Answer: The answers are:
The number of protons in an atom of an element is unique to each element.
A proton in an atom of one element is identical to a proton in an atom of another element.
Explanation: The number of protons in an atom of an element is unique to each element. The number of protons in an atom of an element is the atomic number of that element. Atomic number determines the chemical properties and reactivity of the atom.
All atoms are made up of three particles: protons, electrons and neutrons. These particles are identical in all the elements, what distinguishes one element from another is the number of each of these particles it contains. Therefore, a proton in an atom of one element is identical to a proton in an atom of another element likewise the electrons and neutrons.
Answer: 
Explanation:
where,
= boiling point of solution = ?
= boiling point of solvent (X) = 
= freezing point constant = 
m = molality
i = Van't Hoff factor = 1 (for non-electrolyte like urea)
= mass of solute (urea) = 29.82 g
= mass of solvent (X) = 500.0 g
= molar mass of solute (urea) = 60 g/mol
Now put all the given values in the above formula, we get:
Therefore, the freezing point of solution is 
Developing a theory would be a successful outcome<span />
Given parameters:
Heat of fusion of water = 334j/g
Mass of ice = 45g
Temperature of ice = 0.0°c
Unknown:
Amount of heat needed to melt = ?
Solution:
This is simply a phase change and a latent heat is required in this process.
To solve this problem; use the mathematical expression below;
H = mL
where m is the mass
L is the heat of fusion of water;
H = 45 x 334 = 15030J
