91Ó°ÊÓ

When you eat sugar \(\left(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\right)\), it is eventually converted into \(\mathrm{CO}_{2}\) and \(\mathrm{H}_{2} \mathrm{O}\), which you exhale. If you exhale onto a cold window, the window fogs up. (a) What chemical change is being mentioned here? (b) What physical change is being mentioned here? (c) \(\mathrm{CO}_{2}\) is a solid that sublimes at \(-78^{\circ} \mathrm{C}\). Temperatures on planet Earth almost never get this cold. What does that tell you about the fog on the window?

When a candle burns, the solid wax melts and burns. In the process, the wax is combined with oxygen from the atmosphere and converted into carbon dioxide and water vapor. Explain what is going on in terms of chemical change and physical change.

Gasoline can be thought of as having the formula \(\mathrm{C}_{8} \mathrm{H}_{18}\). When gasoline is used in a car's engine, it reacts with oxygen \(\left(\mathrm{O}_{2}\right)\). If you look closely at the exhaust pipe of a running car, you will see water dripping out of it. Where did this water come form (what kind of change is involved)?

When exposed to oxygen in the air, white phosphorus, \(\mathrm{P}_{4}\), catches fire and produces the compound \(\mathrm{P}_{4} \mathrm{O}_{10}\). Is this a description of a physical property or a chemical property of phosphorus? Explain.

Is the tarnishing of silver, Ag, a physical change or a chemical change? (The chemical formula for the tarnish on silver is \(\mathrm{Ag}_{2} \mathrm{~S}\).)

Nitrogen, \(\mathrm{N}_{2}\), combines with hydrogen, \(\mathrm{H}_{2}\), to give ammonia, \(\mathrm{NH}_{3}\). Nitrogen and hydrogen are odorless gases that are not very soluble in water. Ammonia is also a gas, but it has an extremely powerful odor and is very soluble in water. How can you explain this great difference in properties?

Suppose you wanted to explore the role of sunlight on plant growth. Explain what you would do to go through one cycle of the scientific method, including a prediction you might make.

Which of the following are elemental substances and which are compounds: diamond, a solid form of carbon, \(\mathrm{C}(s) ;\) liquid water, \(\mathrm{H}_{2} \mathrm{O}(l) ;\) nitric acid, \(\mathrm{HNO}_{3}(l)\); gaseous nitrogen, \(\mathrm{N}_{2}(g)\); liquid nitrogen, \(\mathrm{N}_{2}(l) ?\)

Classify each of the following as elemental substance, compound, or mixture: (a) Milk (b) Chocolate cake (c) Clean snow, \(\mathrm{H}_{2} \mathrm{O}(s)\) (d) The simple sugar fructose, \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\) (e) The mercury, \(\mathrm{Hg}\), in a thermometer

Match each symbol with the correct element name: (a) Na (b) Fe (c) Co (d) Sn (e) \(\mathrm{Mn}\) Possible names: neon, fermium, copper, mercury, cobalt, scandium, magnesium, phosphorus, manganese, iron, sodium, potassium, argon, tin, silver, gold, calcium.