Chemistry Ms. Piela Heat transfers in chemical reactions Energy Definition: The capacity to do...
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THERMOCHEMISTRY Chemistry Ms. Piela
Chemistry Ms. Piela Heat transfers in chemical reactions Energy Definition: The capacity to do work or supply heat Basic Types: Mechanical, Electrical,
Heat transfers in chemical reactions Energy Definition: The
capacity to do work or supply heat Basic Types: Mechanical,
Electrical, Potential, Kinetic
Slide 4
Energy that is stored within chemical bonds Determined by the
arrangement and bonding of atoms Examples: Gasoline, Food, etc
Slide 5
Exothermic processes (exits) Heat flows out of a system
Slide 6
System loses heat (negative sign) Examples: Explosions!, Sun,
Fire
Slide 7
Endothermic processes (enter) Heat is absorbed from
surroundings
Slide 8
System gains heat (positive sign), Heat change is > 0
Examples: Boiling water, ice melting
Slide 9
Energy transfers due to temperature differences between objects
Flows from hot to cold until temperature equilibrium is
reached
Slide 10
Energy cannot be created or destroyed, only transferred Can be
transformed Example: HeatMechanicalElectrical
Slide 11
Calorie (cal) the amount of heat needed to raise 1 gram of
water 1 C Heat calorie is not to be confused with dietary calories
1 dietary Calorie = 1 kcal = 1000 cal Joule (J) metric unit of heat
and energy Conversion Factor! Woo!
Slide 12
It takes 50.2 J to raise the temperature of a 100.0 g piece of
glass. How many calories is this?
Slide 13
A small chocolate bar has about 210,000 calories. How many
Joules is this?
Slide 14
The amount of heat required to raise 1 gram of a substance 1 C
Heat capacity is the amount of heat required to raise a substance 1
C
Slide 15
q = heat (J or cal) m = mass (g) C = specific heat T = Change
in Temp. ( C)
Slide 16
Specific heat plays a role in buffering climates Specific heat
of land = 0.8 J/g C Specific heat of water = 4.184 J/g C How does
this help buffer climates? Water heats up slower and cools down
slowly, releasing heat gradually
Slide 17
On the notes, youll see a table of specific heat capacities for
common metals. Well be using these throughout all the problems in
this section, so keep it handy!
Slide 18
A 1.55 g piece of stainless steel absorbs 141 J of heat when
its temperature increases by 178 C. What is the specific heat of
stainless steel?.511 J/g C
Slide 19
How much heat is required to raise the temperature of 250.0 g
of mercury from 52 C to 60 C? 280 J
Slide 20
If the initial temperature of a 10.0 g substance is 20.0 C and
100.0 J of heat are absorbed, what is the final temperature? The
specific heat of the substance is 1.15 J/g C. 28.7 C
