Mr. Keith lights a pine tree-scented candle in his office before grading his students’ CRQs. While the candle wick burns, some of the wax melts and starts to drip down the side of the candle, hardening at the base, some of the wax "reacts/disappears" as rising smoke. Identify ALL the chemical and physical changes that are occurring.

the wax hardening at the base is a physical change while the wax that disappears or react is an example of chemical change

Explanation:When a candle burns, both physical & chemical changes occur.

Physical Changes in Burning Candle: when heating a candle, the candle wax melts and form liquid wax. This process is a physical change. Since it again turns into solid wax on cooling. This is a reversible change.

Chemical Changes in Burning Candle: When you light the candle, the wax present near the wick will melt into liquid wax then the wick absorbs the liquid wax. The liquid wax absorbed by the wick is vaporized because of the heat produced by the flame. This wax vapor near the flame then burns and then gives new substances like Carbon Dioxide, Carbon soot, water vapor which is an irreversible change.

A)The students could repeat the experiment using different candles; there might have been a flaw in the candle.

Explanation:

work: w = fd (given)

work done by chet   =50*1 = 50 j

work done by mika =40*2 = 80 j

work done by sara =30*1.5 = 45 j

work done by bill =60*0.5 = 30 j

students in order from the greatest amount of work done to the least is mika> chet> sara> bill

hence option (b) is correct.

a and b sometimes have a positive value