1. lead (pb), silver (ag), and iron (fe) are examples of which of the following?

a. elements

b. molecules

c. compounds

d. all the above

2. elements can be broken down into simpler substances.

true
false

3. a substance made up of only atoms of one type is called a(n)

a. particle

b. molecule

c. element

d. compound

4. the most common element in the universe is

a. neon

b. oxygen

c. hydrogen

d. boron

5. no two elements are exactly alike.

true
false

How is electrolysis most commonly used to produce an energy source? a - splitting water molecules produces oxygen, which organisms breathe to fuel their bodies. b - splitting water molecules produces hydrogen gas, which is used to power machines through hydrogen fuel cells. c - splitting carbon dioxide molecules produces coal, a form of carbon that can be burned to produce heat. d - splitting carbon dioxide molecules produces natural gas, which can be burned to generate electricity in power plants.