Victoria

toc =**__Non-Newtonian Fluid (a.k.a Cornstarch + Water)__**=

When you mix cornstarch and water together, it creates a special mixture sometimes called a [|oobleck]. Cornstarch and water is a [|non-newtonian fluid], which has properties of both liquids and solids.

__Plan:__
To be familiar with a substance that is neither solid or liquid and to figure out what is happening.

__Hypothesis:__
Mixtures with higher concentration would be stiffer and harder to move. Mixtures with higher temperature would be more smoother and easier to move.

__Materials:__
Cornstarch (a lot) Water Scale Beakers Scoop Thermometer Heating plate Fridge OR Ice Various small objects Oven

__Variables to test:__
Concentration Temperature

__Things to discover:__
How far something can sink (Is it like quicksand, and stops at a certain point? Or does it keep going?) What it will look like when it has been heated (cooked/baked. Will it look like bread?) What will happen when it is frozen? And then defrosted? What will happen if you left it out for a while? Is it flammable? What happens if it is thrown in the air?

Concentration:
1. Fill up five beakers with 100ml of water 2. In each beaker, put 125ml, 150ml, 175ml, 200ml, and 225ml of cornstarch respectively. 3. Mix each carefully and thoroughly 4. Play with it, throw it in the air, etc. 5. Take down observations. 6. Observe the differences and the properties of these mixtures.

Follow Up:
__What will happen if you left the mixture out for a while?__ 1. Leave the 125ml, 175ml, and 225ml mixtures out to settle, and see what happens. 2. After observations have be taken down, see if the mixtures can be remixed if it has settled.

Second Follow Up:
__How far can something sink?__ 1. Use the 150ml and 200ml mixtures and place various small objects in each to see what happens. 2. Take out the objects to reuse the mixtures.

Temperature:
//If they mixtures look normal, then mix them all together. This will make a concentration of [(62.5 + 75 + 87.5 + 100 + 112.5)/ 5 = 175] 175 grams of cornstarch every 100 ml.// 1. Make sure the mixture is mixed thoroughly, then separate it into 5 equal parts, each in its own beaker. 2. Put one in a freezer, a refrigerator, at room temperature, and heat the last two to two different temperatures. 3. When they are at your desired temperature, play with it with your hand, throw it in the air, etc. 4. Take down whatever observations you have made.

Follow Up:
__What happens if you bake it?__ 1. After you allow the mixtures to cool, place some in a baking tin, and some on a baking tray, and bake it in an oven. 2. When this is complete, take down any observations.

//([|This site] says that the ratio of cornstarch to water in a non-newtonian fluid mixture is 2:1 to 3:2. This means that to make non-newtonian fluid, there should be 1.5 to 2 times more cornstarch than water.)//

What I saw:
__Concentration:__ The more cornstarch added to the water, the thicker it is. This meant that it was harder for things to sink or move around, and the mixture itself moved slower if poured. The more water that was added, the thinner it was. There was a smaller resistance if a finger was pushed in, and it flowed more freely when it was poured. __Temperature:__ The higher the temperature of the mixture, the thinner it is, making it easier to move and have less resistance. The lower the temperature, the stiffer it gets. - When the cornstarch and water mixture was frozen for a few days, the beaker seems to have cracked along the bottom. Either this happened because the mixture had expanded too much for the beaker, or someone had dropped it. The mixture seemed exactly the same after it was defrosted, if not a little thick from the evaporation of the water from the heating. - We didn't have the equipment needed to bake the mixture, but when it was heated, the water would evaporate, leaving the cornstarch in the beaker. This caused the mixture to be thicker. - When I was melting the frozen mixture, the cornstarch and water seemed to heat slowly. The frozen mixture was about 12 degrees centigrade when it was melting, and the melted mixture was rising from about 24 degrees. __Extras:__ - When something is put into the mixture, it sinks slowly. Unlike quicksand, the object sinks all the way to the bottom. - If the mixture is left out without any disturbances at room temperature, the water begins to evaporate, leaving the mixture more concentrated and thicker. - Cornstarch and water is not flammable. - When a piece of cornstarch and water is thrown in the air, it acts like a liquid while it is suspended. When it lands however, it acts like a dense solid; it splats down without bouncing, and feels like a solid. When a piece is thrown onto a table, the mixture turns hard, and then starts to 'melt' into a liquid, flowing everywhere.

The Science Behind This Experiment:
When cornstarch is added to water, a physical action takes place, called suspension. The mixture makes something called a non-Newtonian fluid, which is the name given to substances with properties of both solid and liquid. When you stab or puncture it quickly, the substance seems to be hard and solid-like, but when you do it slowly, the substance seems to be like liquid. When some water had evaporated, I added more water, and it returned back to the way it should be. This made me be certain that the change that happened was a physical change. If the beaker wasn't dropped during the freezing, I think that the reason it broke was because the mixture expanded too much for the beaker to withstand. If a bit of the mixture was dropped onto the table or the floor, the water would have soon evaporated, leaving only the cornstarch behind. I thought that the mixture would be thicker when it was more concentrated, because I figured it would be like salt water. If there is more salt, then the water tastes saltier. If there is more starch, the mixture would be more like starch, which is a solid. Next time I would try more experiments that make substances like cornstarch and water, and compare them to each other. I would also find the perfect ratio for cornstarch to water.