for Teachers for Schools for Working Scholars
for Teachers for Schools for Working Scholars
Copyright
Course Navigator
Heat Transfer & Phase ChangesNext Lesson 

Mechanical Equivalent of Heat

Chapter 3 /  Lesson 8   Transcript
Try it risk-free for 30 days

An error occurred trying to load this video.

Try refreshing the page, or contact customer support.

Coming up next: Heat Transfer & Phase Changes

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
 Replay
Your next lesson will play in 10 seconds
  • 0:01 What is Heat?
  • 1:33 Early Historical Views of Heat
  • 2:59 Link Between Work & Heat
  • 5:16 Lesson Summary
Add to Add to Add to

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Log in or Sign up

Timeline
Autoplay
Autoplay
Speed

Recommended Lessons and Courses for You

Lesson Transcript
Instructor: Nicola McDougal

Nicky has taught a variety of chemistry courses at college level. Nicky has a PhD in Physical Chemistry.

We all know when we feel heat, but do you know how or when it was discovered? In this lesson, we learn about the revolutionary findings of James Prescott Joule who discovered how to get heat out of mechanical work.

What is Heat?

You have just made yourself a delicious hot cup of coffee. You put it on the table in front of you and wait for it to cool down. You can see the steam coming off the top and you can see it is clearly too hot to drink right now. The coffee cup may even be too hot to touch. If you measured the temperature of the coffee, it will be about 75 degrees centigrade and you know that is pretty hot. The room you are sitting in measures around 25 degrees centigrade, and over time, both the coffee cup and the coffee will cool down - soon it will be cool enough to drink.

Now, you also know if you don't drink all of your coffee, it continues to cool down to room temperature. Urgh cold coffee! So while you are waiting for you coffee to cool down, watch what is going on at the molecular level. The decreasing temperature of both the coffee and the cup are a sign that the average kinetic energy of the particles are decreasing - the molecules are slowing down. Both the coffee and the cup are losing energy. Energy is being transferred as heat to the surrounding air.

We can say that heat is simply the transfer of energy from a hot object to a colder object. Sounds simple, doesn't it? But, you may be surprised to learn that it wasn't until the middle 19th century that heat was understood in terms of energy.

Early Historical Views of Heat

Fire and heat has always fascinated man, and even in the old days, they knew that fire and heat were different. They noticed that after the fire had gone out, the embers still gave out heat. However, it took until the 1700s for scientists to start to explain what heat actually is. The Scottish chemist Joseph Black was the first modern chemist to explain heat. He noticed that a kettle filled with water and ice placed over a fire did not change temperature until all of the ice had melted. Black explained his observation by suggesting that heat flows like a liquid.

The famous French scientist Antoine Lavoisier took these observations a step further and developed the heat-fluid concept called the caloric theory. This theory described heat as a tasteless, odorless, invisible and weightless fluid, called a caloric fluid. It also stated that hot objects contain more of this fluid than cold objects. Caloric was also thought of as a weightless gas that could pass in and out of pores in solids and liquids. This was a commonly held theory until the end of the 18th century. But very soon this theory was challenged and later became obsolete.

Link Between Work and Heat

It was during the 19th century that the field of thermodynamics started to take off. And it was during this time that our understanding of work and energy developed. In 1843, the English physicist James Prescott Joule calculated the mechanical equivalent of heat in a series of experiments. His most famous piece of apparatus, now called the Joule apparatus, is shown here.

joule apparatus

To unlock this lesson you must be a Study.com Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use Study.com

Become a Study.com member and start learning now.
Become a Member  Back
What teachers are saying about Study.com
Try it risk-free for 30 days
Description

Earning College Credit

Did you know… We have over 160 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? Study.com has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Research Schools, Degrees & Careers

Get the unbiased info you need to find the right school.

Browse Articles By Category

Browse an area of study or degree level.

Recommended Articles
You are viewing lesson Lesson 8 in chapter 3 of the course:

 Back To Course

DSST Principles of Physical Science: Study Guide & Test Prep

21 chapters | 250 lessons | 14 flashcard sets

Ch 3. Thermodynamics in Physical Science
Ch 4. Waves and Optics

Mechanical Equivalent of Heat Related Study Materials

Create an account to start this course today
Try it risk-free for 30 days!
Create An Account

Explore our library of over 75,000 lessons

Browse by subject
Support