How Hotwheels Cars Became A Science Project

My 8 yr old son, got some money for Christmas. Last week he decided to spend the remainder of it, and bought some Hotwheels cars. Two of specific importance were color changers. According to the package, they change colors in warm water, and cool water. Neat right? Well not so fast. They changed very easily in the warm water, but when we tried to change them back poof nothing. So of course he was not happy, since he felt like he had been jipped. Me and my natural obsessive self, figured there must be some secret we were not aware of. I visited the official website to see if there were better instructions. Imagine that, there were not any. Matter of fact the commercial clip they have available, clearly shows the cars changing with just a squirt of water. There was no email address, that would be too easy, and the message boards had a few similar questions that of course were unanswered. So I posted the question, on one of the forums I belong to, to see if anyone else had kids with these seemingly useless toys. While I waited for my flood of answers to come in, I continued to think, and wonder what the magic was. I only got 4 responses, 2 were just as curious, and the other two suggested maybe the water was not cold enough. Ah Ha, so we put the car in the freezer for 10 seconds and bingo, it was back to its original color. But wait, it quickly turned back to the warm color. Ok so now we are starting to put two, two together. It is all based on the room temperature as to what color it is. So that if it is warm in the house, the car will change to the warm temperature color, no water really needed. If it is chilly in the house, the car will adapt to the cold color. Of course it would have to be really cold in the house for that to happen. So we got thinking, and experimenting some more. I asked DJ what other things can produce heat, to turn the car to the warm temperature. Of course the first thing he thought was the microwave. While that would be true, that is not what I meant. I told him to think again, about Science and what things naturally produce heat. He said Friction, makes heat. So he began to rub the car with his hands, and bingo it changed to the warm color. Then I told him to put in his armpits, to see what happens. Same result, but the car only changed color partially as the heat was not even across the car. Dj discovered that cupping the car in both hands also worked, as did breathing on it. So you see a simple 3 dollar car, can turn into a Science experiment.