BIOLOGY CHEMISTRY Experiment 1 - Molecular Weight and Diffusion Rate Molecular w

Question

BIOLOGY CHEMISTRY

Experiment 1 - Molecular Weight and Diffusion Rate

Molecular weight is an indication of the mass and size of a molecule. The purpose of this experiment is to determine the relationship between molecular weight and the rate of diffusion through a viscous medium. You will investigate two dyes.

Molecule

    Molecular weight

Blue Dye Solution

    793 grams/mole

Red Dye Solution

    496 grams/mole

Materials

Red and Blue Dye Solutions

1 Bottle of Corn Syrup

1 – cm Petri Dish (top and bottom halves)

Stopwatch or Timer

Small plastic metric ruler

White piece of paper, index card, or white paper towel *

   * you provide

Procedure

1. Take the petri dish and fill both halves with corn syrup until about ½ - ¾ of the way to the top. Place one half on top of a white piece of paper. Place the small clear plastic ruler under the dish

3. Place a single drop of blue dye in the middle of the corn syrup,

4. Note the position where the dye fell by reading the location on ruler.

5. Measure the diameter of the dye (the distance across the widest part of the circle) after ten seconds and 20 seconds. Record your data in Tables 1 and 2.

6. Repeat steps 3 – 5 using the red dye.

Table 1: Rate of Diffusion in Corn Syrup

Time (sec)

Blue Dye

Red Dye

10

20

Questions

1. Which dye diffused the fastest after 10 seconds?

2. Does the rate of diffusion correspond with the molecular weight of the dye?

3. Does the rate of diffusion change over time?

4. If the dishes were left to sit overnight, the next morning would you expect the diameter of the dye to be similar or different?

Molecule

    Molecular weight

Blue Dye Solution

    793 grams/mole

Red Dye Solution

    496 grams/mole

Explanation / Answer

1.according to the experiment result is red dye so conclusion is that red dye diffused faster after 10 seconds.

2. Yes the rate of diffusion is corrospond to with the molecular weight of dye because red dye contained less molecular weight and have less gravitational friction so it can diffused faster.

3. Yes it changing over the time because in starting if we drop a dye its concentration is high and spread faster but over the time its concentration became less so moving rate also decreased so in this way we can say that diffusion is directly proportional to concentration gradient .

4. I expect that diameter would be similar because both dye have a lot of time to express their concentration gradient whether their diffusion rate will be different but over night is the sufficient time to diffused completely .

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