Specific Heat Capacity + Latent Heat - GCSE & A-level Physics (full version)

Summary

This 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

00:00

🔥 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.

05:01

🔧 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.

10:02

🧊 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.

Keywords

💡Heat

Heat is defined as a type of energy and is measured in joules. In the context of the video, it's important to distinguish heat from temperature, as heat is the energy transferred between objects due to a difference in temperature. The script emphasizes that while adding heat to an object increases its temperature, they are not synonymous.

💡Temperature

Temperature is described as the 'hotness' of an object and is measured in degrees Celsius or Kelvin. The script clarifies that temperature is a measure of how fast particles are vibrating within an object. It is a central concept in the video, used to explain the relationship between heat and the energy required to change an object's temperature.

💡Joules

Joules are the units used to measure heat, as well as other forms of energy. The script uses joules to quantify the amount of heat energy involved in processes such as heating an object or causing a phase change.

💡Kelvin

Kelvin is a unit of temperature measurement that is superior to Celsius, as mentioned in the script, because it can be used for a broader range of scientific applications. However, for simplicity, the script primarily uses degrees Celsius.

💡Specific Heat Capacity

Specific heat capacity is the amount of energy required to raise the temperature of one kilogram of a substance by one degree Celsius or Kelvin. The script explains that it is a property specific to each material and is measured in joules per kilogram per degree Celsius (J/kg°C). It is used to calculate the energy needed to change the temperature of a substance.

💡Mass

Mass is the measure of the amount of matter in an object, typically measured in kilograms. The script mentions mass in the context of the formula for calculating the energy required to change an object's temperature, emphasizing that the larger the mass, the more energy is needed for a given temperature change.

💡Energy

Energy is a central theme in the video, referring to the capacity to do work or cause change. The script discusses energy in the context of heat transfer, specific heat capacity, and phase changes, using the formula Energy = mass × specific heat capacity × change in temperature.

💡Latent Heat

Latent heat is the energy required to change the phase of a substance without changing its temperature. The script differentiates between the latent heat of fusion (melting) and the latent heat of vaporization (boiling), explaining that these are different from specific heat capacity and are measured in joules per kilogram.

💡Phase Change

A phase change is the process by which a substance transitions from one state of matter to another, such as from solid to liquid or liquid to gas. The script uses phase changes to illustrate the concept of latent heat, explaining that energy is absorbed or released during these processes without a change in temperature.

💡Experiment

The script describes an experiment to determine the specific heat capacity of a material, such as iron, by measuring the energy supplied by a heater and the resulting change in temperature. This practical application demonstrates how theoretical concepts are applied in a real-world context.

💡Uncertainty

Uncertainty is mentioned in the context of experimental measurements, where some energy may be lost to the surroundings. The script suggests that understanding and addressing sources of uncertainty, such as through insulation, is important for improving the accuracy of experiments.

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