Chapter 1, Problem 1.92AE

From the information given in the following equations, classify each of the pure substances A through G as elements or compounds, or indicate that no such classification is possible because of insufficient information. a. A B + C b. D + E F + G

Which of the following represent physical properties or changes, and which represent chemical properties or changes? You curl your hair with a curling iron. You curl your hair by getting a “permanent wave” at the hair salon. Ice on your sidewalk melts when you put salt on it. A glass of water evaporates overnight when it is left on the bedside table. Your steak chars if the skillet is too hot. Alcohol feels cool when it is spilled on the skin. Alcohol ignites when a flame is brought near it. Baking powder causes biscuits to rise.

In the following description of the element iron, identify which of the properties are chemical and which are physical. Iron is rarely found as the free element in nature. Mostly it is found combined with oxygen in an ore. The metal itself can be obtained by reacting the ore with carbon, producing iron and carbon dioxide. Iron is a silver colored metal that conducts heat and electricity well. It is one of the most structurally important metals because of its hardness and mechanical strength, and it makes alloys with many other metals. Stainless steel is one useful alloy of iron that does not corrode in the presence of water and I oxygen, like pure iron does.

Suppose someone emptied ball bearings into a container of salt. Could you separate the ball bearings from the salt? How? Would your method involve no change, be a physical change, or be a chemical change?

Consider the photograph and illustrations of table salt. Do they include a model? Do they include a depiction of matter at the macroscopic, microscopic, and/or particulate levels? Explain your answers.

How do you distinguish (a) chemical properties from physical properties? (b) distillation from filtration? (c) a solute from a solution?

The following photo shows the element potassium reacting with water to from the element hydrogen, a gas, and a solution of the compound potassium hydroxide. (a) What states of matter are involved in the reaction? (b) Is the observed change chemical or physical? (c) What are the reactants in this reaction, and what are the produces? (d) What qualitative observations can be made concerning this reaction?

Which of the following are elements, and which are compounds? a NaOH; b BaCl2; c He; d Ag; e Fe2O3.

The following data refer to the element phosphorus. Classify each as a physical or a chemical property. (a) It exists in several forms, for example, white, black, and red phosphorus. (b) It is a solid at 25C and 1 atm. (c) It is insoluble in water. (d) It burns in chlorine to form phosphorus trichloride.