1. Temperature Energy and Heat
CHAPTER 3
Temperature Energy and Heat
3.1 Temperature

2. Why is temperature important in chemistry?
What is temperature?
Why is temperature important in chemistry?
How is energy related to temperature?
Have students try to define temperature in their own words. Words such as “hot” and “cold” will probably come up.
In previous chapters, we have seen how the temperature increases the rate at which sugar dissolves in water. That is one example of how temperature is important in chemistry.
When water molecules collide with sugar molecules, they transfer energy. This was mentioned in the previous chapter.
Section 3.1 will go into these ideas in greater detail (ex: kinetic energy)

3. Milk fat particles are being pushed around by water molecules

4. Milk fat particles are being pushed around by water molecules
At room temperature, atoms and molecules are in constant motion
Brownian motion

5. Grains of sand stand still…

6. Grains of sand stand still…
… but the individual atoms are in constant, random motion.
kinetic energy: the energy of motion.
temperature: a measure of the average kinetic energy of atoms or molecules.

7. Random motion
Non random motion
Random motion
AFFECTS
temperature
Non random motion
DOES NOT AFFECT
temperature

8. Temperature is an average
Some molecules have more kinetic energy than the average.
Some molecules have less kinetic energy than the average.
Temperature is the measure of the average kinetic energy of atoms or molecules
Slower
(less energy)
Faster
(more energy)

9. Temperature is an average
Some molecules have more kinetic energy than the average.
Some molecules have less kinetic energy than the average.
Temperature is the measure of the average kinetic energy of atoms or molecules

10. Does everyone express temperature the same way?
Some of your students might come / be familiar with a country where temperatures are measured in oC.
Using oC and oF, invite students to describe how hot a summer day might be, and how cold a winter night might be.

11. Temperature scales

12. Temperature scales
Water boils
Water freezes
How can we go back and forth between the two scales?

13. What temperature in Celsius is the same as 100oC?

14. What temperature in Celsius is the same as 100oF?
Asked: Temperature in oC
Given: 100oF
Relationships:

15. What temperature in Celsius is the same as 100oF?
Asked: Temperature in oC
Given: 100oF
Relationships:
Solve:
Answer: 100oF is the same temperature as 37.8oC

16. What is the Fahrenheit equivalent of 15oC?
Asked: Temperature in oF
Given: 15oC
Relationships:

17. What is the Fahrenheit equivalent of 15oC?
Asked: Temperature in oF
Given: 15oC
Relationships:
Solve:
Answer: 15oC is the same temperature as 59oF.

18. How can we accurately measure temperature?
Hot or cold?
What feels hot to one person might just be warm to another.
How can we accurately measure temperature?

19. All thermometers are based on a physical property that changes with temperature.
Thermal expansion:
Mercury thermometers
Alcohol thermometers
Electrical sensors:
Thermistor
Thermocouple

20. The temperature probe in the Lab-Master uses a thermistor
All thermometers are based on a physical property that changes with temperature.
Thermal expansion:
Mercury thermometers
Alcohol thermometers
Electrical sensors:
Thermistor
Thermocouple
The temperature probe in the Lab-Master uses a thermistor

21. kinetic energy: the energy of motion.
temperature: a measure of the average kinetic energy of atoms or molecules.

22. What happens when the temperature is really, really low?
What is the lowest possible temperature?
You would theoretically reach a point where atoms are no longer in motion (zero kinetic energy).
This would happen at absolute zero (0 kelvin) which is introduced in the next slide.
kinetic energy: the energy of motion.
temperature: a measure of the average kinetic energy of atoms or molecules.

23. Absolute zero At absolute zero the kinetic energy is essentially zero.
3 different scales

24. Unit conversion
We have already seen:

25. Unit conversion
+ 273
- 273

26. Unit conversion
Convert 27oC into kelvins.

27. Unit conversion Convert 27oC into kelvins.
Asked: Temperature in kelvin
Given: 27oC
Relationships:

28. Unit conversion Convert 27oC into kelvins.
Asked: Temperature in kelvin
Given: 27oC
Relationships:
Solve:
Answer: 300 K is the same temperature as 27oC.

29. Three temperature scales:
Molecules are in constant, random motion.
This affects temperature.
Three temperature scales: