Answer
a. physical
b. chemical
c. physical
d. physical
Work Step by Step
a. physical: Density is a physical property of a substance.
b. chemical: Hydrogen gas reacting with oxygen to form water is a chemical reaction and is a chemical property of that substance.
c. physical: The boiling point of a substance is a physical property.
d. physical: The conduction of electricity is a physical property of a substance.