Hey there!
Chemical changes are changes in object's chemical compounds and chemical compositions, and often can't be reversed.
Here's an example:
If you have a piece of paper and you happen to burn it, that can't be reversed.
In other words, it can't be "un-burned". Nothing can restore it to its previous state.
Hopefully this helped!
Tin
Chemical Element
Tin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Wikipedia
Symbol: Sn
Electron configuration: [Kr] 4d105s25p2
Atomic number: 50
Melting point: 449.5°F (231.9°C)
Atomic mass: 118.71 u
Boiling point: 4,717°F (2,603°C)
Electrons per shell: 2, 8, 18, 18, 4
Density is defined as the ratio of mass and volume. The formula of density is:
-(1)
Density of milk = 
(given)
Volume of milk = 
(given)
Substituting the values in formula (1):
Hence, the mass of the milk is 
.
Atomic radius- a measure of the size of its atoms, usually the mean or typical distance from the center of the nucleus to the boundary of the surrounding cloud of electrons.
Electron Affinity-the electron affinityof an atom or molecule is defined as the amount of energy released or spent when an electron is added to a neutral atom or molecule in the gaseous state to form a negative ion.
Electronegativity-a measure of the tendency of an atom to attract a bonding pair of electrons. The Pauling scale is the most commonly used. Fluorine (the most electronegative element) is assigned a value of 4.0, and values range down to caesium and francium which are the least electronegative at 0.7.
Lonization energy- qualitatively defined as the amount of energy required to remove the most loosely bound electron, the valence electron, of an isolated gaseous atom to form a cation.
For a and b, you need to divide it by Avogadro’s number to find the answer.
a. (6.022x10^23)/6.022x10^23 = 1 mole of Ne
b. (3.011x10^23)/6.022x10^23 = 0.5 moles of Mg
For c and d, you’ll use the mass provided divided by the molar mass to find the number of moles.
Pb molar mass = 207.2 g/mol
c. (3.25x10^5)/207.2 = 1.57x10^3 moles of Pb
For d, I can’t tell if is Cu, C or something else but you can follow the steps above to solve the problem.
