Document 9-5 PHYSICS Heat Formula and Conservation\" Homework Assignment Name: S

Question

Document 9-5 PHYSICS Heat Formula and Conservation" Homework Assignment Name: SHOW ALL OF YOUR WORK 1) Duing lab a 300 watt immersion heater is used to heat up 250 g of water placed inside a 120 g aluminum [c- 2 calig·?] calorimeter, all initially at 25"C FYI: A calorimeter is a lightweight insulated flask used to isolate an experiment from its surroundings; the calorimeter, however, does warm up and as a result must be taken into account in any calculations. (a) If the immersion heater is used for 2.5 minutes, how many heat calories will be made available during this time ? 1.a) (b) Determine the final temperature T, of the water once the 2.5 minutes of heating are completed. 1.b), 2.) To deternine the specific heat capacity of a metal, the following lab procedure is followed: Into a Styrofoam cup is poured 400 g of 17'C water Into a beaker is poured 110 g of water and 276 g of the metal. The contents of the beaker are then heated to a temperature of 88 C Once the beaker's contents have been poured into the Styrofoam cup, the final temperature of the mixture is measured to be 36 C Write down the necessary conservation of energy equation and then solve for the metal's specific heat capacity. 2. 3.) A 150 g glass beaker e- 2 calgCcontaining 200 g of water (all at 66 C) is placed into a freezer How much energy will have transferred to the freezer compartment before the beaker's content has cooled to 12? ?

Explanation / Answer

1.

a)

P = power of the rod = 300 Watt

t = time of usage = 2.5 min = 2.5 x 60 sec = 150 sec

Heat calories made available is given as

Q = P t = 300 x 150 = 45000 J = 10755.3 cal

b)

Tf = final temperature

Ti = initial tempeature of water and aluminium = 25 c

cw = specific heat of water = 1

mw = mass of water = 250 g

ca = specific heat of aluminium = 0.2

ma = mass of aluminum = 120 g

Using the equation

Q = mw cw (Tf - Ti) + ma ca (Tf - Ti)

10755.3 = (250) (1) (Tf - 25) + (120) (0.2) (Tf - 25)

Tf = 64.3

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