Thermodynamics

You observe that carbon dioxide sublimes. Which of the following statements about the signs of this process is/are true? 

(I) Work (w) is positive. 

(II) Heat (q) is negative. 

(III) Change in Gibbs free energy (∆G) is positive. 

(IV) Change in entropy (∆S) is positive. 

1. II and III 

2. I only 

3. I and II 

4. I, II and III 

5. IV only 

6. III and IV

Compare between work and heat ?

If I heat some cold liquid water to To, do I increase its availability? 

A car engine takes atmospheric air in at 20°C, no fuel, and exhausts the air at – 20°C producing work in the process. What do the first and the second laws say about that?

An escalator raises a 200 lbm bucket of sand 30 ft in 1 minute. Determine the total amount of work done and the instantaneous rate of work during the process.

Consider the following specific heats: copper, 0.384 J/g·◦C; lead, 0.159 J/g·◦C; water, 4.18 J/g·◦C; glass, 0.502 J/g· ◦C. Which substance, once warmed, would be more likely to maintain its heat and keep you warm through a

long football game on a cold night? 

1. glass 

2. lead 

3. copper 

4. water

A battery is well insulated while being charged by 12.3 V at a current of 6 A. Take the battery as a control mass and find the instantaneous rate of work and the total work done over 4 hours.  

Differentiate between macroscopic and microscopic approaches. Which approach is used in the study of engineering thermodynamics.

Or 

Explain the macroscopic and microscopic point of view.

Calculate the height of a column of water equivalent to atmospheric pressure of 1bar if the water is at 150C. What is the height if the water is replaced by Mercury?

Which of the following statements concerning the first law of thermodynamics is/are true? 

(I) The internal energy of the universe is always increasing. 

(II) Internal energy lost by a system is always gained by the surroundings. 

(III) The universe is an isolated system. 

1. I only 

2. I and II only 

3. II and III only 

4. III only 

5. I and III only 

6. II only 7. I, II and III