Week 4 HEAT TRANSFER

The question for this guided inquiry was, “What material would make the best insulator for 250 ml. of hot water; cotton cloth, foil, glass or plastic?” I thought about the materials that I wanted to test, in hopes to find the best method to keep drinks, such as coffee, hot.  I hypothesized that the glass covering would be the best insulator of the hot water. The manipulated (independent) variable for this experiment were the different materials used to cover the mug of hot water. I chose cotton cloth, foil, a glass plate and a Ziplock baggie. The responding (dependent) variable was the temperature of the water after 30 minutes.  The controlled variables for this experiment include; identical mugs, the amount of water, the beginning temperature of the water and using the same thermometer. The data I collected is listed in the following table. The beginning temperature of the water was 66⁰ Celsius.

Temperature of water after 30 minutes

Material	Trial 1	Trial 2	Trial 3
Cotton cloth	47⁰ C	46⁰ C	47⁰ C
Foil	46⁰ C	46⁰ C	45⁰ C
Glass	44⁰ C	43⁰ C	42⁰C
Plastic	48⁰ C	49⁰ C	49⁰ C

Four identical mugs with the material coverings of cloth, foil, glass and plastic

 In conclusion, I learned that plastic is a better insulator than foil, cotton cloth or glass. My hypothesis was incorrect. I thought that the foil would be a good insulator because it has similar properties that metals have. Metal is a better conductor of heat and transfers heat energy quickly. However, I learned most insulating materials are good insulators because they contain many small air spaces. The small air spaces are poor conductors because the molecules of air are far apart, compared to a solid, making it more difficult to pass the increased vibrating motion from molecule to molecule. (Tillery, Enger & Ross, 2008)  Conductors do transfer heat but do not make the best insulators.

The challenge that I experienced was with the thermometer that was supplied in the science kit. I used it to measure that temperature of the water after it was heated on the stove. I measured 250 ml. into a measuring cup and put the thermometer in, and the glass bulb burst open within seconds. I had to go to my school and get a new thermometer that measured temperatures at a higher level and then restart the experiment.

The plastic material was the best insulator.

I will incorporate this guided inquiry with my students in place of the experiment that I already perform. I will have the students use beakers instead of mugs. It works better to cover the liquid, instead of wrapping the materials around the test tube, as I currently do.  The cotton that I have my students place in the opening of the test tube always seemed to fall in the water.