a. A physical change is the change of form or appearance of a substance. It's composition or identity does not change.
b. A chemical change occurs when a substance changes into one or more new substance.Burning Out A Candle:
The first experiment we did was blow out the fire on the candle with gas. We created a gas by adding baking soda to vinegar and putting it close enough to the flame to diminish any oxygen from the flame, causing it to burn out. The first time, we messed up putting too much of each which overflowed and touched the candle, forcing us to do to again. But in the end, we created a gas which just by placing near the flame, will burn out. This is a physical change because the fire was burned out by the gas, which is a change of form/appearance of the substance. (Not so sure, but I think it could be a chemical change because after burning it it created a charred substance.)
Roasting A Marshmallow:
The second experiment we roasted a marshmallow on a bunsen burner. We burnt one part of it, leaving it charred, and the rest was a golden brown (so gooey on the inside). We tasted the charred part, and to it tasted really bad (like solid smoke) but the golden brown was not roasted too much and tasted very good. This is a chemical change because we burnt the marshmallow with fire, causing the charred area to appear, creating another substance.Burning Sugar:
We placed sugar into a test tube to burn it. We placed it above the bunsen burner. The color changed very quickly, from white, to carmel, to black. After a while a huge puff of yellow smoke came out of it so we took it down. As Mrs. Rousseau broke the glass, we had to observe it. It looked like black honey, it was dark and smooth and hot. It was also partially gooey. We did not get a good chance to feel it first so we tried to take the glass off of it (causing me to get glass in my finger), and got a better feel of it.