Specific Heat Capacity + Latent Heat - GCSE & A-level Physics (full version)
Summary
TLDRThis educational script explains the distinction between heat and temperature, emphasizing that heat is a form of energy measured in joules, while temperature is the 'hotness' of an object, measured in degrees Celsius or Kelvin. It introduces the concept of specific heat capacity, crucial for understanding how different materials respond to heat, with water's specific heat capacity given as 4,200 joules per kilogram per degree Celsius. The script also touches on specific latent heat, the energy required to change a substance's state, and discusses experimental methods to determine specific heat capacity. It concludes with a look at combined processes involving both heat transfer and phase changes, highlighting the importance of practice in mastering these thermodynamic concepts.
Takeaways
- 🔥 Heat is a form of energy measured in joules, distinct from temperature, which is measured in degrees Celsius or Kelvin.
- 🌡️ The Kelvin scale is preferred for scientific measurements because it can represent absolute zero and allows for more precise calculations.
- 📐 The relationship between heat and temperature is given by the formula: Energy (Q) = mass (m) × specific heat capacity (c) × change in temperature (ΔT).
- 🌡️ Specific heat capacity (c) is a material-specific property that quantifies the energy needed to raise the temperature of one kilogram of a substance by one degree Celsius or Kelvin.
- 💧 For water, the specific heat capacity is 4,200 joules per kilogram per degree Celsius, indicating it requires more energy to change its temperature compared to other substances.
- ⚖️ To determine the specific heat capacity of a material, one can measure the mass of the substance, the energy supplied, and the resulting change in temperature, then rearrange the formula to solve for c.
- 🔋 The energy supplied to a substance can be calculated by measuring the voltage, current, and time for which the substance is heated.
- ❄️ Specific latent heat refers to the energy required to change the state of a substance from solid to liquid (fusion) or liquid to gas (vaporization) without changing its temperature.
- 🔥 The process of melting or vaporizing involves energy used to break bonds, resulting in a constant temperature phase during these state changes.
- 🧊 When calculating the total energy needed for a substance to change state and temperature, the specific heat capacity for temperature change and the latent heat for phase change must be considered together.
- 🔄 In scenarios involving energy transfer between two substances, such as a hot liquid and ice, the energy equation must account for both the change in temperature and the phase change of the substances involved.
Q & A
What is the difference between heat and temperature?
-Heat is a form of energy measured in joules, while temperature is a measure of how hot an object is, typically measured in degrees Celsius or Kelvin. Although related, they are not the same; heat is the energy transferred due to temperature difference, whereas temperature is a measure of the average kinetic energy of the particles in a substance.
Why is the Kelvin scale considered superior to the Celsius scale for measuring temperature?
-The Kelvin scale is considered superior because it is an absolute temperature scale, starting at absolute zero, the theoretical lowest temperature where all molecular motion stops. It allows for more scientific and precise calculations, especially in fields like physics and engineering.
What is the formula to calculate the change in energy when heat is transferred to or from an object?
-The formula to calculate the change in energy (ΔE) is ΔE = mcΔT, where m is the mass of the object, c is the specific heat capacity of the material, and ΔT is the change in temperature.
What is specific heat capacity and how is it measured?
-Specific heat capacity (c) is the amount of energy required to raise the temperature of one kilogram of a substance by one degree Celsius (or Kelvin). It is measured in joules per kilogram per degree Celsius (J/kg°C) or joules per kilogram per Kelvin (J/kg·K).
How does the specific heat capacity of water compare to other materials?
-Water has a high specific heat capacity of 4,200 J/kg°C, which means it takes a significant amount of energy to change its temperature. This is why water is often used as a coolant or for temperature regulation, as it can absorb or release a lot of heat with little change in its own temperature.
Can the specific heat capacity be given in joules per gram per degree Celsius, and what would it mean for water?
-Yes, specific heat capacity can be given in joules per gram per degree Celsius. For water, if the specific heat capacity is given in joules per gram, it would be 4.2 J/g°C, indicating that it takes 4.2 joules to raise the temperature of one gram of water by one degree Celsius.
How can you experimentally determine the specific heat capacity of a material like iron?
-You can determine the specific heat capacity of iron experimentally by measuring the mass of an iron block, applying a known amount of heat to it using a heater, and observing the change in temperature. The specific heat capacity can then be calculated using the formula c = ΔE / (mΔT), where ΔE is the energy supplied, m is the mass, and ΔT is the change in temperature.
What is the difference between specific heat capacity and specific latent heat?
-Specific heat capacity is the energy required to raise the temperature of a substance without changing its state, while specific latent heat is the energy required to change the state of a substance (e.g., from solid to liquid or liquid to gas) at a constant temperature.
How does the energy input affect the temperature during the melting or vaporization of a substance?
-During melting or vaporization, the energy input is used to break the bonds between particles to change the state of the substance rather than to raise its temperature. This results in a constant temperature during the phase change until all the substance has changed state.
What is the significance of the term 'specific latent heat' in the context of phase changes?
-The term 'specific latent heat' refers to the amount of energy absorbed or released by a unit mass of a substance during a phase change at constant temperature. It is significant because it quantifies the energy involved in the process of melting (latent heat of fusion) or vaporization (latent heat of vaporization).
How can you calculate the total energy required to change a substance from one state to another, such as from ice to water vapor?
-To calculate the total energy required, you need to consider both the energy needed to raise the temperature (using specific heat capacity) and the energy needed for phase changes (using specific latent heat). The formula would be Total Energy = (mass × specific heat capacity × change in temperature) + (mass × latent heat of fusion) + (mass × latent heat of vaporization).
What is the concept of energy transfer between two substances with different specific heat capacities, and how can it be calculated?
-The concept of energy transfer between two substances involves the exchange of thermal energy, leading to a change in temperature for both substances. It can be calculated using the principle of conservation of energy, where the energy lost by one substance (due to a decrease in temperature) is equal to the energy gained by the other (due to an increase in temperature). The calculation involves setting up an equation based on the specific heat capacities, masses, and temperature changes of both substances and solving for the unknown temperature.
Outlines
🔥 Understanding Heat and Temperature
This paragraph introduces the fundamental concepts of heat and temperature, emphasizing their differences. Heat, a form of energy measured in joules, is distinguished from temperature, which is about the 'hotness' of an object and measured in degrees Celsius or Kelvin. The script explains that temperature reflects the speed of particle vibration within a substance. It also introduces the concept of specific heat capacity (SHC), which is the energy required to raise the temperature of a substance by one degree Celsius or Kelvin, and is measured in joules per kilogram per degree Celsius. The specific heat capacity of water is given as 4,200 joules per kilogram per degree Celsius. The paragraph concludes with a brief introduction to the experimental determination of SHC.
🔧 Calculating Specific Heat Capacity and Latent Heat
The second paragraph delves into the process of calculating specific heat capacity and latent heat. It explains how to determine the specific heat capacity of a material, such as iron, through an experiment involving a heater, ammeter, voltmeter, and a block of the material. The energy supplied to the material is calculated using the formula for power (voltage times current) multiplied by time, taking into account potential energy losses to the surroundings. The specific heat capacity is then found by dividing the supplied energy by the product of the material's mass and the change in temperature. The paragraph also introduces the concept of specific latent heat, which is the energy required to change the state of a substance from solid to liquid or liquid to gas, and how it differs from specific heat capacity.
🧊 Energy Transfers and Phase Changes
The final paragraph discusses the complexities of energy transfers and phase changes, particularly when dealing with substances undergoing both temperature change and state change simultaneously. It presents a scenario involving ice and orange juice, which have different specific heat capacities, and explains how to calculate the energy exchanges when they reach a common temperature. The paragraph introduces the formulas for calculating the energy needed to raise the temperature (S AC) and to melt a substance (SL H), and how to combine these to find the total energy required for a substance to change state and temperature. It also touches on the importance of practice in understanding these concepts and solving related problems.
Mindmap
Keywords
💡Heat
💡Temperature
💡Joules
💡Kelvin
💡Specific Heat Capacity
💡Mass
💡Energy
💡Latent Heat
💡Phase Change
💡Experiment
💡Uncertainty
Highlights
Heat is not the same as temperature; heat is a form of energy measured in joules, while temperature is measured in degrees Celsius or Kelvin.
The Kelvin scale is superior for scientific purposes due to its ability to represent absolute zero.
Temperature is a measure of how fast particles are vibrating within an object.
Heat input increases an object's temperature, but the two are distinct concepts.
The relationship between energy, mass, and temperature change is given by the formula Energy = mass × specific heat capacity × change in temperature.
Specific heat capacity (c or shc) is the energy required to raise the temperature of one kilogram of a substance by one degree Celsius or Kelvin.
Water has a specific heat capacity of 4,200 joules per kilogram per degree Celsius.
The specific heat capacity can vary between substances, affecting how they respond to the same amount of heat.
To calculate the specific heat capacity of a material, one can use the rearranged formula ΔQ = mcΔΘ.
An experiment can determine specific heat capacity by measuring the energy supplied to a substance and its resulting temperature change.
Energy supplied to a substance may not entirely go into temperature change due to energy loss to the surroundings.
Sources of uncertainty in experiments can be addressed by improvements such as insulation.
The specific latent heat is the energy required to change the state of a substance without changing its temperature.
The latent heat of fusion and vaporization are different for each substance and state change.
When a substance melts or vaporizes, the temperature remains constant as energy is used to break bonds rather than increase temperature.
The energy needed to change a substance from solid to liquid and then to gas can be calculated using specific heat capacities and latent heats.
In problems involving energy transfer between substances with different specific heat capacities, equations can be set up and solved for the final common temperature.
Practical application of these concepts requires understanding and practice to solve complex problems involving multiple substances and state changes.
Transcripts
now it's really important that you
understand that heat is not the same as
temperature heat is a type of energy and
as such is measured in joules
temperature
well the GCSE definition is a bit
wishy-washy is the hotness of an object
and if measured in degrees Celsius at
GCSE a day level we measure it in Kelvin
now these units are very very similar
but the Kelvin is far superior because
we can do more with it but for now we're
just going to stick with degrees Celsius
if you really want to know what it
actually is if actually how fast
particles are vibrating in an object now
don't get me wrong the more heat you put
into something the higher the
temperature gets but they are not the
same thing is there a way to tell how
much the temperature of something goes
up by if we put so much heat in yes
there is we can say that energy is
equals to mass because of course the
bigger something is the more that energy
is going to spread out times the change
in temperature as measured in degrees C
kilograms see it for mass now I'm going
to put a delta in front of here Delta if
you haven't seen this before means
change in energy change in anything so
we have a change in energy with putting
energy in or taking the energy out and
we're causing a change in temperature so
we're missing something here something
that's going to be specific for a
certain material you might or might not
know that if you give one kilogram of
iron a thousand joules and you give one
kilogram of water a thousand joules
they're actually not going to end up at
the same temperature what do we call
this thing that we're missing here we
call it specific heat capacity and the
unit of this how if we rearrange it we
get joules per kilogram
degree C or joules per kilogram per
Kelvin or we can call this Sh C for
short sh t the textbook definition is
the energy required to raise the
temperature of one kilogram of a
substance by one degrees Celsius or 1
degree Kelvin is the same thing in this
case now for water sh c is 4,200 joules
per kilogram per degree C in other words
if you have a kilogram of water and you
want to raise the temperature from say
20 21 degrees C so you're raising the
temperature by 1 degree C you need 4,200
joules of energy now it is possible for
you to be given an SH C in terms of
joules per gram per degree C so just be
careful if you're given an SH C in
joules per gram instead and you need to
measure mass in grams not kilograms but
that should be fairly obvious with the
question that you're given if that's the
case the SHC would actually be just 4.2
joules per gram per degree C for water
in that case so how can you calculate
the SHC for a material then well let's
have a look at our equation again an
alternative version of this equation if
you're doing a level is actually Delta Q
because Q is heat a level going to be MC
so symbol let me give two s HC Delta
Theta theta again usually as an angle
but in this case it means temperature
energy mass fh sea change in temperature
so let's say that we wanted to find out
the specific capacity for a material now
we could use this for any material
really there would be a liquid or a
solid boat let's try to find out the
specific capacity of iron so what we do
is we get an iron block like that and
what we do is weigh it on a balance and
find out the mass and we also have a
thermometer that's put in there as well
and we can have a little bit of water in
the hole as well
to make sure that it's the right
temperature what we then have is a
heater that we put inside of this block
and this heater is attached to a battery
or power pack and we're going to have an
ammeter as well and obviously we're
going to have a voltmeter as well so we
can measure the voltage across this
heater now we know that power supplied
by a battery is equals to voltage times
current or P equals V I to turn it into
energy energy supplied all we need to do
is times this by the number of seconds
that it's on for so it's just going to
be V I times T voltage across the heater
times the current times the time so long
as you've got a constant voltage or
potential difference and current then
you can find out how much energy is
supplied to the block by the heater now
we've got to be careful here because we
know that some of the energy is going to
be lost to the surroundings so you have
to take this value with a pinch of salt
but it's a good opportunity to talk
about sources of uncertainty and how you
might improve the experiment in the
future like insulation that kind of
thing so once you have this amount of
energy that's been supplied to the block
we know that that has to be the same as
the energy needed to raise the
temperature of the block if you know the
mass and you know the change in the
temperature all you have to do then is a
rearranged for the specific heat
capacity so the specific heat capacity
of something C or s HC
no matter how you write it it's going to
be equals so the change in energy
divided by the mass times change in
temperature so let's say that all
together we find by times in the voltage
times the current and time that we end
up with an energy of 8880 joules that's
the number of joules of energy supplied
to the iron block now this iron block is
two kilograms it's got two kilograms of
mass and the change in temperature
it went from 20 degrees to 30 degrees so
putting this in the find out specific
heat capacity we know that we put eight
thousands 880 joules then we divide that
by the mass which is two times the
change in temperature which is just
going to be ten and that ends up being
four hundred and forty-four joules per
kilogram per degree Celsius so there's
another thing that's fairly similar
called specific latent heat now I'm
going to put specific in brackets
because sometimes you'll just see it
called the latent heat and instead of
this being the energy to raise the
temperature of something it's actually
the energy required to melt or vaporize
one kilogram of substance in order to
melt one kilogram of ice from solid to
liquid we need energy and then if we've
got a liquid water to vaporize it
turning into a gas we need energy there
as well
whereas we say that the specific heat
capacity of a substance is the same no
matter what state it's in solid liquid
or gas the energy needed to melt a
substance from solid to liquid is
actually going to be different from the
energy needed to vaporize it so we do
have latent heat of fusion so that's
going to be melting and also we have
latent heat of vaporization so the
energy required to melt something or
they provide something that energy is
going to be equals to the mass in
kilograms times the latent heat el in
order to find out the latent heat all
you have to do is find out the energy
needed to melt something then divide it
by the mass of the substance that you
are melting the units of this joules per
kilogram or I can write it like this now
then let's say I put some ice inside of
a kettle and I heat it up over time the
temperature of the ice is going to rise
something weird happens when it hits
zero degrees of course it's going to
melt but for a period of time the
temperature actually stays constant
that's why it melts once all of the ice
is melted it carries on heating up then
once it hits 100 degrees C the same
thing happens again the temperature
stays constant while it vaporizes turns
into a gas if I
some way of heating it up even further
then I could raise the temperature of
the water vapor as well so here we have
ice here we have liquid water and here
we have vapor water vapor I really want
to call it steam because while steam has
little droplets of liquid water in as
well so we're just gonna call it water
vapor now why is the temperature staying
constant well it melts and why is being
vaporized here the energy that we put in
from the kettle is being used to raise
the temperature here before it can
increase the temperature even further
the energy first has to break bonds in
order to melt it or vaporize it here so
while melting or evaporating the energy
is used to break bonds not raise the
temperature so that gives a constant
temperature while all of the bonds are
broken if we were cooling something down
say we were cooling water vapor del then
we'd see the same thing again if we went
backwards the temperature would decrease
and then once I hit a hundred degrees
we'd have a flat line what's happening
well one is cooling down energy is being
given out well while it's condensing
here what's happening bonds are actually
being remade if bonds are being remade
then actually energy is given out from
those bonds so in up with a constant
temperature once all the bonds have
remade and it can carry on cooling down
and so on and so forth so that's pretty
much where the GCSE ends but with a
level you need to figure out how much
energy is needed not only to raise the
temperature for something or melt it or
vaporize it but actually both at the
same time let's say that we have ice at
a certain temperature and we want to
find out how much energy it takes to get
to here it's got to go from ice all the
way to liquid water here but in order to
do that it has to go through the process
of being melted as well so this energy
is needed to raise the temperature and
melt which formula do we use for raising
temperature we use s AC and melting we
use SL H now we could figure out what
temperature it is from here to zero
degrees if it's water and then find out
how much energy it is to melt it and
then find out how much n
is to raise the temperature up to here
but what we can do is go straight from
here to here without change in
temperature so there's going to be M C
delta T I'm going to call it delta T
naught Delta Theta it's about change in
temperature is from here to here and
then we need to add on the energy needed
to melt it as well so that's just going
to be M L and you can factorize this for
the mass as well the difficulty comes
when you have questions where you have
two objects that are transferring energy
between each other and both of their
temperatures are changing so let's say
we have a drink I'm going to say it's
orange juice so it has a different
specific heat capacity to water and
we've got some ice in there as well
and I can say that my ice when I put it
in here was minus five degrees C we know
that energy is going to be given from
the honest juice to the ice in order to
melt it and also raise its temperature
so we're going to end up ultimately at a
common temperature so how do we
represent this and figure this out what
we can say is that for the orange juice
the energy that's given out when it's
temperature is decreased it's going to
be M mass of the orange juice times the
specific heat capacity of the orange
juice times the temperature change but
we know whatever that temperature change
is going to be it's going to be 20 minus
whatever the new temperature is so let's
call that T what about the ice we know
that we have a certain mass of ice and
that's got a certain specific capacity
as well and we know that we're going to
have a change in temperature as well but
whatever this change in temperature is
we know that it's going to end up at the
same temperature as your excuse
ultimately so we can put T in there as
well now we can take away minus five so
we have the energy given out by the
orange juice is going to be given to the
ice but assuming that the ice turns into
a liquid as well which it probably will
we know that the energy is not only
going to be due to specific heat
capacity the raising of the temperature
but it's also going to be equals to the
energy needed to melt it so we've just
created an equation which we can then
solve for the new common temperature all
you have to do is rearrange get all the
T's on one side
and then solve for t obviously if you
had two substances that didn't change
state then you wouldn't need that
specific latent heat energy and there we
can just deal with our specific heat
capacity energies instead so it seems
quite simple but definitely one of those
cases where practice practice practice
is the key so that specific heat
capacity and specific lighting heats I
hope that helps if it did please leave a
like and if you have any questions or
comments and please leave them down
below and I'll see you next time
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