What is an indication that a chemical reaction took place?

Abar magnet cut in half will form a total ofpoles.a)fourb)eightc)two

Which composition of water moves to begin a deepwater current?

Does the distance travelled by an oscillating mass between times t=0 and t2 equal the displacement of the particle over the same time period if t2> t/2? hint: consider a sine wave starting at t1=0, then consider a closing wave starting at t1=0, for your explanation.