Freezing Point

This is the setup for freezing of water. Before freezing, the water is in its liquid state. Let's look closely at thermometer. The temperature of the water is 21 degrees Celsius. Let's put this on a graph. To freeze the water in the test tube, let'surround the test tube with a beaker of ice and salt. The water in the test tube is losing heat to the beaker of ice. The temperature of the water in the test tube is dropping below 20 degrees Celsius. Let's look at the graph. The water in the test tube continues to lose heat, and this causes the temperature to decrease. The temperature of the water in the test tube is dropping below 10 degrees Celsius. Let's look at the graph. The graph is showing a downward trend. The water in the test tube continues to lose heat to the beaker of ice. Now, the temperature is 0 degrees Celsius. As the water continues to freeze, the temperature remains constant at 0 degrees Celsius. This is known as the freezing point. Let's look at the graph. Look, the water in the test tube has changed its state from liquid to solid. What have we learnt? When water freezes, it changes its state from liquid to solid. The temperature remains at 0 degrees Celsius during freezing. This is known as freezing point.