1. An aluminum rod is 18.5 cm long at 20°C and has a mass of 350 g. If 11,500 J

Question

1. An aluminum rod is 18.5 cm long at 20°C and has a mass of 350 g. If 11,500 J of energy is added to the rod by heat, what is the change in length of the rod?

2. Lead pellets, each of mass 1.10 g, are heated to 200°C. How many pellets must be added to 540 g of water that is initially at 20.0°C to make the equilibrium temperature 25.0°C? Neglect any energy transfer to or from the container.

3. A 51-g ice cube at 0°C is heated until 43 g has become water at 100°C and 8.0 g has become steam at 100°C. How much energy was added to accomplish the transformation?

4. A thermopane window consists of two glass panes, each 0.50 cm thick, with a 1.0-cm-thick sealed layer of air in between. (Use 0.8 J/s · m · °C for the thermal conductivity of glass and 0.0234 J/s · m · °C for the thermal conductivity of air to answer the following.)

(4a) If the inside surface temperature is 24.0°C and the outside surface temperature is 0.0°C, determine the rate of energy transfer through 1.50 m2 of the window.

(4b) Compare your answer to (a) with the rate of energy transfer through 1.50 m2 of a single 1.0-cm-thick pane of glass. Disregard surface air layers.

Explanation / Answer

Q1.

first calculate how hot the bar gets

U = c·m·T
U is energy in Joules to heat the material by T
c is specific heat of the material in J/kg·K
m is mass in kg, T is temperature change in ºC
specific heat of Aluminum is 900 J/kgC

11.5kJ = 900 J/kgC x 0.35 kg x T
T = 36.5º

now how much length changes
L/L = T, is linear thermal expansion coef
linear thermal expansion coef Al 24e-6 /K
L = 0.185 x 24e-6 x 36.5 = 0.000162 meter

Please post other questions separately.

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