Specific heat Concepts
What did each variable represent in q=mc(Tf-Ti)?
q=energy
m=mass
c= specific heat
Tf = final temp
Ti = initial temp
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
What measurement(s) did we take in the calorimetry experiment?
The temperature of the water.
The mass of the water.
The mass of the food.
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
True or false
A substance with high specific heat will be resistant to temperature change when energy is added
True
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
What was the function of the coffee can part of the calorimeter?
The coffee can was used to prevent the heat/energy from escaping away from the water
The specific heat of water is much higher than that of sand or soil. Use this concept to explain why coastal cities (like San Francisco or Hawaii) have much milder temperature swings between day and night and summer and winter, compared to inland areas (like the desert).
The high specific heat means it won't absorb heat as much, nor will it release heat as readily.
Substance X and Y are different materials. Both have the same mass. Both start out at 25degreesC. The same amount of energy is put into them.
Substance X has a final temp of 30degreesC. Substance Y has a final temp of 60degreesC. Which one has the lower specific heat and why?
Substance Y. It took the same amount of energy and the final temperature was higher.
A 15.0-gram sample of gold (c=0.129 J/g∘C) at an initial temperature of 95.0∘C gains 40.0 Joules of heat to the surroundings. What is the final temperature of the gold?
115.7C
What was the function of the hinged strainer part of the calorimeter?
To give the flame around the food access to oxygen so it could continue to combust.
When firefighters are trying to cool down a large structure fire, why is water or foam the preferred medium over other common cooling liquids (like vegetable oil or ethanol, which have lower specific heat values)?
Water has a high specific heat and would not heat up as fast
Oil and Ethanol have lower specific heats and would absorb energy quicker. (they are also highly flammable)
When two objects mix together, will their temperatures be similar or different? Why?
Similar because you have created a mixture. That mixture will go through thermal equilibrium and have the same temperature throghout
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?
BONUS: There was 8000g of water and it also had a final temperature of 47C, what was its initial temp?
What is 20,124J?
BONUS 47.6012189293C
What data is needed to calculate the energy content of food in our bomb calorimeter?
Initial temp of the water.
Final temp of the water.
The difference in mass of the food as a result of burning.
(mass and specific heat of the water)
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.
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.
or
Aluminum. It absorbs a lot of heat before transfering any to your food, so the food won't burn as soon.
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 75.0-gram piece of dried banana is burned in the calorimeter and raises the water temperature of 200 g of water 18 degrees. The piece weighs 2 grams after its flame goes out. How much energy per gram does the dried banana have?
BONUS
206.334 Joules / gram
.049 Vanity Calories / gram
49.32 lab calories / gram
15,062.4 Joules of energy entered the water (and left the hunk of banana). 73 grams of banana provided the energy.
A typical cooking pot has a thin metal body (low c) and a thick ceramic or plastic handle (high c and low conductivity). Explain why the body of the pot and the handle require materials with different thermal properties to function effectively.
Low Specific means better heat absorption and transmittance for cooking. A high specific heat handle is so you can grab the pot