For the second class I used a lab, Molecules in Motion, from the American Chemical Society’s Middle School Chemistry curriculum, which is free on their website. The purpose of todays class was to get across that temperature is related to the kinetic energy (energy of motion) of the molecules and learn how to read a thermometer in Celsius and Fahrenheit. I had a plastic cup of marbles that I jiggled gently and explained that molecules are always in motion and if I heated them up they would move even faster (shake cup vigorously). I then asked the students what they observed about the marbles at ‘higher temperature’ and they quickly answered that they were moving faster and that they were moving higher up in the cup… taking up more space! At which point I explained that’s exactly how a thermometer works. The molecules in the red liquid get hotter, their motion increases and they need more room so it moves up the tube in the thermometer. The Molecules in Motion lab has the students drop 2 drops of food coloring, one yellow and one blue, in both a cup of hot water and a cup of cold water. The students correctly predicted that the colors would mix faster in the hot water.
The food coloring just sank to the bottom of the cold water while the colors mixed fairly quickly in the hot water. Even after a few minutes when the hot water had turned completely green from the mixing colors, the cold water was divided, with blue in one half and yellow in the other half. This was a really nice experiment. We had dropped food coloring in water before but never the two different colors, it really gets the point across.
The second activity was based on a lab we did a few years ago using Science Fusion Module H, Understanding Temperature Scales. The labs for Science Fusion are only available if you have online access. They are not in the books. Anyway its bascially learning how to read a thermometer. The students used thermometers to measure the temperature in Celsius and Fahrenheit of boiling water, warm tap water, room temperature, cold tap water, and ice water. Then they had to graph the temperature in Fahrenheit as a function of the Celsius temperature. This proved a challenge since most of them had not made graphs before – hence the activity. Kids always have a hard time using graph paper and just want to randomly put tick marks on the paper, not realizing they need to make the distance between the tick marks the same or the graph won’t work. Once they had their data plotted I showed them how to draw the best line and they used their graphs to convert from one temperature scale to the next.
So three main ideas today: 1) temperature is related to the motion of the molecules, 2) learned how to read a thermometer and got a feel for Celsius scale, and 3) learned how to make a graph.
For those looking for a fun science textbook for your middleschooler, Ian Guch has started putting chapters of his text, Physical Science: A Smorgasbord of Knowledge, up on his website for FREE. We started reading Ian Guch’s high school chemistry book, Chemistry, the Awesomest Science, last week and my son compared it to Mark Watney from The Martian, but instead of a botanist, he’s a chemist. If you haven’t read The Martian, then shame on you.