Intensive versus Extensive Properties

Description

Intensive properties (temperature, pressure) do not depend upon the sample size. Extensive properties (mass, volume) depend upon sample size. Two identically sized portions of a solution are prepared. One portion is then arbitrarily subdivided into three subportions. For intensive properties, the value of the property for each subportion is the same. For extensive properties, the sum of the values of the property for the subportions equals the value for the whole portion.

Go to Top

1. Fill the 400-mL beaker with colored water. Select a student from the class to divide the colored water between the two 250-mL beakers until each beaker contains "exactly the same amount."
2. Once they have done this, take one of the beakers and distribute its contents among three smaller beakers.
3. Mass is an example of an extensive property. "The mass in this beaker plus the mass in this beaker plus the mass in this beaker equals the mass in this beaker."
4. List 4 extensive properties.
5. For intensive properties, "The temperature in this beaker equals the temperature in this beaker equals the temperature in this beaker equals the temperature in this beaker."
6. List 4 intensive properties.

Go to Top

Name ___________________________ Class ________

Teacher__________________________

DoChem 015 Intensive versus Extensive Properties

Watch the movie and answer these questions.

1. Describe the demonstration.
2. List 4 extensive properties.
3. List 4 intensive properties.

Go to Top

Purpose

To illustrate the distinction between intensive and extensive properties.

Go to Top

• 1 400-mL beaker
• 2 250-mL beaker
• 1 150-mL beaker
• 1 100-mL beaker
• 1 50-mL beaker
• 400 mL tap water colored with food coloring

Go to Top

This illustration is quickly and easily set up in the classroom.

Go to Top

Teacher preparation: 5 minutes

Presentation Time: 10 minutes

Go to Top

There are no unusual hazards in this experiment.

Go to Top

No special precautions are required in this experiment. Follow routine laboratory precautions.

Go to Top

Discard the water at the sink.

Go to Top

1. Fill the 400-mL beaker with colored water. Select a student from the class to divide the colored water between the two 250-mL beakers until each beaker contains "exactly the same amount."
2. Once they have done this, take one of the beakers and distribute its contents among three smaller beakers.
3. Ask the students to call out properties. For extensive properties (such as mass, volume, heat content, moles) say while pointing to each of the appropriate beakers in sequence "The mass in this beaker plus the mass in this beaker plus the mass in this beaker equals the mass in this beaker."
4.  For intensive properties (such as temperature, pH, vapor pressure, density) say while pointing to each of the appropriate beakers in sequence "The temperature in this beaker equals the temperature in this beaker equals the temperature in this beaker equals the temperature in this beaker."

Go to Top

1. The distinction between intensive and extensive properties often escapes students and is a cause of fundamental misconceptions about chemistry. This illustration is helpful to some students in overcoming this difficulty.
2. Some properties (surface area, color, color intensity, shape) may cause trouble when called out. Rather than respond to those which cannot be easily placed into one of the two categories, defer answering them until a later time. You may need to do some research for some of the properties named.
3. A formal way to represent this problem, but one which is usually beyond the developmental stage of the students, is to identify a property of the material in the 250-mL beaker as B, and that in each of the smaller beakers as bi.
4. In this case, for intensive properties, B = bi.
5. For extensive properties, B = S bi (in this case, B = b1 + b2 + b3).

Go to Top

• Extensive properties-mass, volume, heat content, moles, length
• Intensive properties-temperature, pH, vapor pressure, density, concentration

Go to Top

• property
• intensive property
• extensive property
• mass
• volume
• temperature
• pressure

Go to Top