Science fair project ideas??

depends on your grade

Explanation:

1.if u are a junior grader then a periscope will be great

2.for middle graders try making a vacuum cleaner with a plastic bottle

3.for high schoolers try something good and unique like a remote control car or u can also make one sonar just (a distance calculator of any object within 30cm of its reach) which i made in my high school science fair(for these projects learn arduino programming language)

or maybe try to think of something out of the box or ask other peoples

it is either c or d and i know for sure it is not a or b

all matter is made up of atoms

in any element all atoms are the same

elements in a compound are always in a constant ratio: apex