Question

Proof is defined as _ _ _ _ _ the percentage by volume of alcohol in ethanol-water mixture.
a.) twice
b.) thrice
c.) half
d.) four times

Answer 1

Hint: The word proof in alcohols means the amount of ethanol present in an ethanol-water mixture. The proof is usually the double of the percentage of ethanol in ethanol- water mixture. If the ethanol is 20 % then the proof would be 40 % for this solution.

Complete answer:
> The word proof does not mean here the evidence. It has a different meaning and there is even historical background about how it came into use. So, the word proof can be defined as the double the amount of alcohol content present by volume in alcohol water mixture.
Example :- If we have whisky containing 80 % alcohol and 20 % water; then it will be called as 160 % proof.
> The word was started being used in the 16th century in England. In those times, there were no standards to measure the content of alcohol in alcohol water solution. So, this was started as the proof or evidence for the quality of alcohol.
> The test was that alcohol was allowed to burn. If it burned, then the alcohol was called as above proof and in case it did not burn then it was called as under proof. So, it was a burn or no burn test.
> After this even one more method arose on similar principles called gunpowder method. In this, the gunpowder was soaked in spirit and then it was allowed to burn. If it could then it was called as above proof and if not then under proof.
So, these two methods gave rise to the term proof.
> Even now, on some of the bottles the word proof is written.
> So, we can conclude that proof can be defined as twice the percentage by volume of alcohol in ethanol-water mixture.

Thus, option a.) is the correct answer.

Note: It must be noted that proof in actual is the double in percentage as the volume of alcohol in alcohol-water mixture. The word above proof and under proof were used at that time in the 16th century. Now, the exact value of proof is used if required sometimes.