When matter changes from one physical state (solid, liquid, gas, or plasma) to a different physical state, a phase change is defined to have occurred.

When a solid changes to a gas, the phase change that occurred is defined as sublimation:

Solid  Gas

When the opposite occurs and a gas changes to a solid, the phase change is defined as deposition:

Gas  Solid

When a liquid changes to a gas, the phase change that occurred is defined as vaporization. It is worth noting that there are two types of vaporization: evaporation (when the phase change occurs below the boiling point for the substance) and boiling (when the phase change occurs at or above the substance's boiling point).

Liquid  Gas

When the opposite occurs and a gas changes to a liquid, the phase change is defined as condensation:

Gas  Liquid

When a liquid changes to a solid, the phase change that occurred is defined as freezing:

Liquid  Solid

When the opposite occurs and a solid changes to a liquid, the phase change is defined as melting:

Solid  Liquid

When a gas changes to a plasma, the phase change that occurred is defined as ionization:

Gas  Plasma

When the opposite occurs and a plasma changes to a gas, the phase change that occurred is defined as recombination.

Plasma  Gas

Some may find it easiest to remember the phase changes by memorizing them in pairs. For example freezing and melting both refer to phase changes between solids and liquids. Once that is memorized, the possible phase changes that you have to choose from is reduced from 8 to 2. Also, it may be helpful to think that all the phase changes involving a decrease in entropy (increase in order) deposition, condensation, freezing, and recombination sound like more orderly words than the phase changes involving an increase in entropy (decrease in order) sublimation, vaporization, melting and ionization.

This question is asking us about the effect that elevation has on the boiling point of water. In order to answer this, we need to have a fundamental understanding of what boiling is, and how it can be affected by factors such as elevation.

Boiling is a type of phase transition in which a liquid is converted into a gas. During this transition, the boiling point is defined as the temperature at which the vapor pressure of the liquid is exactly equal to the atmospheric pressure. Therefore, if the atmospheric pressure is lowered, which happens at increased elevations, then it becomes easier for the liquid to evaporate into the gas phase. Consequently, less energy (and a lower temperature) is needed to push the liquid into the gas phase. As a result, the boiling point of the solution is lowered at increased elevations.

The equation for boiling point elevation is .

Since all of the solutions are aqueous, we do not need to consider the boiling point elevation constant () when comparing the solutions. The two factors we need to consider are molality () and the van't Hoff factor () of the solute.

Glucose will not ionize in solution, sodium chloride will make two ions in solution, and magnesium chloride will make three ions in solution.

When multiplying the molality by the van't Hoff factor, we can determine that the magnesium chloride solution will elevate the boiling point by the highest number.

Since the glucose is nonvolatile, we can use the boiling point elevation equation to solve for the new boiling point.

Since glucose does not ionize in water, the van't Hoff factor is simply 1 for this problem. The molality can be found by the moles of solute per kilogram of solvent.

This means that the boiling point for the water will be elevated by 1.03^oC with the addition of the glucose. Since pure water has a boiling point of 100^oC, the boiling point for this solution is 101.03^oC.

The correct answer choice is the equation for boiling point elevation when solute is added to a solvent.

In order to solve for the molar mass of the unknown compound, we need to use the freezing point depression equation.

Since molality is equal to the moles of solute divided by the kilograms of solvent, we can substitute the moles of solute with the mass of the solute divided by the molar mass of the solute.

This allows us to solve for the molar mass of the compound using a substituted equation.

We can use the values given in the question to solve for the molar mass.

First, we need to calculate the molality because that is what we use in our equation for freezing point depression. We can get that from the molarity without knowing exactly how many liters or grams we have. We just have to know what we have one mole per liter. The weight of water is one kilogram per liter, so this allows us to make this conversion.

The molality is 2m. The van't Hoff factor is 3, as we get one calcium ion and two chloride ions per molecule during dissociation.

We can now plug the values into the equation for freezing point depression.

This gives us our depression of .  The normal freezing point of pure water is , which means our new freezing point is .

The important thing to remember for this question is that it doesn't matter what the solutes are in freezing point depression, just how many ions are created during dissociation. First, we need to convert our solute amounts to moles.

The molality of the solution is the moles of solute per kilogram of solvent. Since water has a density of one kilogram per liter, we can simply divide the total moles by the liters of solution. The molality of the solution is .

We can treat this solution as 3L of water containing 4mol of a solute that dissolves into a total of 5 ions. It does not matter which compound the ions come from, only that they end up in solution in the correct proportion. 2mol of calcium chloride will contribute 3 ions per molecule and 2mol of sodium chloride will contribute 2 ions per molecule, for a total of 5 ions per mole of solution.

Using these conclusions, we can solve the freezing point depression.

Our depression is then . Since the freezing point of pure water is , our new temperature for freezing point is .

For reference, the freeing point depression equation is:

Since we want to triple the melting point change, we need to manipulate the freezing point depression equation so that the value of  is three times as large.

Replacing glucose with magnesium chloride will make the van't Hoff factor three, so the melting point change will triple.

Reducing the amount of water by a factor of three will also triple the melting point change, as will tripling the glucose amount.

Six moles of sodium chloride will triple the solute concentration and make the van't Hoff factor two. This multiplies the melting point change by six.

When a solid is dissolved into a liquid, in our case water (snow), the freezing point will decrease. This phenomenon is called freezing point depression. In order to freeze, the molecules of the liquid must organize into a relatively static lattice. This highly organized structure is disrupted by the presence of extra molecules and ions that are dissolved in the liquid, making it harder to transition to a solid.

With enough salt in the snow, the freezing point will depress below the current temperature, leading the snow to melt and be in the liquid phase. The salt ions will infiltrate the ice/snow lattice, breaking apart the solid and cause the water to remain liquid.