"If we have a liquid that cannot be seen through it is no longer a solution. A liquid such as milk appears white because of lots of tiny drops of fat. These fat droplets prevent light from getting through the liquid. This sort of liquid is known as an emulsion as one liquid (in this case water) is surrounding tiny drops of another liquid. This arrangement may also be familiar in emulsion paint." Dr Ashworth, Futurelearn.org
Because oil and fats are lighter than water, when you for example mix salad dressings, they will go on top of the water. Therefore, they are called surfactants. Because they are surface active!
Here´s a comment from when i made the course:
"When i dipped my finger in the jar with water and oil, separated, my finger got a layer of oil, and thus the water didnt touch it. when we took water, oil and washing liquid, we shook it and after about three minute it got separated, and the water was all murky and unclear. without the washin liquid, the water was clear!"
A chemical change is something that cannot be turned back into its original state when, cooked, for example. An egg that is cooked, or a loaf of bread baked in a hot oven is two examples on this.
A physical change is something that can be turned back into a preevious state, such as, for example water that is frozen turns into ice, and then it melts into water and so on. somewhere in between it is also turned into steam, the gas form of water.
We made a chromatogram with colors and blotting paper. Below is our comment on that.
"We didnt really have blotting paper (we didnt know where to find it, and what it really is!), but in the end, we got the idea of how it worked with papertowels and such! we noticed the blue shade of the red color stayed in the bottom, while the red shade went up. Like if the red colour is more water soluble than the blue one!"
Chromatography is a standard procedure for separating and examining mixtures. There are many variations but they all rely on the fact that molecules have different interactions with one substance than with another. We saw that the iodine prefers to dissolve in oil rather than water: it is more soluble in oil than in water. In our chromatography experiment the coloured molecules that are more soluble in water are swept along easily and travel a long way. On the other hand, those that are less soluble tend to interact more with the paper and travel more slowly. <-- chromatography="" explanation="" on="" p="" thats="" the="">
I hope you got all that, and that you found it interesting and entertaining to read! /Lukas