a. iron ore - heterogeneous substance
(it contains a mixture of iron oxides)
b. quartz - homogeneous substance
(it is the crystalline silicon dioxide SiO₂, which is a very pure form of SiO₂)
c. granite - heterogeneous substance
(it as mixture of different oxides, mainly aluminium and silicon oxides)
d. energy drink - heterogeneous substance
(a mixture of water, sugar, carbon dioxide and different substances that may boost concentration, like caffeine)
e. oil-and-vinegar salad dressing - heterogeneous substance
(this salad dressing of oil and vinegar is composed of unsaturated triglycerides, acetic acid and water)
f. salt - homogeneous substance
(sodium chloride NaCl)
g. rainwater - homogeneous substance
(assuming the the atmosphere is clean, it is just pure water H₂O)
h. nitrogen - homogeneous substance
(it is the main component of air and it is a diatomic molecule N₂)
