Part A: Working Scientifically

Investigation 1 – How well does dishwashing liquid repel against fat?

Introduction

Prior to completing the activity I wrote down what I think would happen when I added dishwashing liquid to various types of milk, these being full cream, smarter white and skim milk.

We placed 1 drop of red food colouring on one side of the bowl and a drop of blue food colouring on the other side of the bowl directly opposite the red colouring. Both drops were about 5cm in from the edge of the bowl.

Predict

My prediction is that once the dishwashing liquid was added to the bowl that contained the full cream milk, the colours would dissolve and disappear. I predicted that this would happen to all 3 types of milk, however I believe that the colour would not fade as much in the skim milk as they did in the full cream milk. I believe that this would occur due to the dishwashing liquid reacting to the food colouring in the milk.

Observe

When we placed the drops of food colouring in the bowl we saw that it did not move it just stayed as a drop in the bowl of milk. We then added the dishwashing liquid in between the food colouring and as soon as we did this the food colouring reacted by moving away from each other to the outer rim of the bowl.

The food colouring sank into the milk for the first part and there was a small thin outline of the food colouring around the edge of the bowl that

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went for about 5cm. We watch the bowl and we could see that nothing was happening as we continued to watch the bowl we noticed that the colours were starting to move and react to the dishwashing liquid.

As a group we asked ourselves “what was moving”? “What was happening”? We noticed that the colours were swirling in the milk and we believed that there was a reaction with the detergent and the milk. Some of the suggestions that we came up with as to what was happening was that perhaps the milk was separating or was curdling. We did notice that the two colours separated from each other, moving to opposite sides of the bowl. We also considered whether the reaction was due to the food colouring being in the milk or would it still have the same reaction if the food colouring was not in the milk.

We completed the investigation again however this time we used the “smarter milk which had 2% fat. We again put the drops of food colouring in the bowl followed by the dishwashing liquid in the middle of the food colouring. This time the reaction was the same in the fact that the food colouring sank, and then began to swirl around however the reaction was a lot slower and did not go for as long as what it did with the full cream milk.

The third investigation was to complete it again, however this time we used skim milk. When we put the dishwashing liquid into the milk and this time the colours actually swirled together, but did not mix. The blue colouring sat on top of the red colouring but they did not mix together.

Explain

We know that the reaction that we were seeing was in the dishwashing liquid repelling against the fatty milk. It was not the food colouring that was repelling against the milk or detergent and the colouring was there to help show how the milk was reacting to the dishwashing liquid.

Steve Spangler explains that the reason it reacts like this is “due to the detergents bipolar characteristics (nonpolar on one end and polar on the

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other), weakens the chemical bonds that hold the proteins and fats in solution. The soap's polar, or hydrophilic (water-loving), end dissolves in water, and its hydrophobic (water-fearing) end attaches to a fat globule in the milk”.

He continues on to explain that “The molecules of fat bend, roll, twist, and contort in all directions as the soap molecules race around to join up with the fat molecules. During all of this fat molecule gymnastics, the food coloring molecules are bumped and shoved everywhere, providing an easy way to observe all the invisible activity. As the soap becomes evenly mixed with the milk, the action slows down and eventually stops.

We can see from the evidence of the photo below the milk reacting to the detergent.

So we can look back at our question for completing this investigation – How well does dishwashing liquid repel against fat? I think that we can clearly establish that it actually repels more intensely as the milk with the higher fat content had a more significant reaction than the milk with the lower fat content.

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Part B: Australian Curriculum – ScienceScenario 2 – Year 3/4StrandSub- strand

Aims Learning Design (around scenarios)An interest in science as a means of expanding their curiosity and willingness to explore, ask questions about and speculate on the changing world in which they live.An understanding of the vision that science provides of the nature of living things, of the Earth and its place in the cosmos, and of the physical and chemical processes that explain the behaviour of all material thingsAn understanding of the nature of scientific inquiry and the ability to use a range of scientific inquiry methods, including questioning; planning and conducting experiments and investigations based on ethical principles; collecting and analysing data; evaluating results; and drawing critical, evidence-based conclusionsAn understanding of historical and cultural contributions to science as well as contemporary science issues and activities and an understanding of the diversity of careers related to science

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A solid foundation of knowledge of the biological, chemical. Physical, Earth and space sciences including being able to select and integrate the scientific knowledge and methods needed to explain and predict phenomena, to apply that understanding to new situations and events, and to appreciate the dynamic nature of science knowledge.

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Referencing

www.stevespanglerscience.com

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