Question

introduction: boxes of pasta have special instructions for people who live in the mountains. they are told to cook the pasta in boiling water a few minutes longer than normal. question: the altitude of a location is its vertical distance above sea level. how does altitude affect phase changes? 1 form a hypothesis: as altitude increases, the air pressure decreases. how do you think the lower pressure will affect the following? (circle your answers.) a freezing point: increase stay the same decrease b melting point: increase stay the same decrease c boiling point: increase stay the same decrease 2 experiment: use the gizmo to find the freezing, melting, and boiling points of water at 5,000 meters (16,404 feet). write these values below. freezing point: 0°c melting point: 0°c boiling point: 90°c 3 analyze: how did increasing altitude affect the freezing, melting, and boiling points of water? increasing altitude decreases the boiling point of water, while the freezing and melting points remain essentially the same. 4 challenge: try to explain these results based on the fact that air pressure decreases with altitude. if possible, discuss your ideas with your classmates and teacher. pasta takes longer to cook in the mountains because water boils at a lower temperature due to the lower air pressure. 5 apply: why does pasta take longer to cook in the mountains? pressure cookers are useful because they increase the pressure, which raises the boiling point of water, allowing food to cook faster at a higher temperature. 6 apply: a pressure cooker heats liquids at high pressure. why do you think this is useful?

Explanation:

The boiling point of a liquid is affected by air - pressure. As altitude increases, air - pressure decreases. Water boils at a lower temperature in the mountains, which is why pasta takes longer to cook. Pressure cookers increase the pressure, raising the boiling point of water, allowing food to cook faster at a higher temperature.

Answer:

A pressure cooker is useful because it increases the pressure inside, which raises the boiling point of the liquid inside. This allows food to cook faster as it can be heated to a higher temperature than normal boiling water temperature under standard atmospheric pressure. Higher temperature means faster cooking as the rate of heat - transfer and chemical reactions involved in cooking are accelerated.