Details Activity Length 30 mins. Topics ArtMixtures Activity Type Discrepant Event (Investigatable) Language English Publish

In general, fat and also water do not mix; liquids prefer these that carry out not form a homogeneous (uniform) mixture are called immiscible.

When food colouring is placed on the surface of milk, the drop remains intact with bit spanalysis. The water-based food colouring does not mix via milk conveniently, because milk is a suspension of fat molecules in water and food colouring is a water-prefer dye.

Once the soap is added to the milk, it spreads over the surchallenge and causes the food colouring to move quickly thounstable the milk and out to the edges of the plate. Because milk is largely water, it has actually a surchallenge stress like water. Liquid soap wrecks the surface tension by breaking the bonds in between water molecules.

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After the initial zing of the food colouring, swirling of colours ensue as a result of the chemical structure of soap. Soap moleculeshave both properties of non-polarandpolarat opposite ends of theirmolecules.

The fat in milk is non-polar. The non-polarhydrocarbon tail of thesoapdissolves into the fat. The fat-choose end of the soap molecules join with the fat in the milk and as the soap spreads throughout the surconfront of the milk, even more and more fat molecules are pulled by the spreading soap. When the fat molecules congregate, the polar water in the milk is pushed ameans, taking the food colouring through it. The motion of the milk decreases as the soap becomes “provided up", or attached to all the molecules for which it has actually room.

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Objectives

Appreciate how soap permits fats or oils to mix through water based options.

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Appreciate the liquids have surconfront stress and that soap affects it.

Materials

Per Student or Group:Homogenized milk (at room temperature)Aluminum pie plateFood colouringDish detergent/liquid soapCotton swabs or tiny droppers

Key Questions

What happens best away? What happens after 1 minute?

What To Do

Pour room-temperature milk in to the pie plate, completely extending the bottom. Allow it to clear up.Add as much as 5 drops of food colouring to the milk (any kind of combination of colours is okay). Keep the drops cshed together in the centre of the plate.Dip the cotton finish of the swab in to the soap. Place the soapy end of the swab in the middle of the milk and host it tbelow for 2 secs (or use the dropper to introduce a drop of soap into the middle of the milk).Watch the reactivity closely. Notice what happens immediately and what happens over time.Continue to experiment by adding another drop of soap.

Extensions

What happens if you use a various type of milk? Try utilizing skim, 1%, 2% and cream. Predict if each will certainly react the exact same as the entirety milk and then test to check out if you’re right!

Other Resources

Science World Reresources | Tourbillon de lait | French version of this resource