Answer:
1. zeroth --> Two objects in thermal equilibrium will have no net heat flow between them.
2. first --> Heat can change energy from one form to another, but the amount of energy in the universe is constant.
3. second --> The tendency of the universe is to increase entropy.
Explanation:
1. The zeroth law of thermodynamics states that:
"If object A is in thermal equilibrium (=same temperature) with object B, and object B is in thermal equilibrium with object C, then object A and object C are in thermal equilibrium as well". According to this, there is no heat flow between two objects in thermal equilibrium: in fact, two objects in thermal equilibrium have same temperature, so they have same thermal energy, therefore heat does not flow spontaneously from one object to the other. Heat flows spontaneously only if there is a temperature difference between the two objects.
2. The first law of thermodynamics states that:
"The variation of internal energy of a system is given by the sum between the heat absorbed by the system and the work done by the surrounding on the system itself". In formula:
where is the variation of internal energy of the system, Q is the heat absorbed by the system and W the work done by the environment on the system. A result of this law is that energy cannot be created nor destroyed, but only converted from one form to another.
3. The second law of thermodynamics states that:
"The total entropy of an isolated system can never decrease over time".
Entropy of a system is a measure of its degree of "disorder": the higher the entropy, the more disordered the system is. In nature, every system tends to go to a state of more entropy, and since the universe can be thought as an isolated system, the tendency of the universe is to increase its entropy.