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Chemistry Unit 2 – Text Assignments Assigned Reading and Problems are due on the day of the Unit Test on a separate piece of paper. The Unit Test will be on: _____________________ Core Topics Essential Knowledge Practice from HOLT Chemistry Topic 1: Atoms are made of three types of subatomic particles: protons, neutrons and electrons. Each atom has a nucleus in the center, made of protons and neutrons packed tightly together. An electron cloud surrounds the atomic nucleus. Read pg 79-86 – Subatomic Particles Elements and the Periodic Table A proton has a positive charge and a relative mass of one. The atomic number for an element is the same as the number of protons. All atoms of the same element have the same number of protons. An electron has a negative charge and a relative mass of zero. The number of electrons is the same as the number of protons in a neutral atom. Read pg 84 – Atomic Number is the Number of Protons of the Nucleus Do pg 86 – Practice Problems #1-4 A neutron has no charge and a relative mass of one. Topic 2: Compounds and Bonding Subscripts in a chemical formula represent the relative number of each type of atom. The subscript always follows the symbol for the element. The subscripts indicate the ratio elements (in terms of atoms or moles) in the compound. Parentheses are used when a subscript affects a group of atoms. Example: the formula for magnesium nitrate is written Mg(NO3)2 to show that there is a ratio of one magnesium atom, 2 nitrogen atoms and 6 oxygen atoms in the compound. Topic 3: Kinetic Theory Solids have a fixed shape. In a solid the particles are closely packed together. Each particle in a solid is held in one position and vibrates around that position. This results in a definite shape and volume. Read pg 24 – Compounds are Represented by Formulas Read pg 236 – Formulas Express Composition Read pg 378 – 380 – States of Matter The particles in a liquid stay relatively close together, but they can move around each other (rotate or tumble). This results in a definite volume but no definite shape. Gas particles are far apart; they move rapidly and collide with each other and with the walls of the container. This random motion results in no definite shape or volume. Topic 4: The Mole and Stoichiometry Phase changes (changes in physical state) occur when particles either speed up or slow down changing their relative motions. For a given substance, freezing and melting occur at the same temperature. Boiling and condensing also occur at the same temperature. For example, water both freezes and melts at 0oC (and both boils and condenses at 100 oC). Which phase change takes place depends on whether heat (energy) is being added or removed. Isotopes are atoms of the same element that have different numbers of neutrons. Some isotopes are radioactive, many are not Mass number of an individual isotope is the sum of the # of protons and the # of neutrons in an atom of that isotope. An element’s atomic mass, located on the Periodic Table, is a weighted average of the masses of all the known isotopes of the element. An element’s atomic mass represents the mass of one mole (6.02 x 1023 atoms) of the element and is called its molar mass. Be able to determine the number of moles for a given mass of an element. Topic 5: Chemical Reactions The chemical reaction where elements react (bond together) to form a compound is called synthesis. Example: Hydrogen gas and oxygen gas react to synthesize water. 2H2 + O2 2H2O The elements in a compound can only be separated by a chemical reaction. This reaction breaks the bonds between the elements resulting in decomposition. (Example: water decomposes to form hydrogen and oxygen gas. 2H2O 2H2 + O2 In both reactions, the rearrangement of atoms results in chemical bonds being broken and formed. Bond breaking requires energy while bond making releases energy Read pg 382 – 383 (Note the key terms highlighted) Do pg 384 – Problems # 1, 4, 6, 11, & 15. Read pg 84 – Mass Number is the Number of Particles in the Nucleus Read pg 88 – Isotopes of an Element Have the Same Atomic Number Read pg 230 – Amount in Moles Can Be Converted to Mass Do pg 89 – Problems # 1, 2, & 5 Read pg 277-278 – Synthesis Reactions Read pg 278-279 – Decomposition Reactions Topic 6: Solutions Topic 7: A solution is a homogeneous mixture because the separate parts of the mixture are distributed evenly and cannot be seen. The solvent (usually water) is the part of the solution that is present in largest amount. The solute is the substance that is dissolved in the solvent. Read pg 455 – Solutions are Stable Homogenous Mixtures Read pg 455 – Solution is a Broad Term A saturated solution has all the dissolved solute that it can hold, and can be identified by undissolved solute particles on the bottom after mixing. An unsaturated solution can still hold more solute. Read pg 474 – Saturation Identify equipment: ring stand, funnel, watch glass, beaker, graduated cylinder and evaporating dish. Read pg 17 – Density Can be Used to Identify Substances Demonstrate filtration and evaporation and explain when each can be used to physically separate a mixture. Define filtrate as the liquid that passes through the filter. Do pg 31 – Problem # 8 Do pg 477 – Problem # 7 Experimentation Measure volume of a liquid in milliliters (mL) using a graduated cylinder and stating measured digits plus the estimated digit. Be sure to read the bottom of the meniscus of the liquid. Measure mass in grams (g) using an electronic balance and identifying the estimated digit. Determine the density of solids and liquids experimentally and with the proper number of significant digits. When multiplying and dividing the least number of significant figures is the number you use in your answer.