An 850 W consumer coffee maker can make 10 cups (1.75 liters) of 80 °C coffee from 20 °C tapwater in 10 minutes. What percentage of the electric energy consumed actually makes it to the coffee?
A 100 g cube of aluminum is removed from a bath of boiling water and dropped in a bath of room temperature water (2.00 liters at 20.0 °C). What is the final temperature of the water and zinc assuming heat loss to the surroundings is negligible?
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numerical
An ordinary thermometer consits of 25 g of glass and 2 g of ethyl alcohol. If it has an initial temperature of 22 °C, what temperature will it read when it is completely submerged in 100 g of 80 °C water?
Large chicken egg (65.9 g)
A perfectly cooked egg in the shell should reach a final temperature of 63 °C. If you don't have access to an immersion heater (a.k.a. a sous vide) it should be placed in boiling hot water, but not in boiling water. Once the cooking water starts boiling, the heat should be turned off, the egg submerged, and the pot covered. When both the cooking water and the egg are at 63 °C it is ready to eat. Determine the minimum mass of water needed to accomplish this task if…
the egg was removed from a refrigerator at 4 °C and cooked in New York City where the boiling point of water is 100 °C
the egg was removed from a pantry at 22 °C and cooked in the south of France where the boiling point of water is 100 °C
the egg was removed from a hen house at 15 °C and cooked in the Himalayas where the boiling point of water is 82 °C
When fish are harvested on a commercial scale they are often dressed (headed, gutted, scaled, and sometimes even skinned, deboned, and fileted) and then frozen at sea (FAS). Packaged, individually quick frozen (IQF) seafood is what consumers usually buy since it makes it easier for them to take what out what they need for the day and keep the rest frozen for later use. Block frozen seafood, on the other hand, is normally meant for industrial users who prefer to receive product in bulk form. When block frozen fish arrive at a processing plant they are sometimes too cold to be dealt with. Fish that is warmed slightly but still kept frozen is said to be tempered to distinguish it from fish that has been completely thawed or defrosted.
A tightly packed block of frozen pollock fillets is to be turned into breaded fish sticks — or fish fingers, if you prefer. A conveyor-belt-fed, microwave-powered "tempering tunnel" will be used to temper the fish before it is sawed into sticks or fingers.
Answer the following questions given the information in the table below, the text of this problem, and your knowledge of physics. (As a first approximation, assume that frozen pollock is made entirely of water ice.)
Converting a block of frozen fish into breaded fish sticks
quantity
value
mass of frozen block
25
kg
temperature during shipping and storage
−18
°C
temperature before tempering
−14
°C
temperature after tempering
−4
°C
microwave generator frequency
975
MHz
microwave generator power, rated
75
kW
microwave generator power, maximum
100
kW
tempering tunnel efficiency
27
%
tempering tunnel length
4.57
m
frying oil (canola) temperature
200
°C
number of sticks or fingers per block
378
length
11.45
± 0.5 cm
temperature during shipping and storage
−18
°C
How long should the block spend in the tempering cavity if it is set to…
25 kW
30 kW
At what speed should the conveyor belt move the block through the microwave warmer if it is set to…
