What is the Best Insulator: Air, Styrofoam, Foil or Cotton?
3 That heat flows from hot to cold is an unavoidable truth of life. People have put a lot of effort into stopping this natural physical behavior, however all they have been able to do is slow the process. Student teams investigate the properties of insulators in their attempts to keep cups of water from freezing, and once frozen, to keep them from melting. Temperature regulation is important in many aspects of engineering. Packaging engineers design containers and systems to be able to reliably ship items at specific temperatures. Mechanical engineers make sure that working engines do not overheat, and electrical and computer engineers design electronics so that they do not overheat. Civil engineers must specify the most suitable insulating materials for the climate where their structures reside. Temperature regulation applies an understanding of the principles of heat transfer, which is relevant in almost all engineering disciplines. conductor energy freeze heat transfer insulator melt temperature regulation What "insulate" means and its implications in keeping things cold or warm. Basic experimental processes. How natural materials differ from human-made materials in terms of insulation. 4 3 oz. plastic cups per group 4 larger clear plastic cups per group warm water in a pitcher insulating materials (3 Styrofoam cups per group, 1- 8 ½" x 11" piece of aluminum foil per group, 20 cotton balls per group) 4 rubber bands per group plastic wrap baking pan large book or magazine Data Chart (to be filled in during the experiment) Results Chart (to be filled in after the experiment) When you go to a summer picnic or the beach or at the lake, why do you put your cold drinks and ice in a cooler? What would happen if you put them in a backpack instead? (Listen to student ideas.) Yes, that's right, you would end up with a wet backpack and warm drinks. The cooler helps to keep the drinks cold because it acts as an insulator and slows the transfer of energy from one source to another, meaning it helps keeps the inside of the cooler cold and the heat out. The opposite of an insulator is a conductor. What do you think a conductor does? (Listen to student ideas.) Yes, that's right, a conductor speeds up the transfer of energy from one source to another. You may have experienced this if you ever removed the cover of a pot cooking on the stove. A metal pot is a conductor and heats up quickly on the stove so that it cooks food or boils water faster. Just be careful before touching a metal pot because you could get burned. What would happen if you designed a cooler using a material that acts as a conductor? Or a cooking pot with a material that acts as an insulator? (Listen to student ideas.) To prevent or slow the transfer of electricity, heat, or sound from one environment to another. A substance or body that can allow electricity, heat, or sound to pass through it. A substance that resists the flow of heat, electricity, or sound through it. A form of energy that causes substances to rise in temperature or to go through associated changes (melting, evaporation, or expansion). The capacity for doing work. Energy can be in many forms such as electrical, mechanical, chemical, sound, light, and heat. A principle in physics which states that energy can neither be created nor destroyed and that the total energy of a system by itself remains constant. The process of changing from a solid to a liquid state through heat gain. The process of changing from a liquid to a solid (as ice) by loss of heat. Insulation helps keep cold things from warming up and warm things from cooling down. Insulators do this by slowing down the loss of heat from warm things and the gaining of heat by cool things. Plastics and rubber are usually good insulators. It is for this reason that electrical wires are coated to make them more safe to handle. Metals, on the other hand, usually make good conductors. In fact, copper is used in most electrical wires and circuit boards for this reason. Recommended Resources: Phase changes and phase diagrams: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/phase.html Forms of energy description (grade 4): http://www.nyu.edu/pages/mathmol/textbook/energy.html Gather materials and make copies of the attached Data Chart and Results Chart files. To minimize the time spent in the classroom for this activity, prepare the insulating materials (although students CAN do this!!). Break up the foam cup into small pieces. Tear the aluminum foil into pieces and loosely crunch up the pieces. Pull the cotton balls apart a little and flatten them so that they resemble pancakes. Discuss with your students what types of devices they have seen or used to keep things both warm or cold. Talk about the materials from which they think these devices are made. Have students examine the insulators they are going to be given and have the groups make predictions about which will work best. Divide the class into groups of two to four students each. Hand out materials and blank chart handouts to each group. Each group gets four different insulators: air, Styrofoam, aluminum foil, and cotton balls. Have students place enough of each insulating material in each large plastic cup so that it covers the bottom of the cup. Do not put anything in one of the large cups because air will be the insulator for that cup. Place a small 3 oz. cup in the center of each large cup. Have students fill the space between the cups with the same insulating material they used on the bottom. Place 3 teaspoons of warm tap water in each small cup. Have each group cover all of their large cups with plastic wrap held on by a rubber band. Place the cups in the freezer. Check the cups every 15 minutes to see which cup forms ice first. Keep checking until you see ice form in all four cups, and record observations on the chart. Allow the cups to sit in the freezer until the ice is frozen solid in all of the cups. Take the cups out of the freezer and place in a baking pan. Place a book or a magazine on top of the cups to keep them from tipping or floating. Pour very warm tap water into the pan. Have the teams check their cups every few minutes to see which seems to be melting first, second, third and fourth. Conclude with a class discussion to compare results and findings. Use the attached Rubric for Performance Assessment to gauge student accomplishments in terms of the experimental process and teamwork. Data Chart (doc) Data Chart (pdf) Results Chart (doc) Results Chart (pdf) What does "insulate" mean? What materials are used for insulation? Which insulator was best at slowing down the loss of heat from the warm water? Which was the worst? Did the results in the second half of the activity make sense with the results from the first half? Is Styrofoam, foil, or cotton better for insulating a cup of ice? Rubric for Performance Assessment (doc) Rubric for Performance Assessment (pdf) For students to experience first hand that foil is not a good insulator, follow-up the activity with this quick hands-on demonstration: Have students wrap a cup with aluminum foil and another cup with paper. Pour ice water into the cups. Have students hold the cups in their hands to judge which material is the best insulator. Kessler, James H. and Andrea Bennett. The Best of WonderScience: elementary science activities. Boston: Delmar Publishers, 1997. p 207, 210-211 ISBN: 0827380941