When you look at a glass of water, everything seems quite still. You cannot see the water moving around. Robert Brown made an interesting observation about a drop of water that was important to the development of the modern theory of heat.

Read about his discovery on pages 82 and 83 of your textbook.

Question 1. What was Robert Brown doing when he observed the phenomenon called Brownian Motion?

Question 2. When he saw the pollen grains bouncing and jiggling around in the drop of water, what was his first explanation for this motion?

Question 3. What do you think made him change his first explanation and think of another explanation for the jiggling motion of the pollen grains?

 

Then, return here to continue this lesson.

 

Now,

  1. Read the Disc Connect activity on page 83 of your textbook.
  2. Insert the Science.Connect 1 CD into your computer CD player.
  3. Launch the Brownian Motion applet.
  4. Follow the instructions.

Question 4. What name is given to the jiggling, zigzag motion of microscopic particles?

Question 5. What was the name of the French scientist who traced the paths of microscopic particles and made maps of their motion?

Question 6. The particles that bump into the pollen grains were called molecules of water. Did Robert Brown call these molecules of water?

Then, continue this lesson.

 

 

 

 

 

 

 

 

 

 

 

Answers to Questions:

Question 1. What was Robert Brown doing when he observed the phenomenon called Brownian Motion?

He was studying pollen grains under a microscope.

Question 2. When he saw the pollen grains bouncing and jiggling around in the drop of water, what was his first explanation for this motion?

At first, he thought that the pollen grains were alive.

Question 3. What do you think made him change his first explanation and think of another explanation for the jiggling motion of the pollen grains?

The jiggling motion increased when he heated the water. If the jiggling motion was related to the temperature of the water, it could not be related to the pollen grains moving by themselves.

 

Click to return to where you left off in this lesson.

 

 

 

 

 

 

 

 

 

 

 

Answers to Questions:

Question 4.What name is given to the jiggling, zigzag motion of microscopic particles?

Brownian motion.

Question 5. What was the name of the French scientist who traced the paths of microscopic particles and made maps of their motion?

Jean Baptiste Perrin.

Question 6. The particles that bump into the pollen grains were called molecules of water. Did Robert Brown call these molecules of water?

No, Robert Brown was not sure what the particles were. Other scientists speculated that the particles were atoms or molecules.

Now, do Assignment 5A. Page forward to access the computer-scored assignment.