Why does baking soda lower the freezing temperature of water?

Baking soda does not lower the freezing temperature of water. In fact, it raises the freezing temperature of water by depressing the freezing point. To understand this, we can look at the colligative properties of solutions.

Colligative properties are properties of solutions that depend on the concentration of solute particles, regardless of the identity of the solute. One of these colligative properties is freezing point depression. This means that the freezing point of a solution is lower than the freezing point of the pure solvent. The more solute particles there are in a solution, the greater the freezing point depression.

Baking soda (sodium bicarbonate) is a solute that dissociates into ions when dissolved in water. This means that each molecule of baking soda produces two ions, one sodium ion (Na+) and one bicarbonate ion (HCO3-). These ions interfere with the formation of ice crystals, which raises the freezing point of water.

The extent to which baking soda raises the freezing point of water depends on the concentration of the solution. A more concentrated solution of baking soda will raise the freezing point of water more than a less concentrated solution.

In general, adding any solute to water will raise the freezing point of water. This is why salt is used to melt ice on roads and sidewalks. The salt dissolves in the water on the road, creating a solution with a lower freezing point. This means that the water can remain liquid at a lower temperature, which helps to melt the ice.

However, it's important to note that there is a limit to how much the freezing point of water can be raised. If too much solute is added to water, the solution will become so concentrated that it will actually start to lower the freezing point of the water. This phenomenon is called the "eutectic point."