When an equation is balanced what is the same on both side?

Iknow the answer to 13 is b and 14 is d. i just need to know why the correct answers are correct

After watching the video "zinc strip in copper nitrate solution", and reading the instructions, click on the link labeled "start" just below the drawing of the pencil tip. follow the direction to complete the 3x3 grid. answer the below questions for the portion of the activity in which sn(s) is placed in agno3(aq)

Which is an example of the practical pursuit of alchemy? a. forming perfect substances. b. transforming base metals. c. developing metalworking techniques. d. linking spiritual characteristics with material substances.