Q1 - Only nuclear reactions change the identity of an element, since they work with the element nucleus which is the atom's part that involves the number of protons in it. The protons define what element we are using in the reaction.
Q2- Rate of condensation = rate of evaporation, since water is in liquid form and the two possible transformations that can happen without changing the flask's temperature are condensation and evaporation. There is no solid form involved to cause precipitation and we don't calculate the moles based on the state the molecules are presented like liquid and vapor.
Q3- Solid phase of matter has a definite shape and volume, since the molecules are arranged in a specific way, close to each other and without much movement possibilities.
Q4- Exothermic, since the reaction involves heat liberation, which characterizes exothermic reactions.
Q5 - Acid feel slippery is not a true consideration when talking about acids' properties. This property would be true to bases, which explains the soapy feeling when it degrades fats into soap.
Q6- It increases the average of kinetic energy and number of collisions per minute, because it gives kinetic energy to the molecules involved in the process, making them move faster and collide more to each other.
Q7- [H3O+]=[OH-] , since those are the ions in water molecules. When combined, they form H2O, the pure water form.
Q8- Gamma rays can penetrate your body the deepest, since they are very energized and short-wavenlenghted. These properties make it easier for them to penetrate into your body.
Q9 - K, because it lost one electron due to the ionic bond that is being formed in the product KCl.
Q10- The products are at a lower energy level than the reactants, since energy is lost during the reaction through heat liberation (exothermic reactions liberate heat to the surroundings).
Q11 - MgCl2, since a salt is composed by two inorganic elements.