Asubstance that speeds up the rate of a chemical reaction is called
a. a catalyst
b. a substrate.
c. an enzyme.
d. both a and c

Ionic compounds are made of ions, and yet the overall charge of an ionic compound is neutral. why?

There is one girl i like and i don't know how to tell her that, i have a feeling she knows but if she doesn't i don't want to make a fool out of myself how is one way to boost my confidence on asking her out

Which change to the system wood cause the freely-moving piston to lower?