10. Which of the following is an example of the formation of a mixture? A. Rust forming on an iron nail. C. Sodium and chlorine forming table salt. B. Sugar crystals dissolving in water. D. Hydrogen and oxygen reacting to produce oxygen. 11. Water (H2O), is not found on the periodic table because water is a... A. atom B. liquid C. mixture D. compound 12. When the elements copper (Cu) and oxygen (O) chemically combine, they form... A. an ion C. a compound D. a mixture B. a gas a 13. Which one of the following statements about compounds is correct? A. At least one of the elements in a mixture must be a gas. B. The elements in a compound are always present in the same ratio. C. The properties of a compound are the same as the properties of the elements of which it is made up. D. It is easy to separate a compound into the elements that it is made from. 14. A beaker containing a black-yellow powder has a magnet put into it. When the magnet is removed, black particles are stuck to it, leaving a yellow powder behind in the beaker. The black-yellow powder is therefore A. a mixture B. a compound C. an element D. an atom a 15. Which of the following is not a compound? A. HCI B. CI C. NaCl D. CO2 16. How many elements are represented in the compound? Na2CO3 A. 1 B. 2 C.3 D. 4 17. Arrange the following elements according to their increasing atomic number 1. Hydrogen (H) II. Sodium (Na) III. Selenium IV. Iodine A. I, IV, II, II B. I, II, III, IV C. IV, II, I, III D. I, III, II, IV 18. Metals, nonmetals, and metalloids are characteristic properties of: A. Substances B. Compounds C. Alloys D. Elements 19. Naturally occurring elements are B. 92 C. 99 a. 82 D. above 100 by now 20. Brass is an example of an/a A. Alloy B. Compound C. Mixture D. Element​