Chapter 1 - CHAPTER 1 KEYS TO THE STUDY OF CHEMISTRY Most...

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1-1 CHAPTER 1 KEYS TO THE STUDY OF CHEMISTRY Most numerical problems will have two answers, a “calculator” answer and a “true” answer. The calculator answer, as seen on a calculator, will have one or more additional significant figures. These extra digits are retained in all subsequent calculations to avoid intermediate rounding error. Rounding of a calculator answer to the correct number of significant figures gives the true (final) answer. 1.1 a) A shows a physical change. The substance changes from a solid to a gas. b) B shows a chemical change. Two diatomic elements form from a diatomic compound. c) Both A and B result in different physical properties. Physical and chemical changes result in different physical properties. d) B is a chemical change; therefore, it results in different chemical properties. e) A does result in a change in state. The substance changes from a solid to a gas. 1.2 Plan: Apply the definitions of the states of matter to a container. Next, apply these definitions to the examples. Solution: Gas molecules fill the entire container; the volume of a gas is the volume of the container. Solids and liquids have a definite volume. The volume of the container does not affect the volume of a solid or liquid. a) The helium fills the volume of the entire balloon. The addition or removal of helium will change the volume of a balloon. Helium is a gas . b) At room temperature, the mercury does no completely fill the thermometer. The surface of the liquid mercury indicates the temperature. c) The soup completely fills the bottom of the bowl, and it has a definite surface. The soup is a liquid , though it is possible that solid particles of food will be present. 1.3 a) gas b) solid c) solid 1.4 Plan: Define the terms and apply these definitions to the examples. Solution: Physical property – A characteristic shown by a substance itself, without interacting with or changing into other substances. Chemical property – A characteristic of a substance that appears as it interacts with, or transforms into, other substances. a) The change in color (yellow-green and silvery to white), and the change in physical state (gas and metal to crystals) are examples of physical properties . The change in the physical properties indicates that a chemical change occurred. Thus, the interaction between chlorine gas and sodium metal producing sodium chloride is an example of a chemical property . b) The sand and the iron are still present. Neither sand nor iron became something else. Colors along with magnetism are physical properties . No chemical changes took place, so there are no chemical properties to observe. 1.5 Physical Change – A change in which the physical form (or state) of a substance, but not its composition, is altered. Chemical Change – A change in which a substance is converted into a substance with different composition and properties.
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This note was uploaded on 07/30/2011 for the course CHEM 103 taught by Professor Lewis during the Spring '08 term at Wisc Eau Claire.

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Chapter 1 - CHAPTER 1 KEYS TO THE STUDY OF CHEMISTRY Most...

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