1. Warm-up Unit 7 Test Scores will be in PowerSchool this afternoon
Make-up tests need to be completed this week.
Test Corrections
Pink Slips this week
Everyone else next week
Pick up the four handouts at the front & a calculator.
Highlight important dates on your new Unit Calendar
Write your Name and “Unit 8” on your new Warm-up sheet.

2. Phase Changes

3. Phase Diagram
Shows the stable phase of a substance at any given temperature and pressure

4. Phase Change
At constant pressure, a phase change (change in state) always involves a change in heat energy
During a phase change, the temperature remains constant! All of the heat energy that is added is being used to overcome intermolecular forces

5. Math Time!
We can calculate the amount of heat that is needed to change the state of a given amount of a substance using the following equations:
𝐪=𝐦 𝐇 𝐯 (vaporization)
𝐪=𝐦 𝐇 𝐟 (melting)
𝐪=𝐦 𝐇 𝐬𝐨𝐥𝐧 (dissolving)
Variables:
q = amount of heat
m = mass of substance
Hv = heat of vaporization (liquid to gas)
Hf = heat of fusion (solid to liquid)
Hsoln = heat of solution (solid to aqueous)

6. Quick Note
When heat is released from a system, we show this as a negative amount of heat. Just flip the sign of the equations you already know!
𝐪=−𝐦 𝐇 𝐯 (condensation)
𝐪=−𝐦 𝐇 𝐟 (freezing)
𝐪=−𝐦 𝐇 𝐬𝐨𝐥𝐧 (undissolving)

7. Practice!
The heat of fusion for water is 334 J/g. Calculate how much energy must be removed to completely freeze 1600 g of water.

8. Practice!
The heat of vaporization for oxygen is J/g. Calculate how much heat must be released to condense kg of oxygen gas to liquid oxygen.

9. Practice!
How many kilojoules of heat are required to vaporize 54.0 g of ethanol (CH3CH2OH) if Hv for ethanol is 946 J/g?

10. Practice!
What mass of water can be evaporated by adding 32 kJ of heat? Hv for water is kJ/g.

11. Warm-Up What is the stable phase of CO2 at 5 atm and -80 oC?
At what pressure and temperature can you find the triple point of CO2?

12. Warm-up Turn in your homework: Specific Heat Practice
Read the Objectives, Materials & Equipment, and Proceedures for todays lab.

13. Water Phase Change Lab Start hot plate immediately! (Step 3)
Little hot plate set to 9
Yellow hot plate set to high
Blue/Gray hot plate set to 300°C
ABOUT 100 mL of water! Ask me for ice. (Step 1)
Thermal Equilibrium (Step 2)
CLEAN UP
Turn hot plate OFF!
Be careful with hot beaker! Wait for it to cool!
Place used beaker upside-down in drying rack!

14. Warm-Up What is the normal melting point of water?
If you have an ice-water mixture at the normal melting point, and you begin to increase the pressure while keeping the temperature constant, what will happen?