13. Which of the following materials is a pure substance?
a. cement
b. aluminum foil
c. petroleum
d. brine
14. What are the elements present in a table salt (NaCl)?
a. Sodium and Krypton
c. Sodium and Magnesium
b. Sodium and Chlorine
d. Sodium and Manganese
15. It is a combination of atoms which can be separated using chemical processes. a. Element
c. Electrolysis
b. Compounds
d. Homogeneous mixture
16. Some symbols of the elements like iron and silver are taken from their ancient names. What are their symbols? A. I and S
b. In and Sr
c. Fe and Ag
d. Hg and Pb​