Chapter 1, Problem 1.9E

Which of the following are chemical changes? Which are physical changes? a. the cutting of food b. interaction of food with saliva and digestive enzymes c. proteins being broken down into amino acids d. complex sugars being broken down into simple sugars e. making maple syrup by heating maple sap to remove water through evaporation f. DNA unwinding

Classify each of the following as (1) a physical property, (2) a physical change, (3) a chemical property, or (4) a chemical change. a. the process of burning a piece of newspaper b. the fact that metallic copper reacts with chlorine gas c. the process of melting ice d. the fact that metallic gold is a solid at room temperature

All of the following processes involve a separation of either a mixture into substances or a compound into elements. For each, decide whether a physical process or a chemical reaction is required. a Sodium metal is obtained from the substance sodium chloride. b Iron filings are separated from sand by using a magnet. c Sugar crystals are separated from a sugar syrup by evaporation of water. d Fine crystals of silver chloride are separated from a suspension of the crystals in water. e Copper is produced when zinc metal is placed in a solution of copper(II) sulfate, a compound.

In the accompanying photo, you see a crystal of the mineral calcite surrounded by piles of calcium and carbon, two of the elements that combine to make the mineral. (The other element combined in calcite is oxygen.) Based on the photo, describe some of the physical properties of the elements and the mineral. Are any properties the same? Are any properties different? Calcite (the transparent, cube-like crystal) and two of its constituent elements, calcium (chips) and carbon (black grains). The calcium chips are covered with a thin film of calcium oxide.

In the following description of the element bromine, identify which of the properties are chemical and which are physical. Bromine is one of the few elements that is a liquid at room temperature. It is an acrid-smelling substance that reacts readily with most metals. It evaporates easily, so most containers of bromine are filled with visible amounts of red fumes. Most bromine is obtained from sodium bromide, a compound found in salt beds.

The following pairs of substances represent heterogeneous mixtures. For each pair, describe the steps you would follow to separate the components and collect them. a. wood sawdust and sand b. sugar and sand c. iron filings and sand d. sand soaked with oil

Identify each physical property and physical change mentioned in each of these statements. Also identify the qualitative and the quantitative information given in each statement. (a) The blue chemical compound azulene melts at 99 C. (b) The white crystals of table salt are cubic. (c) A sample of lead has a mass of 0.123 g and melts at 327 C. (d) Ethanol is a colorless liquid that vaporizes easily; it boils at 78 C and its density at 20 C is 0.789 g/mL.

In each case, describe the change as a chemical or physical change. Give a reason for your choice. (a) A cup of household bleach changes the color of your favorite T-shirt from purple to pink. (b) The fuels in the space shuttle (hydrogen and oxygen) combine to give water and provide the energy to lift the shuttle into space. (c) An ice cube in your glass of lemonade melts.

The following are properties of substances. Decide whether each is a physical property or a chemical property. a Chlorine gas liquefies at 35C under normal pressure. b Hydrogen burns in chlorine gas. c Bromine melts at 7.2C. d Lithium is a soft, silvery-colored metal. e Iron rusts in an atmosphere of moist air.