Heat and temperature (article) | Khan Academy
The main difference between heat and temperature is heat is the overall energy of the molecular motion, whereas temperature is the average. The zeroth law of thermodynamics says that no heat is transferred between two objects in thermal equilibrium; therefore, Relationship between heat and temperature Heat capacity: Converting between heat and change in temperature. The relationship between heat and temperature change is usually expressed in the form shown below where c is the specific heat. The relationship does not.
The water molecules in a cup of hot coffee have a higher average kinetic energy than the water molecules in a cup of iced tea, which also means they are moving at a higher velocity.
Changes of Phase (or State)
Temperature is also an intensive property, which means that the temperature doesn't change no matter how much of a substance you have as long as it is all at the same temperature! On an atomic level, the molecules in each object are constantly in motion and colliding with each other.
Every time molecules collide, kinetic energy can be transferred. When the two systems are in contact, heat will be transferred through molecular collisions from the hotter system to the cooler system. The thermal energy will flow in that direction until the two objects are at the same temperature.
Heat and temperature
When the two systems in contact are at the same temperature, we say they are in thermal equilibrium. Zeroth law of thermodynamics: Defining thermal equilibrium The zeroth law of thermodynamics defines thermal equilibrium within an isolated system.
The zeroth law says when two objects at thermal equilibrium are in contact, there is no net heat transfer between the objects; therefore, they are the same temperature. Another way to state the zeroth law is to say that if two objects are both separately in thermal equilibrium with a third object, then they are in thermal equilibrium with each other.
The zeroth law allows us to measure the temperature of objects. Any time we use a thermometer, we are using the zeroth law of thermodynamics.
How does Temperature Differ from Heat?
If heat is coming into a substance during a phase change, then this energy is used to break the bonds between the molecules of the substance.
The example we will use here is ice melting into water. Immediately after the molecular bonds in the ice are broken the molecules are moving vibrating at the same average speed as before, so their average kinetic energy remains the same, and, thus, their Kelvin temperature remains the same.
Below is a picture of solid ice melting into liquid water. The molecule of ice and the molecule of water the black balls are moving with the same rate of vibration in this diagram. This is meant to show that they have the same average speed and thus the same average kinetic energy since they have the same mass and thus the same Kelvin temperature. The motions are, though, greatly exaggerated. Actually, the motions of the molecules should be considered tiny vibrations.
What is the relationship between heat and temperature? - ppt download
At the moment of melting the average kinetic energy of the molecules does not change. The heat is used to break the bonds between the ice molecules as they turn into a liquid phase. Since the average kinetic energy of the molecules does not change at the moment of melting, the temperature of the molecules does not change.
Since both the ice and the water molecules have the same average kinetic energy at the time of melting, the temperatures of both are the same. Click this button to see the computer code for this animation.
Here's the code that runs the above animation. You can change the code, if you like, and then click the following 'Reevaluate code' button.
The program will then work as per your changes. Of course, your changes, especially random changes, can introduce errors, miscalculations, and browser crashes. If you need to get things back to their original condition, just reload this page using your browser's reload button.
The intention here is to conveniently show the inner workings of this program so that you understand how the diagram is drawn.
Can you figure out how to change the code to make the molecules vibrate at a higher frequency? Click the 'Code' button again to close this section.
When heat is added to the ice these bonds are broken and the ice melts.
The molecules afterward bond to one another with less strength and a different geometry, and water is formed. Now, before the melting, the molecules were actually moving when in the solid state.