when water and ice are mixed the temperature of the mixture is 0 degrees Celsius. When methyl alcohol and ice are mixed a temperature of -10 degrees is obtained. Why is there such a difference?
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The difference in temperature between mixing water and ice versus methyl alcohol and ice can be explained by the concept of freezing point depression.
Freezing point depression occurs when a solute (such as alcohol) is added to a solvent (such as water), which decreases the freezing point of the solvent. In simple terms, when a solute is added to a solvent, it disrupts the formation of a solid lattice structure, inhibiting the crystallization process and lowering the freezing point of the solvent.
In the case of water and ice, the freezing point of pure water is 0 degrees Celsius. When they are mixed, the temperature of the mixture will stabilize at the freezing point of water, which is 0 degrees Celsius. This is because water and ice are chemically similar substances, so there is no significant change in the freezing point.
On the other hand, when methyl alcohol (also known as methanol) is mixed with ice, its presence interferes with the formation of ice crystals, causing the freezing point of methyl alcohol to be lower than that of water. The freezing point of pure methyl alcohol is around -97 degrees Celsius. When ice and methyl alcohol are mixed, the temperature of the mixture will depend on the concentration of the alcohol, but it will be significantly lower than 0 degrees Celsius. In this case, the liquid methyl alcohol prevents the mixture from freezing until it reaches a temperature of -10 degrees Celsius.
Therefore, the difference in temperature between mixing water and ice versus methyl alcohol and ice is due to the different freezing point depressions caused by the solutes (water in water-ice mixture and methyl alcohol in alcohol-ice mixture) disrupting the crystallization process.