catalyst 1.if you have 2000 g of water and you heat it up from 10 o c to 70 o c, then what is the...
TRANSCRIPT
Catalyst
End
100 oC Water Burn 100 oC Steam Burn
Justify – TPS• Why is it worse to be burnt by 100 oC steam
than 100 oC water? Justify your answer with Word Wall vocab!
Lecture 7.4 – Latent Heats
Today’s Learning Target• 7.7 – I can use the latent heat of phase change
to calculate the amount of energy that is released or absorbed during a change of phase.
What are Latent Heats?
I. ΔHfusion and ΔHvaporization
• There is energy required to change phases• ΔHfusion = Energy to change solid to a liquid.
• ΔHvaporization = Energy to change liquid to a gas.
• ΔHfreezing = Energy to change liquid to a solid
• ΔHcondensation = Energy to change gas to a liquid
II. Latent Heat• Can calculate the amount of energy needed to
convert a substance from one phase to another• Latent Heat – The energy absorbed as a
substance changes phases
ΔH of vaporization/condensation
ΔH of fusion/freezing
Latent Heats
How do you calculate latent heats?
I. Equation for Latent Heat
• m = mass of compound• ΔH = Enthalpy values for phase changes
(constants)• Easy way to remember: Q equals maH! (The delta
kinda looks like an A!)
Class Example
• You have a 2000 kg of ethanol. Calculate the energy you would need to turn solid aluminum into liquid. The ΔHfusion is 109 kJ/kg.
Table Talk• You have 6342 kg of mercury. How much energy
would be required to take mercury from liquid to a gas? The ΔHvaporization is 294 kJ/kg
Stop and Jot
• You have an ice cube of H2O that weighs 2000 kg and you melt it to liquid. How much energy does that require? The ΔHfusion is 334 kJ/kg.
SUMMARIZE
Checklist Manifesto!• How do I know which equation to use?Does it have specific heat?
Then use calorimetry!Does it give you ΔH or ΔT
If ΔH then use q = mΔHIf ΔT then use q = m x Cp x ΔT
Box the one it’s asking you to find!Plug in the right numbers and solve!
Connect 4
• Begin working on your “Homework 7.3”• There will be an exit slip after this activity
Work Time
Learning Log AssessmentRate yourself 1 – 4 on LTs 7.1-7.7
1. You have 2000 g of water that is heated from 25 C to 100 C. What is the heat absorbed by this process. The specific heat of water is 4.184 J/(gxC)
Exit Slip
Learning Log AssessmentRate yourself 1 – 4 on LTs 7.7
• Test Thursday/Friday!
Closing Time