7 Easy Questions Physic I need them in 3 hours.

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I'll attach the questions in a file, they are easy and short. I need them in 3 hours, because it is due tonight.

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1)At 20°C, a brass cube has an edge length of 28 cm. What is the increase in the cube's surface area when it is heated from 20°C to 70°C? The linear expansion coefficient of brass is 19 × 10-6 /C°. 2) A certain diet doctor encourages people to diet by drinking ice water. His theory is that the body must burn off enough fat to raise the temperature of the water from 0.00°C to the body temperature of 37.0°C. How many liters of ice water would have to be consumed to burn off 440 g (about 0.970 lb) of fat, assuming that this much fat burning each gram of fat requires 7.71 Cal be transferred to the ice water? (One liter = 10-3m3. The density of water is 1.00 g/cm3.) 3) Calculate the minimum amount of energy, in joules, required to completely melt 100 g of silver initially at 45.0°C. The melting point of silver is at 962°C. Its specific heat capacity is 236 J/kg·K and its latent heat of fusion is 105 kJ/kg. 4) How much water remains unfrozen after 49.7 kJ is transferred as heat from 244 g of liquid water initially at its freezing point? The latent heat of fusion is 333 kJ/kg. 5) An insulated Thermos contains 140 cm3 of hot coffee at 77.0°C. You put in a 19.0 g ice cube at its melting point to cool the coffee. By how many degrees has your coffee cooled once the ice has melted and equilibrium is reached? Treat the coffee as though it were pure water and neglect energy exchanges with the environment. The specific heat of water is 4186 J/kg·K. The latent heat of fusion is 333 kJ/kg. The density of water is 1.00 g/cm3. 6) Ethyl alcohol has a boiling point of 78.0 ˚C, a freezing point of -114 ˚C, a heat of vaporization of 879 kJ/kg, a heat of fusion of 109 kJ/kg, and a specific heat of 2.43 kJ/kg·K. How much energy must be removed from 0.553 kg of ethyl alcohol that is initially a gas at 78.0 ˚C so that it becomes a solid at -114 ˚C? 7) Suppose 400 J of work is done on a system and 54.0 cal is extracted from the system as heat. In the sense of the first law of thermodynamics, what are the values (including algebraic signs) of (a) W, (b) Q, and (c) ΔEint?
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Explanation & Answer

Hi, please see the following solution. It took me a little ling because I checked the answers first before handing them in.

1)At 20°C, a brass cube has an edge length of 28 cm. What is the increase in the
cube's surface area when it is heated from 20°C to 70°C? The linear expansion
coefficient of brass is 19 × 10-6 /C°.
SOLUTION:
∆L = Lα∆T
∆L = (28 cm) × (19 × 10-6 /C°) × (70oC – 20oC) = 0.0266 cm = 2.66 × 10-2 cm
Original surface area = 6s2 = 6(28 cm)2 = 4704 cm2
New surface area = 6(28 + 2.66 x 10-2 cm)2 = 4712.94 cm2
Increase in surface area = 4712.94 cm2 – 4704 cm2 = 8.94 cm2
2) A certain diet doctor encourages people to diet by drinking ice water. His theory is
that the body must burn off enough fat to raise the temperature of t...


Anonymous
Just what I needed…Fantastic!

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