Chapter 17, Problem 13TE

What physical and chemical changes occur when a wax candle burns?

To determine

The physical and chemical changes that occur when a wax candle burns.

Answer to Problem 13TE

The melting of wax and freezing again is a physical change while the burning of candles is a chemical change.

Explanation of Solution

The transformations of matter are of two types. The types are physical change and chemical change.

The physical change includes the change of states of matter. A chemical change occurs when two or more substances combine to form new and different substances.

There are three states of matter. The states are solid, liquid, and gas. The different states are due to the difference in the movement of molecules that are present in matter.

The states change when the heat is applied or removed.

When a wax candle is burnt, the wax melts due to the heat and after moving away from the heat it freezes. In this, the state changes are taking place from solid to liquid and from liquid to solid. It is a reversible change. So, it is a physical change.

When the wick with wax burns, it combines with oxygen molecules and form new substances which are carbon dioxide and soot. The carbon dioxide can be seen as smoke. As new substances are formed, it is a chemical change.

Conclusion:

The melting of wax and freezing again is a physical change while the burning of candles is a chemical change.