Physics 22 Introduction to Heat & Temperature (6 of 6) Change of Phase & Latent Heat
Summary
TLDRThis script delves into the concept of phase changes in thermodynamics, focusing on the latent heat associated with these transitions. It illustrates the process using the example of water, explaining how much heat is required to melt one gram of ice or to evaporate one gram of boiling water. The script clarifies the difference between latent heat of fusion (80 calories per gram for ice to water) and latent heat of vaporization (540 calories per gram for water to vapor), emphasizing the significant energy involved in phase changes without a change in temperature.
Takeaways
- 🔍 The topic of discussion is the change of phase in materials and associated latent heat in thermodynamics.
- 🧊 Discussing the example of adding one calorie of heat to one gram of water, which is expected to increase the temperature by one degree Celsius.
- ❄️ When one gram of ice at zero degrees Celsius is heated, it begins to melt, and a significant amount of heat is required to completely melt it.
- 🔥 The transition from solid to liquid or liquid to gas requires energy, which is referred to as latent heat.
- 🔑 The phase change from solid to liquid requires breaking the bonds that lock atoms in position, allowing molecules to vibrate and eventually roll over each other.
- 🌡️ It takes 80 calories to completely melt one gram of ice at zero degrees Celsius, which is 80 times more than raising the temperature of water by one degree Celsius.
- 💧 To evaporate one gram of boiling water at 100 degrees Celsius, 540 calories are required, indicating the large amount of energy needed for phase change.
- ⚖️ The equation for phase change heat is Q = M * L, where Q is the heat added, M is the mass, and L is the latent heat of the material.
- 🔄 The latent heat of fusion is the energy required to change from solid to liquid, and the latent heat of vaporization is for changing from liquid to gas.
- 📏 The units for latent heat are energy per gram or energy per mass, with the grams canceling out, leaving calories as the unit.
- 🌟 The concepts of latent heat of fusion and latent heat of vaporization are applicable to all substances, not just water.
Q & A
What is the main topic discussed in the script?
-The main topic discussed in the script is the change of phase of materials and the associated latent heat in thermodynamics.
What happens when you add one calorie of heat to one gram of water in an isolated container?
-When you add one calorie of heat to one gram of water in an isolated container, you expect a temperature increase of one centigrade degree.
How does the process of melting ice differ from raising the temperature of water?
-Melting ice requires adding heat without a change in temperature until the phase change is complete, whereas raising the temperature of water involves a continuous increase in temperature with added heat.
What is the amount of heat required to completely melt one gram of ice at zero degrees centigrade?
-The amount of heat required to completely melt one gram of ice at zero degrees centigrade is approximately 80 calories.
What is the term used for the energy required to change the phase of a substance?
-The term used for the energy required to change the phase of a substance is latent heat.
What are the two types of latent heat mentioned in the script?
-The two types of latent heat mentioned in the script are latent heat of fusion (change from solid to liquid) and latent heat of vaporization (change from liquid to gas).
How much heat is required to completely evaporate one gram of boiling water at 100 degrees centigrade?
-It takes 540 calories to completely evaporate one gram of boiling water at 100 degrees centigrade.
Why is the energy required to change the phase of water from solid to liquid or liquid to gas so high?
-The energy required is high because the molecules need to overcome the intermolecular forces and gain enough energy to change their state, which is significantly more than what is needed to raise the temperature by one degree centigrade.
What is the formula used to calculate the amount of heat required for a phase change?
-The formula used to calculate the amount of heat required for a phase change is Q = M * L, where Q is the heat energy, M is the mass of the substance, and L is the latent heat of the material.
How does the temperature change during the phase change process?
-During the phase change process, the temperature remains constant until the phase change is complete, even though heat is being added or removed.
What is the significance of latent heat in understanding phase changes?
-The significance of latent heat in understanding phase changes is that it quantifies the amount of energy required to change the state of a substance without changing its temperature, which is crucial in processes like melting and evaporation.
Outlines
🌡️ Phase Change and Latent Heat in Thermodynamics
This paragraph introduces the concept of phase change in thermodynamics, focusing on the transformation of materials from solid to liquid and from liquid to gas. It uses the example of one gram of water to illustrate the process. The discussion highlights the significant amount of energy, or latent heat, required for these changes. Specifically, it mentions that 80 calories are needed to melt one gram of ice at zero degrees Celsius, and 540 calories are required to evaporate one gram of boiling water at 100 degrees Celsius. The concept of latent heat is explained, distinguishing between latent heat of fusion (solid to liquid) and latent heat of vaporization (liquid to gas). The importance of understanding these energy requirements is emphasized, as they are fundamental to the study of thermodynamics.
🔥 Understanding Latent Heat of Fusion and Vaporization
In this paragraph, the focus is on the mathematical representation of the latent heat involved in phase changes. It explains that the heat required for a phase change, denoted as Q, can be calculated using the formula Q = M * L, where M is the mass of the substance undergoing the phase change and L is the latent heat. The paragraph clarifies that the latent heat of fusion is the energy needed to change a solid to a liquid, and the latent heat of vaporization is the energy needed to change a liquid to a gas. The units of latent heat are energy per gram, and the example of water is used to demonstrate that 80 calories per gram are required for fusion and 540 calories per gram for vaporization. The summary underscores the importance of recognizing the energy differences between temperature changes and phase changes in thermodynamics.
Mindmap
Keywords
💡Thermodynamics
💡Phase Change
💡Latent Heat
💡Calorie
💡Isolated System
💡Molecules and Atoms
💡Vibration
💡Melting
💡Evaporation
💡Latent Heat of Fusion
💡Latent Heat of Vaporization
Highlights
Introduction to the topic of phase change in thermodynamics and associated latent heat.
Explanation of how adding one calorie of heat to one gram of water in an isolated container would typically increase its temperature by one degree Celsius.
Discussion on the melting of one gram of ice at zero degrees Celsius and the amount of heat required for complete melting.
The concept that phase change from solid to liquid or liquid to gas requires energy, specifically latent heat.
Description of the process of atoms breaking free from each other when enough heat is added to change a solid into a liquid.
The energy required to turn water into vapor, highlighting the large amount of heat necessary compared to raising temperature.
Quantitative comparison of energy needed to raise water temperature by one degree Celsius versus melting one gram of ice.
The specific amount of heat, 80 calories, required to completely melt one gram of ice at zero degrees Celsius.
The even greater amount of heat, 540 calories, required to completely evaporate one gram of boiling water.
Explanation of latent heat and its role in phase changes without a change in temperature.
The formula Q = M * L for calculating the amount of heat required for phase change, where M is mass and L is latent heat.
Differentiation between latent heat of fusion (solid to liquid) and latent heat of vaporization (liquid to gas).
The practical example of water's phase changes and the associated latent heats of fusion and vaporization.
The units of latent heat, energy per gram or energy per mass, and their significance in calculations.
The specific latent heat values for water: 80 calories per gram for fusion and 540 calories per gram for vaporization.
The importance of understanding phase change and associated latent heat in thermodynamics for practical applications.
Transcripts
welcome to electron line and the next
topic we're going to talk about in
thermodynamics is the change of phase of
materials and the Associated latent heat
as we call it so we go back to something
we're familiar with let's say we have a
little container and of course has to be
tiny little container because we're
talking about it containing one gram of
water and one gram of water is very very
tiny but let's say we add one calorie of
heat to that container and let's say the
container doesn't change temperature
it's isolated from the water to some
insulator and we add one calorie to the
water we expect a temperature increase
to be one centigrade degree now what
would happen if you took one gram of ice
at zero degree centigrade so the ice if
you now add any heat to the ice the ice
will begin to melt and the question then
would be how much heat do we add to one
gram of ice to completely melt that one
gram of ice and secondly let's say we
have a small container that has boiling
water in it at 100 degrees centigrade
and how much heat do we have to add to
the water to completely evaporate that
water so when we go from the solid state
to a liquid state or from a liquid state
to a gas state we go to what we call a
change of phase and in order to do that
it requires energy well first of all to
go from a solid state to liquid state
you have to go from a state where the
atoms are locked in position due to the
electrical bonds and then we add enough
heat the the molecules begin to vibrate
so finally that they actually break
loose from each other and they begin to
roll over each other like marbles would
roll over each other and so then you
turn a solid into a liquid then if you
continue add more and more heat the
vibrations continue to the point where
they get so much energy that they will
actually jump free from the water and
turn into a gas or in the case of water
it turns into a vapor and again that
requires a certain amount of energy and
you'd be surprised how much energy that
takes because it only takes one calorie
to take one gram of water and increase
of a one centigrade degree but to take
one gram of ice at zero degree
centigrade and you want to completely
melt it the heat required q is equal to
80 calories technically speaking it's
actually seventy nine point seven
calories
but we typically just call it 80
calories compared to how much it takes
to raise the temperature by one degree
centigrade it takes 80 times as much to
completely melt one gram of ice at zero
degree centigrade to liquid at zero
degree centigrade in an enormous amount
of heat not only that when you take
boiling water and you want to completely
evaporate it it takes even more heat the
cure required to completely evaporate
one gram of boiling water is equal to
540 calories without the words 540 times
as much as the energy required to take
one gram of water and raise this
temperature by one centigrade degree so
there you get kind of a feel of how much
heat it requires now it turns out since
the temperature doesn't change through
the phase in other words when one gram
of ice which start at 0 degree
centigrade completely melts that water
does not melt the water will still be at
0 degree centigrade so it still will be
at the same temperature there's no
temperature change so the equation we
use for that is Q is equal to M times L
M is the mass of the substance that
we're changing to a face and L is what
we call the latent heat of the of the
material so in the case of water so the
amount of heat required is equal to the
mass 1 gram times the latent heat of
fusion as we call it so let's call this
latent heat of fusion
I said well wait a minute fusing means
you take a liquid put into a solid
that's correct but it's the same energy
required to go both ways
so if you take one gram of water and
completely freeze it to a block of ice
of one gram at 0 degree centigrade then
of course you would have to take away
from that 80 calories of heat and
likewise they have 1 gram of steam at
100 degrees centigrade and allow it to
to liquefy to condense as we call it
then of course you have to remove 540
calories of heat in order for it to go
from a gas phase to a liquid phase so
this is called latent heat of fusion so
to indicate going from a liquid to a
solid and this is called latent heat of
vaporization which means going from a
liquid state to a gas phase so the term
ecology is from a liquid to frozen or
liquid to a gas phase so it's called
latent heat of vaporization of course
water is kind of a common substance and
we commonly go from liquid to solid salt
back to liquid and all for liquid eyes
and eyes back to liquid same with the
vaporization of course latent heat of
fusion and later heat of vaporization is
something you will see in all substances
of course we can talk about that later
but any weight so this would be equal to
80 calories per gram so notice that the
units are energy per gram or energy per
mass the grams cancel out of course
you're left with calories and here for
here for this change in face you say Q
is equal to M times L in this case the L
is the latent heat of vaporization and
so that would be equal to one gram times
540 calories per gram again notice that
the grams cancel out you're left with
calories and so this would of course be
540 calories required to change one gram
of boiling water to two of gas phase and
here Q would be equal to 80 calories
that's the heat required to take one
gram of ice at zero degree centigrade
and turn it completely into a liquid so
hopefully this will give you a good
understanding of what what the phase of
change the change of phases and what two
associated heat required is which is
called the latent heat of fusion or of
vaporization
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