question – “Would you be interested in working, as a scientist, for this company”. The students who responded with a “Yes” would not have been our careers officer’s normal target audience for chemistry jobs. Perhaps that should teach us a lesson too?

Starter Activity – The chemicals in our cupboard

Collect as many, soap, cleanser, shampoo and foundation bottles or tubes as you can (preferably empty) and place these around the classroom. Ask students to make a list of as many of the chemicals listed on the ingredients labels of the bottles as possible.

  • How many different chemicals are in the products?
  • Which chemicals are present in most soaps, shower gels and shampoos?
  • Which chemicals are present in most foundations?
  • Students could also investigate the claims. What do these products claim to be able to do (eg anti-ageing, shine, superior cover etc)?

Using tablets or computers ask students to identify the reasons why different chemicals are used. For example sodium laureth sulfate is a surfactant and skin cleanser, aloe barbadensis softens skin and parabens are used as preservatives. Are students surprised by the number of different chemicals in their wash bags? How does that make them feel about using the products?

Main Activity 1 – Laying the foundation

Most creams including foundation are emulsions; this gives them their creamy texture and makes them smooth to apply to the skin. Emulsifiers are molecules that stop oil and water mixtures from separating. The better the emulsifier the longer it will take for the oil and water to separate. In this activity students will compare different emulsifiers used in cosmetics and food using the following method:

1. Use a measuring cylinder to transfer 5cm3 of vegetable oil into a boiling tube.

2. Use a measuring cylinder to add 5cm3 of water to form two immiscible layers.

3. Add 10 drops of an emulsifier into the boiling tube, using a pipette.

4. Seal the boiling tube with a rubber stopper.

5. Invert the tube 10 times to mix the liquids.

6. Time how long it takes for a separate layer of oil to begin forming on the top of the mixture.

7. Repeat this 3 times so that you can calculate mean values.

Readily available substances to use as emulsifiers include: washing up liquid, egg yolk, soap powder and mustard powder. It would also be interesting to compare these with emulsifiers that are used in cosmetics which are readily available from outlets such as Naturally Thinking. You could try cetyl alcohol, glyceryl stearate, and polysorbate 20.

Main Activity 2 – High Tech Nano Screen

Many cosmetics contain nanoparticles. These tiny particles are approximately one-billionth of a meter in size. They are well suited to cosmetics because the have a high surface-area-to-volume ratio and therefore make creams including suncream, lipsticks and mascara that have superb coverage even when using a tiny amount.

To model the increased the coverage obtained by a nanoparticle use a square notepaper block (the type which is glued down one side and allows you to peel off a sheet at a time of square paper). Measure the amount of space on a table that the block takes up. Now get students to peel of the squares one at a time placing them on all the benches in the room. Compare how much of the room you can cover when you make the “particles” smaller.

In another potentially messy activity, place a tiny blob of suncream on a white tile using a glass rod. Then spread it out as thinly as possible using ideally a white plastic glue spatula. Then measure the approximate coverage area by overlaying a 1cm2 grid and counting the squares or more accurately measuring the area with a ruler. Ask students to compare different products to see which provides the best and thinnest surface coverage.

There are some concerns that nanoparticles are so small that they might pass through the skin and into the bloodstream and there is little evidence of whether they might cause harm with long term use. Ask students to read a scholarly article on the subject and write a short evaluation of the benefits and risks of nanoparticle use.

Summary – Brandstorm

Play this inspiring L’Oreal Brandstorm 2017 competition clip to your class and show the competition website:

Then, divide them into teams to create a storyboard to describe how they would showcase a new men’s grooming product. As part of the brief, students must explain the science behind the product and the reasons they hope it will be successful in the market.

You could tell students to focus their “product” on a particular type of chemistry we have looked at in the lesson such as steam distillation, emulsifiers or nano-creams.

Within their teams you could ask them to come up with a catchy name, packaging, logo and tagline for their product. You might even ask them to produce their own adverts, or video pitch in a similar vein to some of the L’Oreal Brandstorm 2017 entries:

Home learning – Microbeads and the environment

A current environmental issue surrounding cosmetics and beauty products is the use of microbeads (tiny spherical pieces of plastic, often highly coloured) found in cosmetics and other beauty products.

Give students the following quotation taken from a leading newspaper:

“UK government to ban microbeads from cosmetics by end of 2017.”

Ask students to be web detectives and to work out why the UK government would be so keen to remove microbeads from use in cosmetics. They should write their answers in the form of an information leaflet that provides the facts about microbeads and their environmental impact, the leaflet should also discourage people from purchasing and using products containing microbeads.

Download this lesson plan as a PDF here.


Dr Joanna Rhodes M.Chem, D.Phil, MRSC is Assistant Principal for Science at Shelley College in West Yorkshire.

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