A voltmeter is a device that measures electricity. It can detect the amount of electricity between two electrodes when they are submerged in a solution, such as salt water. Describe how you would find the melting point and the conductivity of the white substances in the beakers. Then, explain how you could identify which substance is salt and which is sugar.

Explanation:

To determine the melting point of the unknown white substances. A sample of each of the unknown can be placed in separate capillary tubes and then placed in an adjustable heat source (for example water bath). A thermometer is then placed in the heat source very close to the tube holding the sample. The temperature of the heat source will be adjusted until the solid substance in the capillary tube starts to melt, the temperature at this point is noted as the melting point.

To determine the conductivity of the white substances, an electrolysis experiment is done. A sample each of the unknown substances is dissolved in water. These aqueous solutions are prepared separately. Two electrodes (positively charged anode and negatively charged cathode) are dipped into each of these solutions and an electric current is passed through these solutions, from an energy source (such as batter), through the electrodes (with the electric current flowing from the anode to the cathode). A voltmeter is then connected to this set-up to determine if electricity is been passed through the individual solutions.

The substance that is the salt will be the white substance that has the higher melting point and conducted electricity in the electrolysis set up; this is because NaCl salt is an ionic compound which has a high melting point and conducts electricity when dissolved in water. While the white substance that had a lower melting point and did not conduct electricity will be the sugar; this is because sugar/sucrose is an organic substance that has a low melting point and does not conduct electricity when dissolved in water.