Electron dot diagram Diagram showing element symbol and the number of valence electrons in a paired arrangement. You can determine the number of bonds that will be made by counting the number of unpaired electrons. coefficient Large number in front of a chemical formula that tells you how many molecules you have. 2NaOH subscript Small number to the lower right of an element in a chemical formula that tells you how many atoms of that element are in the compound. H​2​O Covalent bond bond between 2 or more non-­metals where electrons are shared Ionic bond Bond between a metal and a nonmetal. The metal gives (or transfers) its electron to the non-­metal. Atoms become charged ions. Polar covalent bond Covalent bond where electrons are shared unevenly. Example is water. The oxygen share electrons with the hydrogen but it hogs them more of the time giving the ends of the molecule slight positive and negative charges Solution Mixture that looks like one single substance. Happens between substances with the same polarity. Example: salt and water are both polar so they make a solution suspension Mixture between substances of different polarity. Substances stay separate. Example: Oil is nonpolar and water is polar. They don’t mix. polarity Polar means having charged ends of a molecule. There is a positive side and a negative side. Metallic bond Bond between two or more metals. Sea of valence electrons just flowing around the rest of the atoms. Makes metals great conductors of electricity. ion Atom that has gained or lost electrons and therefore has a positive or negative charge. mixture Combination of 2 or more substances where the substances do not change their chemical identity. element Pure substance made of only one type of atom found on the periodic table of elements Gold, carbon, oxygen compound Substance formed by the chemical bonds between two or more types of atoms. The compound has different properties than the elements that make it up. Water, carbon dioxide acid Substance that releases H+ ions in solution with water. Red in universal indicator 1-­6 on the pH scale. The stronger the acid (lower the pH) the more H+ ions there are. base Substance that releases OH-­ ions in solution. Blue/Purple in universal indicator. 8-­14 on the pH scale. H+ ion Released by acids in solution. The more there are, the stronger the acid. And the lower the pH. OH-­ ion Released by a base in solution. The more there are, the stronger the base and higher the pH level. neutral Middle of the pH scale. 7 -­ green in universal indicator. H+ and OH+ ions are equal. Water. Chemical change Change to a substance that creates a new substance. Burning wood, reacting metal and acid, metal corroding Physical change Change to a substance that doesn’t create a new substance. Tearing paper, boiling water, melting ice, dissolving salt endothermic Chemical reaction where temperature goes down and it feels colder. Energy is absorbed into compound and taken away from environment. exothermic Chemical reaction that releases heat energy and feels hotter. Temperature goes up. Law of Conservation of Mass Matter is not created or destroyed in a chemical reaction. Atoms are only rearranged. reactants Left side of the arrow in a chemical equation. What goes into the reaction products right side of the arrow in a chemical equation. What comes out of the reaction Synthesis reaction A + B → AB Decomposition reaction AB → A + B Single replacement reaction A + BC → AC + B Double replacement reaction AB + CD → AC + BD Combustion reaction HC + O​2​ → CO​2 ​+ H​2​O Controlling Chemical Reactions: Surface area The larger the surface area (powdered), the faster the reaction will go. There is more reactants exposed to each other. Controlling Chemical Reactions: temperature The higher the temperature, the faster the reaction. The higher kinetic energy means the particles of reactant move faster increasing the likelihood of collisions Controlling Chemical Reactions: concentration Increasing the concentration of a reactant (like using a stronger acid) makes the reaction go faster. This makes more reactants available and collisions more likely. Controlling Chemical Reactions: : catalyst A catalyst is like a reaction match maker. It lowers the activation energy needed to start a reaction making it go faster