Specific Heat Capacity

Summary

Today's lesson focused on specific heat capacity within thermal physics for AQA A-Level. It explained how work can be done into a system's internal energy, defining specific heat capacity and measuring work done through internal energy changes. The lesson highlighted the first law of thermodynamics, detailing how heat transfer occurs from hotter to cooler substances and the role of radiation. The key formula \(\Delta Q = mc\Delta T\) was introduced, illustrating how to calculate the energy needed for a substance's temperature change. An example problem demonstrated calculating the energy required to heat water, emphasizing the importance of units and significant figures.

Takeaways

• 🔍 Specific heat capacity is a key concept in thermal physics, part of the AQA A Level Physics curriculum.
• 🔧 Work done on a system can increase or change the average kinetic or potential energy of a substance, affecting its internal energy and temperature.
• 🌡️ The first law of thermodynamics states that the change in internal energy is equal to the work done on the system.
• ↗️ An increase in kinetic energy store results in a rise in temperature, while a decrease leads to a fall.
• ♨️ Heat is transferred from hotter to cooler substances, and the rate of heat transfer is influenced by the temperature difference.
• 🌡️ The equation ΔQ = mcΔT links the work done, mass, specific heat capacity, and temperature change of a substance.
• 💧 The specific heat capacity of water is 4200 J/kg·K, which is a value often provided in exam questions.
• 🔢 The calculation of energy required to change the temperature of a substance involves the mass of the substance, its specific heat capacity, and the temperature change.
• ✅ It's crucial to use the correct units and significant figures when calculating and reporting results in physics.
• 🔙 The direction of work done is from high to low temperature, indicating an increase in internal energy when the temperature rises.

Q & A

What is specific heat capacity?

Specific heat capacity is the amount of heat energy required to raise the temperature of one kilogram of a substance by one degree Celsius (or one Kelvin) without changing its state.

How does work relate to the internal energy of a system?

Work done on a system is directly related to changing its internal energy, which can either increase or change the average kinetic or potential energy of the substance.

What is the first law of thermodynamics as mentioned in the script?

The first law of thermodynamics, as mentioned in the script, states that the change in internal energy of a system is equal to the work done on the system.

Why does heat transfer occur?

Heat transfer occurs because energy is transferred from particles with higher energy (hotter substances) to particles with lower energy (cooler substances), moving from higher temperatures to lower temperatures.

How does the potential energy store in a system relate to its internal energy?

In most objects, the potential energy store is larger than the kinetic energy store. Increasing the potential energy can increase the overall internal energy without changing the temperature.

What is the equation that links work done to a system and the resultant temperature change?

The equation that links work done to a system and the resultant temperature change is \(\Delta Q = mc\Delta T\), where \(\Delta Q\) is the energy transferred, \(m\) is the mass of the substance, \(c\) is the specific heat capacity, and \(\Delta T\) is the change in temperature.

What is the significance of the specific heat capacity of a substance?

The specific heat capacity of a substance indicates the amount of energy required to raise the temperature of one kilogram of the substance by one degree Celsius. A larger specific heat capacity means more work is needed for a temperature increase.

How does the specific heat capacity affect the internal energy of a substance?

A substance with a higher specific heat capacity will store more kinetic energy per temperature change, resulting in more internal energy and particles moving on average at a higher speed.

What is the direction of heat transfer in terms of temperature?

Heat is always transferred from hotter substances to cooler substances, meaning it moves from areas of higher temperature to areas of lower temperature.

Can you provide an example calculation using the specific heat capacity equation from the script?

Yes, to calculate the energy required to raise the temperature of 5 kilograms of water from 20°C to 100°C, using the specific heat capacity of water (4200 J/kg·K), the calculation is \(\Delta Q = 5 \text{ kg} \times 4200 \text{ J/kg·K} \times (100 - 20) \text{ K} = 1.7 \times 10^6 \text{ J}\).

Outlines

00:00

🔥 Introduction to Specific Heat Capacity

This paragraph introduces the concept of specific heat capacity within the realm of thermal physics, specifically for AQA A Level Physics. It discusses the calculation of specific heat capacity, the impact of work done on a system's internal energy, and the distinction between changes in kinetic and potential energy. The first law of thermodynamics is mentioned, highlighting the relationship between work done and changes in internal energy. The focus is on how work affects the kinetic energy store, leading to temperature changes. The direction of heat transfer is also explained, emphasizing the transfer from hotter to cooler substances and the role of temperature difference in heat transfer speed. The concept of internal energy change through work is reiterated, with an equation linking work done to temperature change (ΔQ = mcΔT).

05:01

💧 Understanding Specific Heat Capacity

This paragraph delves deeper into the concept of specific heat capacity, defining it as the energy required to raise the temperature of one kilogram of a substance by one degree Kelvin without changing its state. It explains the relationship between specific heat capacity, the kinetic energy store, and temperature change. The paragraph uses an example to illustrate how to calculate the energy needed to raise the temperature of water from 20°C to 100°C, using the specific heat capacity equation (ΔQ = mcΔT). The importance of units and significant figures in calculations is emphasized, and the direction of work done is related to temperature changes. The summary concludes with a recap of the lesson's objectives, reinforcing the understanding of how work is done into a system's internal energy and how to measure it using specific heat capacity.

Keywords

💡Specific Heat Capacity

Specific heat capacity is a property of a material that quantifies the amount of heat required to raise the temperature of one unit mass of the substance by one degree Celsius (or one Kelvin). In the context of the video, it is a key concept used to explain how much energy is needed to change the temperature of a substance. The video states that 'the specific heat capacity is the energy needed to raise one kilogram of a substance by one degree Kelvin without changing state,' illustrating its importance in thermal physics.

💡Thermal Physics

Thermal physics is a branch of physics that deals with the effects of heat and temperature on matter. The video focuses on this area, particularly on the specific heat capacity, which is a fundamental concept in understanding how substances respond to changes in temperature. The script mentions that the lesson is part of the 'thermal physics topic in AQA A Level Physics,' indicating its relevance to the broader study of heat and its effects.

💡Internal Energy

Internal energy refers to the total energy contained within a system, which includes both the kinetic and potential energy of its particles. The video explains that work done on a system can increase its internal energy, either by raising the average kinetic energy (and thus the temperature) or by increasing the average potential energy (and thus changing the state). The script uses the concept to discuss how 'changing the internal energy of the system is doing work' and how this relates to the first law of thermodynamics.

💡First Law of Thermodynamics

The first law of thermodynamics, also known as the law of conservation of energy, states that energy cannot be created or destroyed, only converted from one form to another. In the video, this law is used to explain that the change in internal energy of a system is equal to the work done on the system, as stated in the script: 'the change in internal energy is equal to the work done to the system.' This principle is fundamental to understanding energy transfer in thermal processes.

💡Kinetic Energy

Kinetic energy is the energy that a substance possesses due to the motion of its particles. In the video, it is mentioned that increasing the kinetic energy store of a substance results in an increase in temperature. The script explains that 'an increase in the kinetic energy store of the internal energy would result in an increase in the temperature of the system,' highlighting the direct relationship between kinetic energy and temperature.

💡Potential Energy

Potential energy is the stored energy of a substance due to the position or condition of its particles. The video script contrasts kinetic and potential energy, noting that 'for most objects, the potential energy store is larger than the kinetic energy store.' It also explains that increasing the potential energy can lead to a change in the state of the substance, such as melting or boiling.

💡Heat Transfer

Heat transfer is the movement of thermal energy from one body or substance to another. The video discusses how heat is transferred from hotter to cooler substances, as mentioned in the script: 'heat is always transferred from hotter substances to cooler substances.' It also touches on the mechanisms of heat transfer, including conduction and radiation.

💡Temperature Change

A temperature change refers to the increase or decrease in the degree of hotness or coldness of a substance. The video uses this concept to explain how work done on a system can result in a temperature change, as indicated by the equation 'delta q is equal to mc delta t,' where 'delta t' represents the change in temperature. The script provides an example of calculating the energy needed to raise the temperature of water, demonstrating the practical application of this concept.

💡Joules

Joules are the unit of measurement for energy in the International System of Units (SI). The video script mentions that 'delta q is energy transferred or work done so is measured in joules,' emphasizing the use of joules to quantify the heat energy transferred into or out of a system. This unit is crucial for performing calculations related to specific heat capacity and energy changes.

💡Significant Figures

Significant figures are the digits in a number that carry meaning contributing to its precision. The video script advises to 'always remember to give your answers with the correct units and to the correct number of significant figures,' highlighting the importance of precision in scientific calculations. This concept is crucial for ensuring that the results of experiments and calculations are accurately reported.

Highlights

Introduction to specific heat capacity as part of thermal physics in AQA A Level Physics.

Explaining how to calculate the specific heat capacity of a substance.

Defining specific heat capacity and its role in measuring work done into a system's energy.

Discussing the impact of work on internal energy and its two forms: kinetic and potential energy.

The first law of thermodynamics and its relation to changes in internal energy.

Heat transfer direction from hotter to cooler substances and its relation to particle energy.

Heat transfer mechanisms: conduction and radiation.

The effect of heating a substance on particle kinetic energy and temperature.

Equation linking work done to a system and temperature change: Δq = mcΔT.

Importance of units and significant figures in thermodynamics calculations.

Definition of specific heat capacity as energy needed per kilogram for a 1 K temperature change.

Implications of a substance's high specific heat capacity on internal energy storage.

Practical calculation example using the specific heat capacity equation.

Explanation of the calculation process for heating 5 kg of water from 20°C to 100°C.

Emphasis on the correct units and the significance of the temperature change in calculations.

Summary of the lesson's key learnings on specific heat capacity and its applications.

Closing remarks and a thank you note for watching the lesson on specific heat capacity.

Transcripts

hello and welcome to today's lesson on

specific heat capacity

which is part of the thermal physics

topic in aqa a level physics

so in today's lesson we're going to look

at how you can calculate the specific

heat capacity of a substance

so if we've been successful and learned

in today's lesson

we can explain how work can be done into

the internal energy of a system

we can define specific heat capacity of

a material

and we can measure the work done into

the energy of a system

using the internal energy of that system

so we're going to look at the following

part of the aqa a-level physics

specification

3.6.2.1 thermal energy transfer

now when work is done to the internal

energy of a system

that energy can be used to either

increase or

change the average kinetic energy of the

substance or it can be used to increase

the average potential energy

of the substance either one will change

the internal energy

now if you change the kinetic energy of

the internal energy

you'll be changing the temperature of

the substance if you change the

the potential energy stall of the

internal energy you'll be changing the

state

of the substance now you'll notice in

the diagram here we have a

representation

of the internal energy of a system now

for most

objects the potential energy store is

larger than the kinetic energy store

so as we said before if we increase the

potential energy we can

increase the overall internal energy now

remember

changing the internal energy of the

system is doing work

you must do work to change that internal

energy store of a substance

whilst also if we ch increase or change

the kinetic energy store of the

substance we will also be changing or

increasing

the internal energy we'll be doing work

again

now remember the change in internal

energy is equal to the work

done to the system this is the first law

of thermodynamics

now in this lesson we're only going to

be focusing on

how we increase or change the kinetic

energy store of the

internal energy of the system now an

increase in the kinetic energy store

of the internal energy would result in

an increase in the temperature of the

system

whilst a decrease in kinetic energy

store would result in a decrease in

temperature of the system

now it's important to note that heat is

always transferred from hotter

substances

to cooler substances so heat energy is

transferred

from higher temperatures to lower

temperatures so the direction of work

done is from an area of high temperature

to an area of low temperature now this

occurs because the particles with more

energy transfers some energy to the

particles with

less energy now the higher the

difference in temperature between the

two substances

the faster the heat transfer between the

substances

now as well as this idea of particles

with more energy transferring some

energy to particles with

less energy heat is also transferred by

radiation

so hotter substances will radiate heat

quicker

than cooler substances transferring that

heat energy to

the cooler cooler surroundings now

when you heat a substance the particles

in the substance

gain kinetic energy so when we say heat

is transferred into a substance

we say work is done into the system

because the

overall internal energy is increasing

now if we are placing heat energy into

the substance

the kinetic energy of the particles

increases

so therefore the temperature of the

substance itself

increases now doing work into or

out of a substance will cause a

temperature change in the

substance now the equation that links

work done

in an internal system and the resultant

temperature change of the substance

is it is the following delta q is equal

to mc

delta t where delta q is the energy

transferred the heat

transferred the work done m is the mass

of the substance

c is specific heat capacity and delta t

is the change in temperature of the

substance

now carrying out work into the system

placing heat into or out of the system

causes a change in the kinetic energy

stall and thus the temperature

now it's important to note that delta q

is energy transferred or work done so is

measured in joules

the mass is measured in kilograms and

the change in temperature

is measured in kelvins now it's

important to note that as this is a

delta t

it's a temperature change you can use

either celsius or kelvins

to actually work out this value because

the change in kelvin on the change in

celsius is the same value

now the last thing we need to look at is

specific heat capacity

now we can define heat capacity as the

energy supplied to a substance to change

the particle movement

to make the temperature change by one

kelvin

now that is heat capacity now specific

means per kilogram

so the specific heat capacity is the

energy needed

to raise one kilogram of a substance by

one degrees

kelvin without changing state so just to

clarify

the specific heat capacity is the link

between the kinetic energy store change

of the internal energy of the substance

and the resultant change in temperature

of the substance

now the larger the specific capacity

heat capacity of the substance

the more work is needed to be done to

raise the temperature by 1 degrees

celsius or kelvin now the larger the

specific heat capacity of a substance

the more kinetic energy is stored as

internal energy per

increase in temperature so what this

means

is that an object with a high specific

heat capacity

will store more kinetic energy per

temperature change

so we'll have more internal energy so if

you have

two materials which undergo the same

temperature change

the object which has the higher specific

heat capacity

will store more internal energy so

this means that the object with the

highest heat capacity

will have more internal energy so we'll

have a larger kinetic energy store and

have particles moving on average at a

higher speed

so let's now look at an example of a

calculation with the specific heat

capacity equation

so calculate the energy that must be

supplied to raise the temperature

of 5 kilograms of water from 20 degrees

to 100 degrees celsius

so the specific heat capacity of water

is 4200 joules per kilogram kelvin

now you will be given that in a question

in your examination

now the equation is delta q is equal to

mc

delta t now you'll have noticed in this

example i wrote delta t the change in

temperature as

t2 minus t1 the final temperature minus

the starting temperature

we then put our values in so 5.0 times

by 4200 times by

100 minus 20 which is 80. so we get our

answer

to be delta q the work done into the

system

is 1.7 times 10 to the 6 joules now

remember as the temperature change is

the same in degrees celsius as it is in

kelvin

that means if you were given temperature

in degrees celsius then you can

calculate the temperature difference

in that particular unit now you've

always got to remember as well

to give your answers with the correct

units and to the correct number of

significant figures

and finally always check to see if your

answer looks sensible

now again remember the direction in

which work is done

into the particular system now because

the temperature

is going higher it's going from 20 to

100 degrees

the work would be doing into the system

because the internal energy is getting

higher

so we can say that's 1.7 times 10 to the

6 joules is being placed

into the substance to cause this

temperature increase

obviously it will be the other way

around if it was a temperature decrease

so let's summarize what we've learned in

today's lesson

for a change in temperature q is equal

to m c delta theta

where c is specific heat capacity and in

this case delta theta

is the change in temperature so if we've

been successful and learned in today's

lesson

we should be able to explain how work

can be done into the

internal energy of a system we can

define specific heat capacity of

material

and finally measure the work done into

the energy of a system

using the internal energy of the system

so thank you very much for watching

today's lesson

on pacific heat capacity which is part

of the thermal physics topic

in aqa a level physics thank you very

much for watching and have

a lovely day