Diffusion and Osmosis (10/10-10/14)

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Diffusion and Osmosis

This week we were learning about diffusion and osmosis looking at concentration. We also learned about the different kinds of solutions and concentrations.

Diffusion is when particles/molecules spread out. In other words, it is the movement of particles from an area of high concentration to an area with low concentration. For example, when you put a drop of food coloring into a cup with water, the food coloring will spread out trying to get to a place where there is a low concentration of food coloring. As another example, the smoke from an oven moves from the kitchen to the rest of the rooms in the house.

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Osmosis is the movement of water molecules from a high concentration of water to a low concentration of water through a semi-permeable membrane. A semi-permeable membrane (like the cell membrane) is a membrane that gets to decide which substances are allowed to pass, and which substances are not. Basically, osmosis is the diffusion of water. 

The difference between diffusion and osmosis is that diffusion can happen with any substance; however osmosis needs a semi-permeable membrane and water. 

Concentration

Concentration is the amount of something there is in a specific place. In concentration, there is a solvent, and a solute. A solvent is the liquid in a solution (in osmosis, this would most likely be water.) A solute is the solid in a solution. For example, in the ocean, the solvent is the water and the solute is the salt. 

What are the different types of solutions?

The three different kinds of solutions are isotonic, hypotonic, and hypertonic. Isotonic is when the solutions, or liquids that are mixed together become the same substance. Hypotonic is when there is less of the solution on the outside, and more on the inside. Hypertonic is when there is less on the inside, and more on the outside.

We were experimenting by putting an egg without the shell into different substances. The four different substances were vinegar, syrup, salt water, and water. Here are our results:

Liquid	Before soaking	After  soaking
Vinegar	78.9 g	78.9 g
Syrup	90.3 g	50.5 g
Salt water	83.6 g	75.2
Water	80.6 g	83.9 g

What type of solution was each liquid we used?

We know that the vinegar is isotonic because the weight of the egg stayed the same after being soaked. There was the same amount of liquid outside of the egg as there was inside of the egg.

The weight after the egg was soaked in syrup surprised everyone. I thought that the egg would loose 10 grams or less, but not about 40 grams! This means that syrup is hypertonic. There was much more of the liquid inside of the egg then there was inside of the egg.


Salt water ended up being hypertonic because it had lost weight. There was less liquid in the egg then outside of the egg.

The water ended up being hypotonic because more of the water went into the egg. There was less of the liquid on the outside of the egg, and more on the inside of the egg. 

            SP3: Planning and carrying out investigations

In class, we designed and performed experiments to test our hypotheses of which liquid was which kind of solution. I thought that the vinegar would be isotonic (which it was) because the eggs can already been soaking in vinegar a few days before the experiment. I also thought that the water would be hypertonic (which it was not.)

I think it was a good idea to perform these experiments because we could see the difference between the substances. (which would make the egg expand more, and which would not.) It helped my a lot to write this blog and understand why learning about this is important.