Bio 103 - Introduction to Biology

Chapter 5: The Working CellDemonstrating Diffusion

Background: Molecules must move about in a cell in order for a cell to survive. In this activity, you will see the movement of molecules and study how temperature affects this movement.

Objectives: • observe diffusion. • recognize the relationship between temperature and the rate of diffusion.

Materials: • goggles • clear, microwavable containers (3), 400 mL • water • ice cubes • microwave• insulated glove - oven mitt• hot pad (optional) • thermometer • food coloring • timer

Preparation: Label three clean 400 mL microwavable containers Cold, Medium, and Hot, respectively.

Procedure: 1. Add cool or lukewarm tap water to each container until it is approximately half full. 2. Place two ice cubes in the Cold container. Set both the Cold container and the Medium container aside. 3. Place the Hot container in the microwave and heat the water to boiling. 4. Use an insulated glove or oven mitt to carefully remove the container from the microwave. Use the hot

pad when placing hot objects on surfaces that are not suited for high temperatures. 5. Use a thermometer to find the initial temperature of the water in each beaker. Record your results in

a table similar to the one shown. 6. Do not shake or stir the water. Add five drops of food coloring to the container. Note the time

required for the coloring to spread uniformly through the water. Record the result. 7. Remove the ice cubes from the Cold container. If necessary, add cold water to the container until its

level is about equal to that of other containers. 8. Repeat steps 5 and 6 for the Cold and Medium containers.

Temperature of container

Cold Medium Hot

Initial Temperature

Time of Diffusion

1 success = preparation + execution

Analysis: Complete the following questions using information from this laboratory activity and the chapter’s information.

1. An operational definition is a definition based on observation. State an operational definition of diffusion based on your observations of the food coloring in the containers.

2. Explain how temperature affects diffusion.

3. Why is a warm body advantageous for a living thing?

2 success = preparation + execution