Physical changes only affect the appearance of an object. While chemical happens to the chemical make up and cannot be reversed. Think of it this way- physical change is like hair tint , it wears off- chemical is like permanent hair dye, it's permanent.
The last one/D (my answer has to be at least 20 characters so idk it is what it is)
Answer:
Sodium chloride, commonly known as salt, is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions.
Explanation:
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Answer: The partial pressure of the Kr is 320 mm Hg.
Explanation:
According to Raoult's Law , the partial pressure of each component in the solution is equal to the total pressure multiplied by its mole fraction. It is mathematically expressed as
where, 
= partial pressure of component A
= mole fraction of A
= total pressure
mole fraction of Krypton = 
Thus partial pressure of the Kr is 320 mm Hg
Answer: The geologic time scale is the “calendar” for events in Earth history. It subdivides all time into named units of abstract time called—in descending order of duration—eons, eras, periods, epochs, and ages.
Explanation: I learned about it the other day
