High School Chemistry : Solids and Liquids
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Example Questions
Example Question #1 : Help With Properties Of Liquids
Which of the following best explains why a chef adds salt to the water when cooking pasta?
The salt lowers the boiling point of the water, allowing the water to cook at a higher temperature
The salt lowers the melting point of the water, making the cooking more efficient
The salt raises the melting point of the water, making the cooking more efficient
The salt raises the boiling point of the water, allowing the water to cook at a higher temperature
The salt raises the boiling point of the water, allowing the water to cook at a higher temperature
Adding salt to water raises its boiling point. This allows the water to get hotter before evaporating. Boiling point elevation is a colligative property. Thus the increase in boiling point is proportional to the number of dissolved particles in solution, not the type of dissolved particles.
Example Question #1 : Help With Properties Of Liquids
If a liquid has a high resistance to flow, it has a high __________.
viscosity
freezing point
solubility
boiling point
None of the answer choices are correct
viscosity
By definition, viscosity is the measure of a liquid's resistance to flow. If a liquid has a high resistance to flow, it has a high viscosity. It may not necessarily have a high boiling point or melting point, nor be easily soluble in other liquids.
Example Question #1 : Help With Properties Of Liquids
Which of the following has the highest vapor pressure?
All of these have the same vapor pressure
Vapor pressure relates to the molecules' ability to escape from their liquid form into a gaseous state. The weaker the intermolecular forces, the greater the vapor pressure (VP). Liquids with hydrogen bonding general have high VP. Bigger and longer molecules have larger VP then smaller ones. Methane does not hydrogen bond, and it is a relatively small molecule, thus many molecules will have enough energy to break the weak intermolecular forces and enter the gaseous phase. Both water and methanol can hydrogen bond. Propane has weak bonds like methane, but it is a larger molecule and will thus have a lower vapor pressure.
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