Agar Jelly Experiment Report

Aim:

To find out the speed of diffusion in agar jelly, when there are three blocks of jelly of different sizes.

Material:

A container with agar jelly, safety goggle, knife, ruler, stop watch, a glass plate, sodium hydroxide, an indicator.

Method:

First, we took the block of agar jelly from the container. We placed it onto the glass plate, and took our knife and ruler. We measured and cut the block, making three cubes of different measurements. The smallest one is 1cm by 1cm by 1cm, the second one is 2cm by 2cm by 2cm, and the biggest one is 3cm by 3cm by 3cm. We then dropped a few drops of the indicator. Next, we put our safety goggles on, and took the beaker full of sodium hydroxide, and poured it into the glass plate, which the cubes are in. At the same time, we started the stop watch. We saw everything, the cubes, sodium hydroxide turn pink (that’s because sodium hydroxide reacted with the indicator). When the stop watch showed 5 minutes, we took the cubes, and cut all of them in half. Then we measured the distance from the surface, to the line where the pink and the white color separate, like on the diagram, using our ruler. We recorded what we saw, and the results.

Results:

We saw the cubes turn pink, and the sodium hydroxide turn pink on the plate. We also saw, when we cut the cubes that the pink color travelled into the cube, and we saw that at a certain point, there was the separation of pink from the surface, to white, the color of agar jelly. Like I said, we measured the distance between the surface to where the separation line of pink and white color was. This is what we got:

1cm*1cm*1cm 4mm

2cm*2cm*2cm 4mm

3cm*3cm*3cm 4mm

Although they were all 4mm, we saw that the smallest cube was almost completely ...

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Results:

1cm*1cm*1cm 4mm

2cm*2cm*2cm 4mm

3cm*3cm*3cm 4mm

Although they were all 4mm, we saw that the smallest cube was almost completely diffused, almost everything was pink. And we saw that the biggest cube was not at all completely diffused; most of it was white inside the cube.

Speed of Diffusion=Distance/Time

4mm/5minutes=0.8mm/minute

Conclusions:

From this experiment, I learned these things:

Firstly, I learned that the pink color traveled into the cube, because of diffusion. Diffusion is when particles move from an area of high concentration to an area of low concentration. So in this experiment, the sodium hydroxide diffused from the high concentrated area (which is the surface of the cube, as sodium hydroxide was poured onto the cube) to low concentrated area (inside the cube). I also learned that even if you change the volume, or the surface area of the agar jelly, the speed in diffusion doesn’t change. As you can see from the results, no matter the size of the cube, the sodium hydroxide diffused at the same speed. The speed of diffusion can be calculated by distance/time. In this experiment, we saw that the distance which the sodium hydroxide traveled was 4mm, and the time we used was 5 minutes. So, 4mm/5min= 0.8mm/minute.

Because the speed doesn’t change, the smaller the cube, the faster it’ll get completely diffused.

From this experiment, I can expect that 1cm*1cm*1cm cube jelly will be completely diffused in 6minutes 15seconds, because 1cm/0.8mm*2=6.25min. (times 2 because it diffused from the top and the bottom). In the same way, I calculated that 2cm*2cm*2cm cubed jelly will be completely diffused in 12.5minutes and 3cm*3cm*3cm jelly in 18.75minutes. You can see that 2cm*2cm*2cm jelly will take twice as much time as 1cm cubed one and 3cm*3cm*3cm jelly will take three times as much time as the 1cm cubed block.

Teacher Reviews

Here's what a teacher thought of this essay

Cornelia Bruce

1st of Dec 2012

3* This is a standard biology laboratory report on diffusion. The layout is standard, however does leave out some key information including an introduction and evaluation, where the biological significance of the experiment should be noted. The method should be written more clearly and include a labelled diagram. The experiment was straight forward with a variety of volumes used, to improve this more agar jelly cubes could have been tested using repeats to more clearly establish the rate of diffusion.

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