Because water has a high heat capacity, which of the...

Because water has a high heat capacity, which of the following statements is true? ? A great deal of energy (heat) is required for water to go from a solid to a liquid. Additional energy is required for water to go from a liquid to a gas. ? A great deal of heat is required for water to go from a liquid to a gas. This is not necessarily true as water goes from a solid to a liquid. ? As water goes from a solid to a liquid and from a liquid to a gas, a great deal of heat energy is given off. ? A great deal of heat energy is required for water to change phase. Due to the nature of the hydrogen bonds, it is impossible to tell in advance whether this energy will be absorbed or given off. ? A great deal of heat is required for water to go from a solid to a liquid. This is not necessarily true as water goes from a liquid to a gas.

Transcript

00:03 Hi there.

00:04 In this question, we have several statements, and we want to know which ones are true about phase changes.

00:10 Well, of course, phase changes refer to changes in state from solid to liquid to gas or the reverse.

00:25 Let's talk for a moment about solid to liquid to gas.

00:28 All of these in this direction require energy.

00:33 So if we're going that direction, they are all endothermic.

00:40 Energy has to be put in.

00:43 From a solid to a liquid is melting.

00:46 From a liquid to a gas is vaporization.

00:49 And vaporization is kind of the umbrella that includes boiling and evaporation.

00:55 Evaporation just means at the surface while boiling means vaporization through the entire substance.

01:01 We can also go directly from a solid to a gas, and that is referred to.

01:05 To as sublimation.

01:09 All right, we can also go the other direction.

01:14 When we are going the other direction here, energy is given off.

01:20 So those are all exothermic processes.

01:24 A gas to a liquid is, of course, called condensation.

01:27 Liquid to solid is freezing, and gas to solid, going directly from a gas to a solid, is deposition.

01:35 Okay, i think we have a little bit of an overview here.

01:38 I will want to number these statements so that we know which one we're talking about.

01:43 I see there are seven of them there.

01:45 So i'm just going to give them numbers one through seven.

01:50 And we are looking for the true statements.

01:53 All right.

01:53 The first one says a substance phase depends upon its temperature and its pressure.

01:59 And that is definitely true.

02:03 We know temperature is important, but pressure is also important.

02:07 You can take a gas at a high temperature, but by putting it under a lot of pressure, you can push those molecules close enough together that it liquefies.

02:18 So definitely true.

02:20 All right.

02:20 The next one says, boiling water is an example of an exothermic process.

02:26 Well, that is false because boiling water means we're taking it from the liquid to the gas.

02:32 We have to put energy into it.

02:34 So that one's false.

02:37 Let's look at the next one.

02:38 The next one says water is an uncommon example of a substance with a liquid phase more dense than its solid phase.

02:47 That is true.

02:49 If we think about putting ice cubes in water, we know what the ice cubes do in water...

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