All Concepts
Which material would you use to heat up your food on a stove and why?
Aluminum 0.900 J/g C
Brass 0.380 J/g C
Copper 0.387 J/g C
Steel 0.120 J/g C
Steel. Lowest Specific heat. It can absorb and transfer energy fast.
How much heat energy (in Joules) is required to raise the temperature of a 50.0 gram sample of water from 20.0∘C to 35.0∘C?
(water specific heat is 4.184 J/g C
3135 J
In calorimetry, this is why one side of the equation is negative and the other is positive:
-m1c1(Tf-Ti)1 = m2c2(Tf-Ti)2
One substance is releasing energy, one side is absorbing energy
36.00 g of ice at 0 °C is melted into liquid water. The molar heat of fusion of water is 6.01 kJ/mol. (1 mol of water = 18.02 g) How much heat is required?
12.0 kJ
What are the two regions of a heating curve where temperature does not change?
During phase changes — melting (solid → liquid) and boiling (liquid → gas).
Imagine you have 10 grams of iron (c=0.45 J/g⋅°C) and 10 grams of glass (c=0.84 J/g⋅°C). If you put both substances under the same heat lamp for five minutes, which material will have a higher final temperature, and why?
Iron. It takes less energy to raise the temp. 1°C
A 25.0-gram piece of an unknown metal absorbs 1,000 Joules of heat, causing its temperature to rise from 25.0∘C to 125.0∘C. What is the specific heat of the metal in J/g∘C?
0.400 J/g∘C
A 590 g brass sample at 98.0 C is dropped into 2800 g of water at 5.0 C. If the temperature of the mixture is 6.8 C, what is the specific heat of brass?
What is 0.392 J/g C?
27.00 g of water at 100 °C is cooled to ice at 0 °C.
(1 mol=18.02 g)
How much heat is released?
Use:
cwater=4.18 J/goC
ΔHfus=6.01 kJ/mol
20.3 kJ
Substance X and Y are different materials. Both have the same mass. The same amount of energy is put into them.
Substance X has a final temp of 30C. Substance Y has a final temp of 60C. Which one has the lower specific heat and why?
Substance Y. It took the same amount of energy and the final temperature was higher.
Why does it take more energy to vaporize 1 gram of water than to melt 1 gram of ice?
Because molecular attractions are completely broken during vaporization, requiring more energy than simply weaking them during melting.
A 15.0-gram sample of gold (c=0.129 J/g∘C) at an initial temperature of 95.0∘C loses 40.0 Joules of heat to the surroundings. What is the final temperature of the gold?
74.3∘C
A 75.0-gram piece of metal is heated to 100.0∘C and then placed into a cup containing 50.0 g of water at 22.0∘C. If the final temperature of the metal and water mixture is 28.8∘C, what is the specific heat of the unknown metal?
0.266 J/g∘C
How much heat is required to complete this process:
27.00 g of ice at 0.00 °C is heated to steam at 100.00 °C.
Use:
cwater=4.18 J/goC,
ΔHfus=334 J/g,
ΔHvap=2260 J/g
81,320 J
81.32 kJ
45.00 g of water at 25.0 °C is heated to 100.0 °C. How much heat is absorbed?
Specific heat of water = 4.18 J/g°C.
14,100 J
Decide if each describes an endothermic or exothermic process:
a. This type of process absorbs heat from the surroundings, making the temperature drop.
b. When water freezes into ice, heat is released to the surroundings. This makes freezing an example of this type of process.
c. Melting, boiling, and evaporating are all examples of this type of process.
d. In this type of process, potential energy of the products is lower than that of the reactants.
e. A cold pack used for sports injuries undergoes this type of reaction when activated because it absorbs heat from your skin.
a. Endothermic
b. Exothermic
c. Endothermic
d. Exothermic
e. Endothermic
3000 g gold bar (c=0.129 J/g∘C) at 99 C is dropped into water and had a final temp of 47C. What is the energy that is absorbed by the water?
What is 20124J?
Mass of metal: 215 g
Mass of water: 285 g
Initial temperature of water (and calorimeter): 12.6 °C
Initial temperature of metal: 99.1 °C
Final equilibrium temperature: 18.6 °C
(Note: calorimeter mass & heat capacity may be given: e.g., 132 g with specific heat 920 J/kg·°C)
Use this to calculate: the specific heat of the metal.
0.41 J/goC
13.50 g of ice at -10 °C is heated to water at 100 °C. The sample is not vaporized. How much total heat is absorbed?
Use:
cice=2.09 J/goC
cwater=4.18 J/goC
ΔHfus=6.01 kJ/mol
10.43 kJ
You place 100 g of copper at 80°C into a fixed amount of water. You then repeat the experiment with 200 g of copper at 80°C in the same amount of water. Which experiment (the 100 g or 200 g copper) results in a higher final equilibrium temperature, and why?
200g. More mass at the same temp means more energy will be transferred to the water.
If 1.0 g of ice at 0°C is heated until it becomes steam at 100°C, list all the steps (in order) and which formula applies at each step.
1️⃣ Melt ice → q = m x Hf
2️⃣ Heat liquid → q = m x Cwater x ΔT
3️⃣ Boil liquid → q = m x Hv
A 2000. gram piece of lead is heated from 80.00 to 100.00 Celcius using 5120 J of energy. The specific heat capacity of lead is _______________
What is 0.128 J/g C?
A 240-gram chunk of carbon (ccarbon=0.72 J/g∘C) is heated to 215∘C and quickly placed into 275 grams of water at 12∘C. Assuming a perfectly insulated system, what will the final temperature (Tf) of the mixture be?
38.5∘C
36.00 g of water at 50 °C is cooled to ice at -10 °C. How much total heat is released? (1 mol water = 18.02 g)
Use:
cice=2.09 J/goC
cwater=4.18 J/goC
ΔHfus=6.01 kJ/mol
20.29 kJ
50.00 g of steam at 100 °C is condensed to liquid water at 25 °C. (1 mol water =18.02 g). How much total heat is released?
Use:
cwater=4.18 J/goC
ΔHvap=40.68 kJ/mol
128.48 kJ