Diffusion In A Dish

7th Grade Integrated Science Standard 1, Objective 1 Title: Diffusion in a Dish Description: An introductory diffusion activity. Materials: petri dishes (unsterile) water, beakers, food coloring in dropper bottles, laminated circles the size of the petri dishes(see below for sample, they do not have to be laminated but they will last longer if they are), student page (see below) Time Needed: 30 minutes Background: Students need to be reminded that both water and food color are made of molecules. They cannot see the individual molecules but they can see them when there are many. You might introduce this activity by spraying a strong smelling chemical (perfume, cleaner) in the room and having students raise their hands when they smell it. Discuss how particles are always moving. Procedures: 1. Show students where materials are located and read procedures from student sheet. 2. Allow students time to collect data. 3. Discuss outcomes of the experiment. 4. Give students time to answer analysis questions and conclusion. Scoring Guide 1. Students follow procedures and collect data…………………4 2. Students analyze data correctly……………………………….4 3. Students thoughtfully write conclusion………………………..4

Note: the drawings below can be resized by clicking on them and dragging the corners in or out. There are two cirlces on the page to save paper and laminating plastic.

Name___________________________________Period____________ Title: Diffusion in a Dish Introduction: Diffusion is defined as the movement of molecules from a high concentration to a low concentration. In this activity, you will observe the movement of food coloring as it diffuses in water. Materials: petri dishes, water in a beaker, food coloring in dropper bottles, paper with petri dish circle on it. Procedures: 1. Collect your materials at your table and add water to the petri dish. It should be nearly full. 2. Place the petri dish over the large circle. 3. Notice the time and add a drop of food coloring to the center of the petri dish. 4. One minute later, draw in your data the location of the food coloring. 5. At three minutes, draw again. 6. Draw again at 5 minutes 7. Draw again at 8 minutes. 8. Clean up by pouring the water back in the beaker to carry it to a sink. Prediction: How far will the food color spread in 8 minutes? Data:

1st minute

minute 3

Analysis 1. Describe the movement of the food coloring.

minute 5

minute 8

2. Why did the food coloring move?

3. What are molecules always doing?

4. What is diffusion?

Conclusion: