1. If we use symbol U_sys to represent theenergy (also referred as internal energy) contained in the system,what is a reasonable symbol to represent the energy of thesurroundings? Provide an expression relating the total energy ofthe Universe, U_univ to the energy of the systemand energy of the surroundings? Explain your answer

2. Now consider the system undergoes a process, letDU_sys represent the change in system’s energy,DU_univ represents the change in energy of the universe.Provide an expression for DU_univ in terms of energychange of the system and the surrounding. Explain your answer.

3. Consider your answer in (2), what would be the reasonablesign for DU_univ? Explain.

4. Consider your answer in (2), what would be the reasonablesign for DU_sys? Explain

5. Let q and w represent two ways to exchangeenergy between system and surrounding. What is a reasonableexpression that relates the internal energy change DU_syswith q and w?

6. Consider burning of propane gas (propane and oxygen gases areour interested system), is this an exothermic reaction? What is thesign of q? what is the sign of DU_sys ? Describe in yourown words what happened to the internal energy of the system?

7. Identify each energy exchange as heat or work and determinethe sign of heat or work is positive or negative

(a) An ice cube melts and cools the surrounding beverages (icecube is the system here)

(b) A metal cylinder is rolled up a ramp (the metal cylinder isthe system)

(c) Steam condenses on skin causing a burn (the condensing steamis the system)

8. Consider a closed container that contains some hydrogen gas(H₂) and oxygen gas (O₂). These gases reacted(burned) and formed water vapor.

(a) Write a balanced chemical equation to represent this process(reaction)

(b) Do you expect this is an exothermic or endothermic reaction?What is the sign of q?

(c)What is the sign of internal energy change DU for thisreaction?

(d) List the types of energy stored in the system before andafter reactions. How do you explain the sign of internal energy DUobserved in part (c)?