Week 2 Science Investigation – (Milk) Colours, Colours and More Colours

Week 2 (7th March 2012)

The aim of this investigation is to explore the components of milk. Today, we are faced with the choice of many types of milk (low fat, skim, full cream etc). This investigation will answer these questions: What is the difference between these types of milks? Why are there so many types of milk? What makes them different?

Focus Question: What chemical reaction will happen when a drop of detergent is added to a bowl of milk with a drop of food colouring in it?

When detergent is added to the milk/food colouring plates, it will instantly send the food colouring to the edges of the bowl, and begin to swirl the milk around.

Materials List

  • Fat milk
  • Soy milk
  • Lite milk
  • 3 plastic bowls/ plates
  • Eyedroppers
  • Red & Blue food colouring
  • Dishwashing Detergent

    1. Place a small amount of each three milks into three separate bowls.
    2. Place a drop of red food colouring into the milk. Do not stir.
    3. Place a drop of blue food colouring into the milk. Do not stir.
    4. Place a drop of detergent on the milk.
    5. Observe closely and record what is happening in each of the 3 bowls.

Raw Data / Observations / Diagrams

Observation Chart of Milk Experiment

Milk Types
Fat Milk
Lite Milk
Soy Milk
Food Colouring

(Red and Blue)
Red Dye - Spread and expanded through milk
Blue Dye - Kept to itself and did not spread

The prediction was it would separate and spread through the milk
Red Dye - Stayed where it was dropped (turned a blood red)
Blue Dye - Stayed where it was dropped

The prediction was similar to the “fat milk”, just not as good
Red Dye - Stayed in drop (turned a dark red)
Blue Dye - Stayed in drop and sunk to the bottom of the plate (turned a dark blue)

The prediction was not much movement will occur

(Home Brand)

When detergent was dropped the food colouring separated then a chemical reaction happened and made the food colours swirl. It stopped after a couple of minutes, and started to mix
From the position of the food colouring drops, the colour got pushed to the side of the plate – less movement than the “fat milk”
Detergent stayed in position where it was dropped (middle of plate) and did not move around the plate like what happened in the “fat milk”.

The blue and red food dye did not mix or swirl as much when detergent was added, the colours separated to either side of the plate
Other Observations
  • When detergent was added, all 3 milks pushed out to the edge of the plate, and came back to the centre (in a roll/swirl effect)
  • Blue food colouring was more dominant than the red food colouring
  • The “fat milk” and “lite milk” reacted better to the detergent
  • In the “soy milk” and the “lite milk” (before the detergent was added) the food colouring drops didn’t spread or expand through the milk
  • Detergent had a rolling effect when the food colours were mixing
  • We did not place the food colouring drops in the same positions in the 3 milk plates to know if it would effect the detergent mixture
  • When we added dye to “fat milk” it instantly reacted and spread, but the blue dye did not react the same as the red dye
  • “fat milk” spread the fastest when the detergent was added, “lite milk” was a little slower, and “soy milk” took a lot longer to spread
  • In the “soy milk” the detergent stayed in one place (in the centre of the plate where it was dropped) unlike the other 2 milks the detergent moved around the plate (‘chasing the colours’)

The results show that when a drop of detergent is added to a bowl of milk with a drop of food colouring in it, the food colouring and the milk separate at first, the food colouring is sent to the side of the bowl, then both the milk and food colouring mix and begin to swirl from the centre of the plate outwards to the edges, then back into the middle and around the plate.

The food colouring was added to the milk to make the chemical reaction visible. The chemical reaction occurs because When we add food colouring to the milk, nothing happens. BUT, when the dish detergent touches the milk, things start to move. The surfactants reduce surface tension, which allows the food colouring to spread around the milk. Then the enzymes start to react with the calcium, proteins and fats in the milk, which causes the colour pigments from the food colouring to get pushed around, resulting in a cool colourful pattern” (Lahav, 2012).


Was it a fair test?
  • YES / NO
  • Equal amounts of milk were measured and poured into equal sized bowls
  • The same brand of red and blue food colouring was used
  • Uneven (drops) amounts of food colouring were dropped into the milk (this may of effected how much of the chemical reaction was observed/ occurred)
  • The food colouring was dropped into the milk in different positions of the bowls (not always dropped in the centre of the bowls)
  • There were also uneven amounts of detergent dropped into the bowls of milk
  • Detergent was also dropped in different positions of the bowl
  • Two different brands of detergent were also used (which could have had different active ingredients)
  • More than one person was performing the experiment (each person used different techniques)
  • The bowls that the experiments were performed in were physically moved or bumped which could of affected the chemical reaction / results

What information did you collect and in what form?
  • The information collected from conducting the experiment was the chemical reactions that occurred when a drop of detergent was added to a bowl of milk with a drop of food colouring in it.
  • Collected the information in the form of digital photographs/ videos and observation notes (this included: what was occurring / the chemical reactions)

How else could you collect information?
  • Collect information on the approximate time duration of the chemical reactions in the milk

How could you record it?
  • Use a stopwatch to time the approximate duration of the chemical reaction when the detergent is added to the milk.
  • Record times in a table of results – e.g.

Results Table of Chemical Reaction Time
Milk Type
Detergent Added (chemical reaction time)
These extra columns could be used to repeat the experiment a number of times to test accuracy or to find averages
Full Cream


Lite milk

Could you improve the experiment procedure?
  • YES – How?
  • Make the experiment more of a fair test by performing the experiment a number of times instead of just once
  • Allocate a constant (or controlled variable) an element that you won’t change, a variable (element that will change) and a dependent variable (what will be measured).
  • Allocate each participant a specific job/part that they stick to (this will keep the experiment fair)
  • Relate the experiment to a real-life context or situation, this way the participants will have more of an interest in conducting the experiment – therefore the results/discussion will be more detailed.

Follow up Investigations:
  • Leading on from this milk investigation, you could explore the question what would happen if there was no fat in the milk? Would there still be a chemical reaction when the detergent is added? This would provide more of an understanding of the chemical reactions that occurred and why they occurred in the milk experiment.
  • Move on from using milk – try the experiment using a controlled variable (water or juice) to answer the above questions.


References / acknowledgements

Lahav, Oren., 2012., Chemistry Experiment: magic milk.,