Fig 7. The graph shows the melting and boiling points of water.
Melting point The temperature at which a substance changes from a solid state to a liquid state.
The part of the graph labelled A is where the substance is melting. This is the latent heat of melting. This temperature is called the melting point. The part of the graph labelled B is where the substance turns to a gas. This is the latent heat of evaporation. This temperature is called the boiling point.
Melting point The melting point of a substance is the temperature at which it changes from being in a solid state to being in a liquid state. The melting point of water is 0o
C.
Activity To measure the melting point of chocolate.
Apparatus Beaker, Bunsen burner, tripod, gauze, boiling tube, thermometer, a few squares of chocolate
Method 1. Half fill a medium beaker with water. 2. Break up some chocolate and put the pieces into a boiling tube.
3. Put a thermometer into the boiling tube and place it in the beaker of water as shown in Fig. 8.
4. Heat the water gradually. 5. Stir the chocolate continuously and record the temperature of the chocolate every 15 seconds for five minutes.
