PS Spring Final Study Guide Answers

Ch. 16 Objectives Describe how the chemical energy in fossil fuels is converted into electrical energy. Chemical potential energy in fossil fuels is burned, releases thermal energy, thermal energy reacts with water to form steam, steam turns a turbine, turbine spins a generator/transformer, energy sent to consumers through power lines Some energy is lost along the way in the form of heat Discuss nuclear fusion as a possible energy source. Fusion = combining of hydrogen atoms into helium Not useful because it requires high temperatures to occur, high temps are hard to maintain, ends up using more energy than it makes

Analyze the need for alternative energy sources. Fossil fuels are nonrenewable and will run out at some point Harmful to the atmosphere, releasing CO2, Describe alternate methods for generating electricity. Burn fossil fuels, Burn biomass, Nuclear power, solar, hydroelectric, windmills, geothermal, tidal energy

Ch. 18 Objectives Define pure substances and mixtures. Pure substance – type of matter with fixed/definite composition, all the atoms are the same, element & compound Mixture – 2 or more substances that can be separated by physical means Identify elements and compounds. Elements – pure substances in which all atoms have the same identity Compounds – 2 or more different elements combine in a fixed proportion

Compare and contrast physical and chemical changes. Physical changes – doesn’t change the identity, sometimes its reversible Chemical changes – changes the identity, creates something new Determine how the law of conservation of mass applies to chemical changes. Law = mass is neither created nor destroyed Mass stays the same

Ch. 19 Objectives Identify the names and symbols of common elements. Use periodic table Oxygen = O, Carbon = C, hydrogen = H, Ne = Neon, Ti = Titanium, B = Boron, Al = Aluminum Describe the electron cloud model of the atom. Area around the nucleus is where electrons are likely to be found, electrons move so quickly it is hard to pinpoint their location Current model of the atom

Compute the mass number of an atom. Protons + Neutrons = mass number Average Atomic Mass = look on the periodic table Identify the components of isotopes. Atoms of the same element (same # of protons) with different number of neutrons (changes the mass #) Most elements have more than 1 isotope

Use the periodic table to obtain information. Periodic table = arrangement of elements Developed by Mendeleev Can obtain = atomic weight, atomic number (# of protons), group and period, chemical symbol, state of matter, name, Explain what metals, nonmetals and semi-metals are and where they are located on the periodic table. Metals = left side of table, shiny, good conductors, solid Nonmetals = right side of table, brittle, poor conductors, most are gases Semi-metals/metalloids = found on staircase, properties of metals and nonmetals

Ch. 22 Objectives Describe how a compound differs from its component elements. Different chemical and physical properties NaCl = safe to eat, Na = reacts violently with water, Cl = toxic gas Discuss why chemical bonding occurs. Elements form bonds to achieve stability Gain, lose, or share electrons to be stable Stable # of electrons = 8 (Outer shell/valence electrons) Noble gases = don’t form compounds readily because they have a full valence shell of 8 electrons

Describe ionic and covalent bonds. Ionic = when ions attract due to their opposite charges Ions, good conductors, gain or lose electrons = ions Metal & nonmetal Covalent = when atoms share electrons to form a molecule 2 nonmetal

Write formulas and names for ionic compounds. Name of Positive ion name of negative with –ide at the end Sodium chloride Ammonium hydroxide When naming transition metals, you must determine their charge and indicate that using roman numerals (Ex. Copper (I) oxide) K3P = potassium phosphide

Write formulas and names for covalent compounds. USE GREEK PREFIXES Prefix-Name of Positive ion prefix-name of negative with –ide at the end H2O = dihydrogen monoxide Carbon tetrafluoride = CF4

Ch. 23 Objectives Identify the reactants and products in a chemical reaction. Reactants = compounds/elements that are put together, left side Products = compounds/elements made, right side Determine how a chemical reaction satisfies the law of conservation of matter. Everything is equal Same # of atoms of each element on each side

Using coefficients, balance chemical equations. Coefficients = big numbers, precede symbols and formulas to indicate number of that compound or element Identify the general types of chemical reactions. Decomposition – one reactant breaks down into 2+ products, AB  A + B Synthesis – A + B  AB, 2+ reactions combine to form 1 product Single-Replacement – one element replaces another in the a compound, A + BX  AX + B Double-Replacement – 2 elements switch places, precipitate forms, 2 ionic compounds produced, AX + BY  AY + BX Combustion – type of synthesis, fire, CxHy + O2  CO2 + H2O

Compare and contrast endothermic and exothermic reactions. Exothermic = releases heat to outside Endothermic = absorbs heat, add heat to the reaction

Describe the factors that affect reaction rate. Catalyst/Inhibitor Temperature – increase temp = speeds up the reaction Surface Area – break substance down into smaller parts (more surface area exposed) = speeds up the reaction Concentration – higher concentration of atoms = speeds up the reaction because more collisions Discuss the effects of catalysts and inhibitors on the speed of chemical reactions Catalyst = something added to a reaction that remains unchanged, speeds up the reaction Inhibitor = stops or slows down the reaction