Is burning a candle a physical or chemical change? This was the question on everyone's mind as they played with fire.
In groups of three, we had to balance a candle between two cups or glasses. We had to measure and find the halfway point on the candle, poke a nail on each side - directly opposite each other to create a pivot point and balance the nails on the cups. We used paperclips to make sure the candle did not fall off the cups.
We lit both ends of the candle and stood back to observe what happened.
Most of us predicted that the candle would stay still and the wax would melt. One or two of us thought that it might move.
The result was that most candles rocked or see sawed back and forth as the wax melted on one end (the end that was facing downwards), making that end of the candle lighter and so it rose to the top. That meant that the other end was now dripping wax on the tin foil and so that end became lighter and rose to the top.
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A physical change is when something changes but can be changed back into its original state and no new substance is made. A chemical change is when a new substance is formed and you cannot reverse it. When we discussed the experiment and asked the questions about physical and chemical change we decided that the wax melting was a physical change that caused the movement of the candle. Most of the wax was on the tin foil in a different shape. The wick burning was a chemical change as it couldn't be returned to its original state.