Specific Heat (Saeahm Kim)

Title: Properties of Specific Heat and Substances

Principle(s) Investigated: Specific heat, albedo

Standards:

HS-ESS2-2: Analyze geoscience data to make the claim that one change to Earth's surface can create feedbacks that cause changes to other Earth systems.

HS-ESS2-5: Plan and conduct an investigation of the properties of water and its effects on Earth materials and surface processes.

Materials: Heat lamp, ring stand, Petri dish (3), thermometer(s), dark-colored sand, light-colored sand, water, stopwatch

Procedure:

1. Set up the heat lamp and the ring stand so that the heat lamp is pointing directly downwards.

2. Fill up the first Petri dish with dark-colored sand, the second with light-colored sand, and the third with water.

3. Place all three Petri dishes under the heat lamp. Make sure that all three samples receive equal amounts of heating.

4. Turn on the heat lamp and begin heating the three samples for five minutes. Record the temperatures of each of the samples every minute until the five minutes passes.

5. At the end of the five minutes, turn off the heat lamp. Take the measurements of the substances as they cool for the next three minutes.

6. Graph the values of heating and cooling for all three substances on the same graph.

Use spreadsheet provided here: https://docs.google.com/spreadsheets/d/1_Bo3LRuYyGFPHzUXFSfhN-YNGzyYsMMpd0qBonhhVss/edit?usp=sharing

Student prior knowledge:

Students should understand that different substances heat and cool at different rates, and that the color or albedo of the substances also affect the rate of heat absorption. Students should know that the albedo is the property of reflectivity, or how much light a substance reflects back. Students should be able to know how to use a thermometer and to graph data points.

Explanation: This experiment explains the concept of specific heat and the rate at which different substances absorb and lose heat.

The dark-colored sand and the light-colored sand have the same chemical and physical properties, minus the color of the sand. The dark colored sand has a lower albedo, or reflectivity, and it should absorb more heat than the light-colored sand. Both of these substances have a lower specific heat capacity than water, however, and will heat up at a faster rate than the water. When these substances cool, however, the sands will release heat faster than the water does and will cool at a much faster rate.

Questions & Answers:

1. If we added a fourth substance to this experiment, a Petri dish filled with ethanol, what would you expect the rate of heating to be compared to the other three substances?

A: The ethanol would heat slower than water, but it would heat up faster than the sands because the ethanol has a specific heat capacity that is lower than that of water yet higher than that of the sands.

2. How does albedo explain why having less sea ice and more ocean leads to greater warming of the oceans?

A: Sea ice has a higher albedo than the ocean, which reflects sunlight and keeps the Earth cooler. The oceans have a lower albedo and absorb heat more readily than the ice, so a decreased amount of sea ice and increased ocean would equal more absorption and less reflectivity of heat.

3. The deforestation of rain forests increases the albedo of the region. Explain why this is so, and the effects it would have on the local region.

A: The topsoil that is exposed when deforestation occurs has a higher albedo than the rain forest. The deforested area would reflect more heat, and lower the temperature of the local region. However, the lowered temperature of the deforested area would not counterbalance additional heating produced by the amount of carbon dioxide released from deforestation.

Applications to Everyday Life:

1. The formation of land and sea breezes: the varied rates of heating and cooling of land and water surfaces lead to pressure differences over the land and water. This produces a land breeze or a sea breeze, depending on whether the land surface or the water is more heated.

2. Global climate change: the albedo of a surface determines how much heat that surface will absorb or reflect. Darker land surfaces on Earth, like forests and asphalt, have a lower albedo and absorb heat more readily. Brighter land surfaces like ice will reflect more heat. Altering the terrain of the Earth also alters the albedo of that region, which affects how much heat is being absorbed and reflected by the Earth.

3. Differences in heating rates of different substances: an object with low specific heat capacity requires less heat to reach a given temperature than an object with a high specific heat capacity, and a substance with low heat capacity will cool faster than a substance with high heat capacity. The high heat capacity of water explains why the oceans do not warm or cool as dramatically as land surfaces do.

Photographs: Include a photograph of you or students performing the experiment/demonstration, and a close-up, easy to interpret photograph of the activity --these can be included later.

Videos: Include links to videos posted on the web that relate to your activity. These can be videos you have made or ones others have made.