Answer Happy

1. What is a chemical reaction? 2. When water boils on the stove, does a chemical change or a physical change take place? Explain your answer. 3. Give five examples that indicate a chemical change is probably occurring, 4. What does "Mn" above the arrow in an equation mean? 5. What symbol is used to indicate "produces" or "yields"? 6. Solid silicon and solid magnesium chloride form when silicon tetrachloride gas reacts with magnesium metal. Write a word equation, a formula equation, and a balanced chemical equation including all states of matter.

7. Magnesium oxide forms from magnesium metal and oxygen gas. Write a word equation, a formula equation and a balanced chemical equation including all states of matter 8. Describe evidence that burning gasoline in an engine is a chemical reaction. 9. Describe evidence that a chemical reaction takes place during a fireworks display. 10. The directions on a package of an epoxy glue say to mix small amounts of liquid from two separate tubes. Either liquid alone does not work as a glue. Should these liquids be considered reactants? Explain your answer. 11. When sulfur is heated until it melts and then is allowed to cool, beautiful yellow crystals form. How can you prove that this change is physical?

12. For each of the following equations, balance it and then write a sentence that describes the reactions, including the physical states and reaction conditions. a. Zn (s) + HCl(aq) → ZnCl2 (aq) + H₂(g) b. CaCl2 (aq) + Na2CO3 (aq) → CaCO3 (ppt) + NaCl (4) c. NaOH(aq) + HCl(aq) → NaCl (aq) + H20 m d. CaCO3(s) Cao (s) + CO2 (g)