A(2)    Argon is the correct answer.  Argon is an element, which by definition, cannot be broken down by a chemical reaction.

(4) is the correct answer.  Charge, energy, and mass are all conserved.

According to the laws of conservation, mass, charge, and energy are conserved in a reaction.  While, the energy may be transferred to the environment (in this case an exothermic reaction), or the charge may be transferred to another atom, these factors are conserved, not lost in the reaction.

Answer 1 is correct.

The elements K, Cl, and O are combined in a ratio of 1:1:3.  This ratio is fixed because it is required for the compound to keep its identity of Potassium Chlorate. 
Answers 3 and 4 are incorrect because potassium chlorate is composed of only 3 elements, Potassium, Chlorine, and Oxygen.

(1)    Compound is the correct answer.

Because they are a mixture of various atoms, they cannot be the same element, but rather a set formula of atoms with the same properties, which is also known as a compound.

(1)    Is the correct answer.

In a physical change, reactants change into another physical state.  In answer one, the sample of water changes from a solid to a liquid form, when heat is added.  In the other options, the samples do not change from the gaseous state.

(1)    Is the correct answer. (ethanoic acid)

By looking at Table H, we can see that the vapor pressure of ethanoic acid is much lower than the other samples.  In this case, the vapor pressure of ethanoic acid is approximately 22 kPa.

(4) vaporization is the correct answer.
As substances are vaporized, they carry heat with the vapor into the air.  This is a form of potential energy.

(2)    Is the correct answer.

At STP, equal volumes of gases will have equal molecules.  In this case, 5 liters of two gases will contain the same the same number of molecules.