Solar Heating & Retention Science Experiment

Gather your materials. Collect roughly 1 cup of each material listed below, and place each item separately into its own individual Ziploc bag. Note: Each material will get its own clear, sealable bag.

• Gravel/rock
• Wood chips or mulch
• Leaves
• Dirt
• Sand
• Grass cuttings

Note: Feel free to add any materials to this list! Look around your backyard and see if there are any other items you would like to add to this experiment.

Next, label and seal each bag for the data collection process.

Note: Make sure you do not block the sun’s light with a label. For example: label the item at the bottom corner of the bag or at the top where the bag zips.

Create the data collection chart. Using your science notebook or a sheet of paper, create a chart that includes: each material and the outside temperature for both the sun and the shade portions of the experiment in four (4) increments – 30 minutes, 60 minutes, 90 minutes, 120 minutes.

See chart below for reference:

Prep the experiment location. Find a sunny location outside with direct sunlight. Be sure that trees, building, or other tall objects will not block the sunlight for a two (2) hour period. The location must get at least 2 hours of full sun. Place each plastic bag of materials on a white piece of paper (printer or construction paper), leaving about on (1) inch of space between each bag. Finally, select a location where there will be 2 hours of shade for the second part of the experiment.

Note: The bags are placed on a piece of white construction paper so that only the materials in the bag will absorb the sun’s heat. If the surface below the materials were a dark color, it could skew the internal temperature of each item because dark colors absorb more light energy (heat).

Collect data! The experiment is broken down into two (2) separate data collection locations: a sunny spot and a shaded spot.

Every 30 minutes for 2 hours (120 minutes), take both the temperature outside, as well as the internal temperature of each bag of materials. To do this:

1. Use an outdoor thermometer or a weather app to record the temperature outside, and record the information on the chart.
2. Use the cooking thermometer to gather the internal temperature of each material and record the data on the chart. Note: you will need to unzip the bags slightly to complete this step. If you find condensation is an issue, leave the bags open during the experiment.
3. Continue to take readings for both the outside temperature and the internal temperature of each bag of material every 30 minutes for two (2) hours.
4. While collecting the data, try to find patterns and make observations about each material and the outside temperature.

After two (2) hours of recording the temperatures in the sun, move the bags and white paper to a completely shaded area. Then, move onto the data collection in the second location (in the shade), by completing the following tasks:

1. Use an outdoor thermometer or a weather app to record the temperature outside and record the information on the chart
2. Use the cooking thermometer to gather the internal temperature of each material and record the data on the chart.
3. Continue to take readings every 30 minutes for 2 hours.
4. While collecting the data, try to find patterns and make observations about each material.

Take a look at the data. Find patterns and other observations about each material and the temperature in both the sun and shade. Do this before moving to the “Results/Review” section.

Before diving into the data and analyzing the temperatures, it is important to state that the below data was recorded during peak sun hours (12pm-4pm) and also during a hot and sunny month of summer. With this information stated, take a look at the patterns and trends.

Trend 1: During the portion of the experiment when the materials were in the direct sunlight, most of the materials reached an internal temperature between 130 to 140 degrees Fahrenheit when the outdoor temperature increased. The two outliers of the experiment were: 1) the dark colored wood chips that reached an internal temperature of 145 degrees on the high end, and 2) the sand with 130.4 degrees on the lower end.

Trend 2: The leaves and grass seemed to mimic each other rather closely during both the sun exposure (absorption) and the shaded section (retention) part of the experiment. The leaves reached an internal temperature of 136.5 degrees while the grass reached an internal temperature of 139.1 degrees. The slight variation may have been due to the clumps of soil that remained with the grass roots. During the retention section of the experiment (shade), both the grass and leaves lost their overall thermal heat quickly and remained around 83 degrees after 2 hours.

Trend 3: The dark materials (wood chips and dirt) absorbed the most heat during the experiment which makes complete scientific sense! Darker colored objects absorb more light, which in turn creates a higher internal temperature.

Trend 4: The sand absorbed the least amount of heat through passive solar heating and also lost the solar heat energy the fastest when placed in the shade. This was due to the light coloring of the sand and the heat capacity of the material (which will be discussed in the next section).

Trend 5: All of the materials retained just a small amount of the solar heat obtained during the sunlight absorption section. In fact, all the materials quickly lost heat and seemed to level out at about the same temperature after 2 hours of no sun.