Calculate the amount of heat required to convert 80.0 g of ice at -15.0^∘ C to steam at 125.0^∘

Name: Problem 50, Chapter 13: Chemistry
Uploaded: 2021-07-05T10:59:41-08:00
Duration: 9 min 37 s
Channel: Adriano Chikande
Description: Calculate the amount of heat required to convert 80.0 g of ice at -15.0^∘ C to steam at 125.0^∘ C

Calculate the amount of heat required to convert 80.0 g of...

Key Concepts

Calorimetry

Calorimetry is the experimental measurement of the amount of heat released or absorbed during a chemical or physical process. It involves summing the energy required for temperature changes (using specific heat capacity) and the energy involved in phase transitions (using latent heats) to determine the total heat transfer.

Phase Change Processes

Phase change processes involve a substance undergoing a transition between different states of matter (solid, liquid, gas). During these transitions, energy is absorbed or released without a change in temperature, and calculations must account for both the latent heat involved and any temperature changes before or after the transition.

Specific Heat Capacity

This refers to the amount of heat energy required to raise the temperature of a unit mass of a substance by one degree Celsius (or Kelvin). It is a fundamental property that varies for different states of matter such as solids, liquids, and gases, and is used to calculate the heat needed to change the temperature of a substance without a phase change.

Latent Heat of Fusion

This is the amount of heat energy required to change a substance from solid to liquid at its melting point without changing its temperature. It is crucial for calculations involving the phase transition from ice to water, reflecting energy absorbed during melting.

Latent Heat of Vaporization

This represents the heat energy required to convert a substance from liquid to gas at its boiling point while the temperature remains constant. It is a key concept for processes involving evaporation or boiling, such as converting water into steam.

Transcript

00:01 This question is looking at a temperature change of ice from negative 15 degrees celsius right up to 125 degrees celsius.

00:09 So the first thing that we have to assume is that all of this, the temperature change is occurring at constant pressure.

00:18 And we are going to assume that this is this constant pressure is one atmosphere.

00:23 That is all of this is going to be happening at atmospheric temperature.

00:28 So there are certain things that we have to appreciate, like at negative 15 degrees celsius, this is ice, so it is solid h2o.

00:37 The h2o will be in the solid state, but at 125 degrees celsius, this is going to be vapor, that is a glacier state.

00:47 We are assuming that all of this is occurring at atmospheric pressure.

00:51 So we know that there are certain important temperatures like 0 degrees celsius, which is the milton point of h2o, at one atmosphere you also know that the boiling point h2o the boiling point of h2o at one atmosphere is 100 degrees celsius so we're assuming that the temperature is gradually increased so as it is moved from negative 1 5 degrees celsius it will melt then you're going to be having a liquid and then vaporize at 100 degrees celsius and then move on to 125 degrees so the movement from 100 degrees celsius to 125 degrees celsius, this will be a vapor.

01:37 We're increasing the temperature of a vapor and the movement from 0 to 100 degrees celsius we're increasing the temperature of a liquid.

01:47 And then from negative 1, 5 to 0 degrees celsius, this will be a solid that starts melting at 0 degree celsius.

01:55 So if we are to look at the phase diagram, putting what we've just described above, let's say this is temperature in degrees celsius and this is the heat input.

02:12 So we're going to start at negative 15 degrees celsius and the temperature is going to increase right up to 0 degrees celsius.

02:23 Zero degrees celsius and it will start melting.

02:27 Remember the change of phase or cares at constant temperature.

02:35 So it will start melting.

02:37 0 degrees celsius and all of it is going to melt at a constant temperature so after melting we're going to increase the temperature is going to increase again right up to now we've got a liquid here this is a liquid this is a solid so this is what melting then the temperature will increase again right up to a hundred degrees celsius where it will start evaporating or boiling or changing phase into gaseousias phase so and then after this, it will also then increase right up to the final temperature, the target temperature of 125 degrees celsius.

03:17 So the heat input, we've got changes 1, 2, 3, 4 and 5.

03:29 So this is what is going to be happening.

03:33 This is what is going to be happening.

03:36 So the heat changes, the heat change from negative 5 to 1.

03:42 125 is going to be the sum of the heat energy changes that are going to be occurring at each stage from stage 1 up to stage number 5.

03:54 So we know that the heat generally is equal to the mass multiplied by the specific heat capacity multiplied by the change in temperature.

04:06 We also know that at phase change, the heat input is going to be equal to the mass multiplied by the change.

04:13 By the heat of fusion or vaporization.

04:22 Where the heat of fusion is the heat that is required to change phase from solid to liquid...

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