How is the Periodic Table helpful to scientists?

Because it helps predict the types of chemical reactions that a particular element is likely to participate in by telling each element's atomic number and usually its atomic weight

Explanation:

what is the general relationship between a galaxy's distance from earth and its speed?

the answer is:

the farther away a galaxy is from us, the faster it is moving away from us.

answer: enthalpy

explanation:

for a exothermic reaction, the energy is released i.e. the energy of the products is lower than the energy of the reactants.

= enthaply

= energy of products

= energy of reactants

as , thus comes out to be negative. negative value of enthalpy shows that the reaction is exothermic.