The density would decrease because the mass of an object deals with the amount of atoms in the object and since none of the object was reduced "a" wouldn't be the answer. Depending on the amount and period of time that the heat is applied the liquid could change into a gas so "d" wouldn't be correct. Density is the mass÷ volume, and when you add heat to an object it could take up different amounts of space because of its particles gaining energy and spreading apart. So the density would decrease because of the volume increasing. So I believe that "c" is the answer.
Answer: option A) initially increases, then decreases.
Justification:
The increase of the rate of effective collisions among particles as the temperature increases is explained by the collision theory in virtue of the increase of the kinetic energy.
This is, as the temperature increase so the kinetic energy increase and the higher the kinetic energy the greater the number of collisions and the greater the chances that this energy overcome the activation energy (the energy needed to start the reaction).
Now, as the reaction progress the number of reactants particles naturally decrease (some of them have been converted into product) so this lower number of particles means lower concentration which means lower collisions and, thereafter, a decrease in the reaction rate.
When both particles, the electron and the proton move at the same speed, they may have differences with their de Broglie wavelength, the particle that would have a longer wavelength would be the proton since the wavelength is in direct proportionality with the mass of the particle.
Measuring density: Measure the mass (in grams) of each mineral sample available to you. The mass of each sample is measured using a balance or electronic scale. Record mass on a chart.