For each of the situations described below, the object considered is undergoing some changes. Among the possible changes you should consider are:
(Q) The object is absorbing or giving off heat.
(T) The object's temperature is changing.
(U) The object's internal energy is changing.
(W) The object is doing mechanical work or having work done on it.
(C) The objects chemical energy is changing.
For each of the situations described below, identify which of the four changes are taking place and write as many of the letters Q T U W C (or none) as are appropriate.
1. A cylinder with a piston on top contains a compressed gas and is sitting on a thermal reservoir (a large iron block). After everything has come to thermal equilibrium, the piston is moved upward somewhat (very slowly). The object to be considered is the gas in the cylinder.
Q T U W C
2. Consider the same cylinder as in part 1, but it is wrapped in styrofoam, a very good thermal insulator instead of sitting on a heat reservoir. The piston is pressed downward (again, very slowly), compressing the gas. The object to be considered is the gas in the cylinder.
Q T U W C
3. An ice cube sitting in the open air is melting.
Q T U W C
4. A mixture of two moles of hydrogen gas and one mole of oxygen gas in a thermally insulated vessel is subjected to small spark (contributing negligible energy) and converts to water vapor.
Q T U W C
Explain your reasoning for each of these cases.

In this exercise we have to have knowledge about thermodynamics in order to identify the alternatives that are correctly classified, so we can say that:

1.) QTUW

2.) UW

3.) QU

4.) QTUC

According to first law of thermodynamics:

Where:

1.) The first alternative corresponds to:

In other words QTUW.

2.) The second alternative corresponds to:

Work happen been finished ahead of the system. The pressure will without doubt deform the internal strength of bureaucracy:

In other words UW.

3.) The third alternative corresponds to:

The softening process begins cause the air coldness of some degree around the frozen water cubes happen warmer The complete frozen water particles take in heat strength from the warmer air, bestowing the piece energy and allowing to happen them to move out each one.

In other words QU.

4.) The fourth alternative corresponds to:

Chemical reaction maybe exothermic or endothermic that involves assimilation or release of heat. Since it happen commit small spark, skilled happen certainly a change in within strength.

In other words QTUC

See more about thermodynamics at link

1.) Q T U W 

Explanation:

1.) QTUW

2.) UW

3.) QU

4.) QTUC

According to first law of thermodynamics

dU = Q - W

Where

dU = change in internal energy

Q = heat added

W = work done by the system

2.) UW

Work is been done on the system. The pressure will surely distort the internal energy of the system

Pressure = Force/area.

3.) QU

The melting process begins because the air temperature around the ice cubes is warmer

The solid ice particles absorb heat energy from the warmer air, giving the particles energy and enabling them to move away from one another.

4.) Chemical reaction can be exothermic or endothermic which involves absorption or release of heat. Since it is subjected to small spark, there is definitely a change in internal energy.