ACIDS AND BASES DAY 3

INTRODUCTION What do you suppose happens when you mix an acid and a base together? Hydrochloric acid and sodium hydroxide can both cause severe burns if you get them on your skin. What kind of horrible things can you imagine that might happen?

INTRODUCTION Mix them together and they cancel each other out.

INTRODUCTION The chemical reaction between these two compounds produces two new compounds with different chemical properties. The reaction between an acid and a base forms a neutral substance. When red or blue litmus paper is placed in a neutral substance they show no change of color.

INTRODUCTION When acids and bases are mixed together the reaction always creates two new substances, water and salt are always formed in a neutralization reaction. Most reactions are not %100 reactions, you usually don’t get all the acid or all the base used up in the reaction.

Na+ ions and Cl- ions combine to make NaCl, salt. H+ ions and OH- ions combine to make H2O, water. During the reaction, the ions in the acids and bases form together this way. The chlorine ions and sodium ions form to make salt, and the hydrogen ions and hydroxyl ions form together to make water.

INTRODUCTION ELECTROLYTES

INTRODUCTION Ions in a solution are called electrolytes. Electrolytes conduct electrical currents. Pure distilled water is NOT a good conductor of electricity. Pure water lacks ions which are necessary to carry the electrical current through the solution. So pure water is not an electrolytic solution.

INTRODUCTION A substance that doesn’t conduct an electrical current when dissolved in water is called a nonelectrolyte. Sugar is another type of nonelectrolyte, because it doesn’t form ions when dissolved. It creates a molecular solution. Molecular solutions don’t conduct electricity because they don’t create ions.

INTRODUCTION Electrolytes conduct electricity because they form ions that can move and carry the electrical current when dissolved in water. This example uses a current meter on the top to show how much electricity flows through the solution. The one on the left has a lot of ions so it has a higher reading. The one in the middle has a lower amount of ions so the flow is less. The one on the left has almost no ions so there is almost no current flow through that solution.

Electrolytic solution on the left conducts an electrical current Electrolytic solution on the left conducts an electrical current. Nonelectrolytic solution on the right does not conduct an electrical current.

OBJECTIVES Describe what happens when acid reacts with a base. Explain how ions in a solution conduct electricity.

IN QUESTION Create a data table that lists each of these substances as an acid, a base, or neutral substance. Lemons, distilled water, urine, apples, drain cleaner, soap, vinegar, tomatoes, toothpaste, dishwashing liquid, baking soda, ammonia, antacids, batteries

ANSWER Acids – lemon, apple, battery, tomato, urine, vinegar Neutral – distilled water Base – ammonia, soap, toothpaste, baking soda, dishwashing liquid, antacids, drain cleaner

VOCABULARY Electrolyte – Substance that conducts an electric current when dissolved in water. Neutralization – Reaction between an acid and a base which produces salt and water. Ionization – Formation of ions.

NOTES A reaction between an acid and a base results in formation of water and salt. A neutralization reaction produces a compound with different chemical properties than the reactants. Neutral compounds have a pH of 7.

NOTES Substances that form ions are electrolytes. Distilled water doesn’t conduct electricity well, it lacks particles to carry the electrical current.

NOTES Electrolytes carry a current in a solution because they provide particles that can move. Salt water is an excellent conductor of electricity. Sugar water is a poor conductor because it lacks electrolytes.

OUT QUESTION How could you identify a substance as an electrolyte or a nonelectrolyte (without tasting it)? Test it in a solution to see if it conducts electricity.