posted by minka .
okay i have a question which is on a key assesed piece
explain the physical and chemical changes when a candle burns using the big idea of energy?
what is the big idea of energy?
This is something I'd be interested in as well. What presicely energy is isn't clear so far. Scientists are argueing about this. So your science teacher is asking a rather ridiculous question, you can tell that.
However, the idea supposed to be used here is the concept of heat being a form of energy, i.e. the spoken-of energy, namely the heat, causes a chemical reaction so-to-speak: It breaks up the bondings between the molecules of the candles, i.e. the candle (the wax) turns liquid. Hence the liquid wax runs down the candle as it's got a bigger volme becaus of simply being liquid. Consequently, the candle's shape changes as the wax afterwards chills down again. The little wool thread in the candle turns black because the evoloving molecule causing this color is combined from carbo and dioxyde and other elements such as hydrogen. But it is not necessarily carbondioxyde which emerges and causes the coloring.
Thank you dongo you have made my life so much easier