Laws of Thermodynamics

THERMODYNAMICSAN INTRODUCTION

WHAT IS THERMODYNAMICS?

The study of relationships involving heat, mechanical work, and other aspects of energy and energy transfer

LAWS OF THERMODYNAMICS

First LawSecond LawZeroth LawThird Law

FIRST LAW OF THERMODYNAMICS


How does a hot cup of coffee get cold?

How does ice melt?How is the 1st law exhibited by a car

engine?


Law of Conservation of Energy“Energy cannot be created nor

destroyed”

Visualize a hot cup of coffee that is placed on top of a

table.

After a few minutes, the coffee gets cold.

Is energy destroyed?

Energy was not destroyed.

Energy was transferred to the environment.

HEAT

HEAT

HEAT

HOT COOL

HEAT

HEAT

HEAT

COFFEE ENVIRONMENT

CONSERVATION OF ENERGY

Another example is a chain of energy transfer that starts with the microwave oven.


1ELECTRICAL energy is converted

to THERMAL energy


2 HEAT is TRANSFERRED to the

food we are cooking


3 After cooking, we take out the

food out of the oven and expose it to the environment and, thus, HEAT from the food is transferred to the environment


4 We get hungry. We eat the food

and the CHEMICAL energy in the food is converted to KINETIC energy as we

do our daily activities.


5 The energy transfer goes on…

…Continue the chain


How does a hot cup of coffee get cold?

How does ice melt?How is the 1st law exhibited by a car

engine?

SECOND LAW OF THERMODYNAMICS


Why can’t there be a 100% efficient engine?

When are you more efficient, when you focus on one thing or when you multitask?


There is a limit to the availability of energy and the ways in which it can be used or converted

No such thing as a 100% efficient engine

Follows the concept of entropy

(Entropy = energy degradation)


Imagine that you have a pot with a plant in it. As you were watering it, you noticed grass

growing around the plant.

How sure are you that the water you are giving is

absorbed by the plant alone?

FOLLOWS THE CONCEPT OF ENTROPY

Entropy is simply the degradation of energy.

Due to the continuous process of energy transfer and conversion, energy is

degraded.

FOLLOWS THE CONCEPT OF ENTROPY

Let’s play the game “Pass the Message”

WHY CAN’T THERE BE A 100% EFFICIENT ENGINE?

Friction

Heat

Heat is released by the engine etc


Why can’t there be a 100% efficient engine?

When are you more efficient, when you focus on one thing or when you multitask?

ZEROTH LAW OF THERMODYNAMICS


Thermal Equilibrium


We leave two cups of coffee (where one is observably hotter than the other) on the

kitchen table and we just leave them there.

After 30 minutes what will we notice about the two cups of coffee?

They will both cool down and will seemingly both have the same

temperature.

ENVIRONMENTHEAT HEAT

ENVIRONMENT


ENVIRONMENT

AB

C

THIRD LAW OF THERMODYNAMICS


Possibility of Absolute Zero temperature


Is it possible?


It is impossible to reduce any system to absolute zero in a finite series of operations

- In order to have an object at Absolute Zero

temperature, an abundant amount of matter at

Absolute Zero temperature must pre-

exist

SUMMARY

4 laws of Thermodynamics- Law of Conservation of Energy- Entropy- Equilibrium- Absolute Zero

HOMEWORK(I WHOLE INTERMEDIATE PAPER)

1. We can notice the tubing system at the back of the refrigerator. Where does the heat of the tubing come from?

2. Why is an air conditioner placed in a window and not on the floor?

3. Could we cool the house if we leave the refrigerator door open?

Laws of Thermodynamics

Science

Transcript of Laws of Thermodynamics