Question: maree has recently purchased a new chest deep freezer for...
Maree has recently purchased a new chest (deep) freezer for keeping food at the very low temperature
Maree is interested in determining how long it will take some foods to freeze and how long it will
take some foods to thaw.
a Maree understands that her new freezer can lower the temperature of food at a rate of 6°C per hour.
Maree places some food, currently at a room temperature of 24°C in her new freezer. How long
will it take for the food to reach the freezer temperature of –18°C?
b On a different day, Maree discovered that a loaf of bread only took four hours to freeze to the
temperature of –18°C. What was the room temperature on this day?
c Maree wishes to determine the rate at which frozen meat can thaw and return to a temperature of
5°C ready for her to cook. She carries out the following test cases:
(Note the below is a table, columns separated with / sign)
Size of frozen meat /Room temperature/ Time to reach 5°C
3 kilograms/ 12°C/ 4 hours
1 kilogram/ 16°C/ 55 minutes
2 kilograms/ 10°C/ 2 hours and 20 minutes
1 kilogram/ 22°C/ 40 minutes
Based on Maree’s test cases, what is an average time for how long it takes food to thaw (and reach
5°C) per kilogram of frozen meat for a normal room temperature of 15°C?
d If Maree has a 4 kg frozen turkey in the freezer that she wishes to start cooking at 4:30 p.m., and
she estimates the average room temperature during the day will be 19°C, what time would you
suggest Maree takes the turkey out of the freezer?
e If Maree has an n kg frozen piece of meat that she wishes to cook in t hours and the room
temperature is 15°C, when should Maree take the meat out of the freezer? Your answer will be an
expression in terms of t and n.