Science 10
Brakke/Baier/Heathcote
Worksheet Thermochemistry I – Answer Key
Take the following notes from the powerpoint:
What is the difference between temperature and thermal energy?
ECA – Chemistry – Topic 01
What is a calorie?
What is a joule?
What is Calorimetry?
What is the difference between the system and the surroundings?
What is the difference between endothermic and exothermic?
The formulas (equations) for heat change are? (one uses ms, the other, c)
Water is a very common substance used in calorimetry, what is the specific heat of water as a liquid?
Where:
q=
s=
c=
m=
ΔT =
Example: Follow the example in the powerpoint below: How much heat is given off when an 869 g iron bar cools from 94 0C to 50C?
The specific heat of Fe is 0.444 J/g • 0C
What is enthalpy?
Draw an example of an endothermic and an exothermic process, include the equations and the value for ΔH:
Exothermic
Endothermic
Problems:
Show ALL work for these problems. Show a data table, the formula you are using, substituting into the formula,
with UNITS and then the answer.
No work = grade of 0.
Science 10
Brakke/Baier/Heathcote
ECA – Chemistry – Topic 01
1.
Calculate how much energy it takes to raise the temperature of 125 grams of aluminum from 100 to 245 degrees C. The
specific heat of aluminum is 0.900 J/g degree C
q=?
m=125g Al
s = 0.900 J/goc
ΔT = +145 oc
2.
Calculate the heat change needed to raise the temperature of 1000. g of water from 5.0 degrees C to 95.0 degrees C.
q=?
m = 1000 g H2O
s = 4.184 J/goc
ΔT = +90.0oc
3.
q = msΔT
10500 J = (520 g)( s )(218oc)
s = 0.0926 J/goc
Determine the specific heat of an unknown element if it takes 540 J to raise the temperature of 55.6 grams of this element
from 5.0 to 95.0 degrees C.
q = + 540 J
m = 55.6.g Cu
s = _______ J/goc
ΔT = + 90.0oc
7.
q = msΔT
q = (1000 g)(4.184 J/goc)(-90.0oc)
q = - 376,560 J
q = - 377 kJ (exothermic)
Determine the specific heat of copper if it takes 10 500 J of energy to raise 520.0 grams of it from 27.0 degrees C to 245.0
degrees C.
q = + 10,500 J
m = 520.g Cu
s = _______ J/goc
ΔT = + 218oc
6.
q = msΔT
q = (1000g)(4.184 J/goc)(90.0oc)
q = + 376,560 J
q = + 377 kJ (endothermic)
How much energy is given off by the water in question number two if the 1000. g of water cools from 95.0 to 5.0 degrees C?
q=?
m = 1000 g Al
s = 4.184 J/goc
ΔT = -90.0oc
4.
q=msΔT
q=(125g)(0.900 J/goc)(145oc)
q = 16,312.5 J
q = 16.3 kJ (endothermic)
q = msΔT
540 J = (55.6 g)( s )(90oc)
s = 0.1079 J/goc
If a reaction (chemical or physical) takes in heat energy we say it is ……endothermic……….., and the sign of q is …( + )….
If a reaction gives (chemical or physical) gives off heat energy we say it is …exothermic……., and the sign of q is …( - )…..