to cause the state of matter to change…. heat/energy needs to be….. added or removed
TRANSCRIPT
Endothermic versus Exothermic Example WS
Scenario Endo or Exo? Explain
1 Your car burns gasoline as you drivefrom home to school
Exothermic – “burning “ releases energy
2 Jerry is baking homemade bread inthe oven.
Endothermic – “baking” absorbs energy
3 The ice melts in your glass of water. Endothermic – “melting” absorbs energy
4 Sodium and chlorine combine in anexplosive reaction to form table salt.
Exothermic – “explosive” showsreleasing energy
5 Barry Balloon lights his candles to gethis hot air balloon to fly.
Exothermic – “lighting” candlesreleases energy
6. Water freezes on the pavement andthe roads become icy.
Exothermic – “freezing” releases energy
Endothermic versus Exothermic Example WSScenario Endo or Exo? Explain
7. Mom puts a pot of water on thestove and the water begins to boil
Endothermic – “boiling” absorbs energy
8. Water condenses on the side of yourglass of cold lemonade.
Exothermic - “condensation” releases energy
9. A glass of water left out overnightevaporates.
Endothermic – “evaporation” absorbs energy
10. A plant carries out photosynthesis. Endothermic- “photosynthesis” absorbs energy
11. A tree grows. Endothermic – “growing” absorbs energy
12. Sally gets really sweaty as she runs.Then she stops running and thesweat evaporates.(Hint: A 2-part question)
Exothermic- “sweat” giving off energyEndothermic – “evaporation” absorbs energy
Liquid gas : Vaporization
To cause this change…. heat/energy needs to be added
system heat
surroundings Hvap
Heat of vaporization
To cause this change…. heat/energy needs to be removed
Gas liquid : Condensation
system heat
surroundings Hcond
Heat of condensation
Vaporization Point(the temperature a liquid turns into a gas)
=
Condensation Point(the temperature a gas turns into a liquid)
Melting/Fusion is.. the vibrations in a solid are strong enough to… overcome attractions that keep solid atoms together
Solid liquid: Fusion
To cause this change…. heat/energy needs to be added
system heat
surroundings
Hfus
Heat of fusion
Liquid Solid: Solidification
To cause this change…. heat/energy needs to be removed
system heat
surroundings
Hsoli
d
Heat of solidification
Melting (Fusion) Point(the temperature a solid turns into a liquid)
= Solidification Point
(the temperature a liquid turns into a solid)
Heat of Physical Changes TableOn your note sheet: types of thermochem problems
SubstanceMelting
point°C
Heat of fusion(kJ/kg)
Heat of solidification
(kJ/kg) Boiling point
°C
Heat of vaporization
(kJ/kg)
Heat of condensation
(kJ/kg)
Helium -269.65 5.23 -5.23 -268.93 20.9 -20.9Hydrogen -259.31 58.6 -58.6 -252.89 452 -452Nitrogen -209.97 25.5 -25.5 -195.81 201 -201Oxygen -218.79 13.8 -13.8 -182.97 213 -213Ethyl alcohol -114 104.2 -104.2 78 854 -854
Mercury -39 11.8 -11.8 357 272 -272Water 0.00 334 -334 100.00 2256 -2256Sulfur 119 38.1 -38.1 444.60 326 -326Lead 327.3 24.5 -24.5 1750 871 -871Antimony 630.50 165 -165 1440 561 -561Silver 960.80 88.3 -88.3 2193 2336 -2336Gold 1063.00 64.5 -64.5 2660 1578 -1578Copper 1083 134 -134 2567 5069 -5069
When doing word problems….
1. Find the question word: determine what you are looking for. WANT
2. What #s did the problem give you GIVEN3. If only one # always start grid with that #
4. If Multiple #’s you NEED a formula
You forgot your glass of water outside. The next time you are outside, you realize your glass is empty. What happened?
Evaporation Vs Boiling• Both are Vaporization • Both allow liquid turn into a gas
BUT….• Evaporation is NOT Boiling
Evaporation
Explain how the following description is an analogy for evaporative cooling:
If the fastest runner is removed from a race, the resulting average speed of the
runners that remain will be lower.
Boiling Liquid has enough HEAT/ENERGY
to overcome the External Pressure
Vapor Pressure = External Pressure
Affect of Temp on Contained Liquid
KE of particles particle collisions VP
This why a tea kettle whistles
Elevation and Atmospheric Pressure↑ Elevation = ↓ Atmospheric Pressure
b/c less gas particles =less collisions = P
Sea Level more gas particles = more P
Pressure Cooker
Creates a High External Pressure
a bubble of vapor can’t form unless KE= T BP is = hotter liquid= shorter cooking time