Chemistry Praxis Study Questions and Answers

Intensive property A physical property of a substance that is not dependent on the size of mass of a sample, and cannot be determined by looking at the substance. Ex: density, mp, bp, temperature. Extensive property A physical property that depends on the amount of matter in a sample. Ex: mass, volume. Chemical property How a substance will change when it reacts with other substances and changes its chemical identity. Ex: flammability, oxidation state, toxicity. Periodic table -Arranged by increasing atomic number. First organized by weight by Demitri Mendeleev. -mass number is a weighted average of all isotopes -rows are periods and columns are groups Metals -makes up majority of elements -hard, shiny, ductile, malleable, good conductors, form alloys, all solid except mercury. -extend from left side of periodic table to almost far right side. Nonmetals -do not conduct electricity -brittle -more volatile (lower mp and bp and are found as gases at room temp) -right side of periodic table Metalloids -have both metal and nonmetal characteristics -semiconductors -in between metals and nonmetals on periodic table Alkali metals Group 1, s block. Soft, silvery, and react violently with water to form bases. Halogens Group 17, p block. Poisonous and used in common household cleaners. "salt-forming": forms salts once reacting with metals Noble Gases Group 18, p block. Colorless, odorless, and unreactive. Valence energy levels The greater the period number, the higher the energy level. That valence electron is farther from the nucleus and has more energy to react.