IN Class Lecture Practice Problems for Energy- You will need your book and the specific heat chart on page 73!
1. Convert from one unit to the other- You must use dimensional analysis & Use SIG FIGS!
f. 20.0 calories to Joules
a. 1.69 J to cal
d. 68 calories to kilocalories
c. 820.1 J to kilocalories
m. 9.806 kJ to cal
o. 5467.9 kcal to kJ
2. Determine the temperature change when:
a. 20.0 g of water is heated from 16.8 °C to 39.2 °C.
b. 35.0 g of water is cooled from 56.5 °C to 5.9 °C.
3. Use the equation Q=smΔt to answer the following questions
a) Determine the energy required (in J) when the temperature of 3.21 grams of liquid water increases by 4.0 °C.
b) Determine the energy needed (in J) when 55.6 grams of water at 43.2 °C is heated to 78.1 °C.
c) Determine the energy required (in kilojoules) when cooling 456.2 grams of water at 89.2 °C to a final temperature of 5.9 °C.
6. Determine the energy required to:
- Raise the temp of 4.56 grams of aluminum at -15.0 °C to 78.0 °C
- Cool the temp of 4.56 grams of iron from 200.0°C to 20.0 °C
- Raise the temp of 4.56 grams of gold from 37.5°C to 98.2°C
- Cool the temp of 4.56 grams of Silver from 79.5°C to 15.0 °C
If you can do this- You got it!
What is the specific heat of 49.7 grams of a substance has a temp change of 57.0 °C with 5.08 KJ?
How much energy in KJ will it take to turn 37.0 grams of ice at -5.05 °F to 120.00 °C? Realize that there are different specific heats for different states of matter!
Sugar has a specific heat of 0.25J/gC. What will be the temperature change of 3000.0 grams of sugar if you add 57.0 Kj of energy to it?
Solutions:
Selections from Question One
a) 1.69 J / (4.184 J/cal) =
b) 0.3587 J / (4.184 J/cal) =
c) 820.1 J / (1000 J/kJ) = 0.8201 kJ
d) 68 cal x (4.184 J/cal) =
e) 423 cal / (1000 cal/kcal) - 0.423 kcal
f) 20.0 cal x (4.184 J/cal) =
m) 9.806 kJ x (1000 J/kJ) = 9806 J
o) 5467.9 kcal --> 5467900 cal x (4.184 J/cal) =
3. q = (3.21 g) (4.0 °C) (4.184 J g¯1 °C¯1)
4. q = (55.6 g) (34.9 °C) (4.184 J g¯1 °C¯1). How did I know this was liquid water?
5. Same type as #4, but no answer. Good luck!!