In the seventeenth century, the Irish writer and chemist Robert Boyle first labeled substances as either acids or bases.
What is an acid? An acid is a solution that has an excess of H+ ions. It comes from the Latin word acidus that means "sharp" or "sour". Below 7 on pH scale The more H + ions, the more acidic the solution. Ion- Atom with a positive or negative charge.
Uses of Acids Acetic Acid = Vinegar Citric Acid = lemons, limes, & oranges. It is in many sour candies such as lemonhead & sour patch. Ascorbic acid = Vitamin C which your body needs to function. Sulfuric acid is used in the production of fertilizers, steel, paints, and plastics. Car batteries
What is a base? A base is a solution that has an excess of OH- ions. Another word for base is alkali. Bases are substances that can accept hydrogen ions
Uses of Bases Bases give soaps, ammonia, and many other cleaning products some of their useful properties. The OH- ions interact strongly with certain substances, such as dirt and grease. Chalk and oven cleaner are examples of familiar products that contain bases. Your blood is a basic solution.
Properties of an Acid Tastes Sour Conduct Electricity Corrosive, which means they break down certain substances. Many acids can corrode fabric, skin, and paper Some acids react strongly with metals Turns blue litmus paper red Picture from BBC Revision Bites http://www.bbc.co.uk/schools/ks3bitesize/science/chemistry/acids_b ases_1.shtml http://www.bbc.co.uk/schools/ks3bitesize/science/chemistry/acids_b ases_1.shtml
Properties of a Base Feel Slippery Taste Bitter Corrosive Can conduct electricity. (Think alkaline batteries.) Do not react with metals. Turns red litmus paper blue.
Question? A soda has a pH of 3.5 ------ acid or base? A substance is really slippery…. Acid or base? OH- is a hydroxide ion or hydronium ion? H 3 O + and H+ is a hydroxide ion or a Hydronium ion?
pH Scale pH is a measure of how acidic or basic a solution is. pH means Power of Hydrogen The pH scale ranges from 0 to 14. Acidic solutions- pH values below 7; more hydronium ions = lower pH; ***acids react with water, and release H+ or H3O+ ions. A solution with a pH of 0 is very acidic. A solution with a pH of 7 is neutral. Pure water has a pH of 7. Basic solutions have pH values above 7. ***bases react with water and produce hydroxide ions --more OH ions = alkaline (basic)
pH scale liquid drain cleaner 14 tomato juice 4.1 eggs 8 grapefruit juice 3 distilled water 7 milk of magnesium 10.5 toothpaste 9.9 hydrochloric acid 1 milk 6.6 battery acid 0 black coffee 5 soapy water 12 lemon juice 2.3 bleach 13 over cleaner 13 ammonia 11.9 0-678-14 Strong acidsStrong bases
Acid – Base Reactions A reaction between an acid and a base is called neutralization. An acid-base mixture is not as acidic or basic as the individual starting solutions.
How does a salt form? When an acid and a base react, a salt and water are formed ( products). HCl + NaOH NaCl + HOH(water) Acid + base salt + water Acids tend to have H in front of formula Bases tend to have an OH in formula
Acid – Base reactions Each salt listed in this table can be formed by the reaction between an acid and a base. examples
Why Learn about Acids & Bases? What do you think is the pH level of FairLawn tap water? The pH of a swimming pool must be checked periodically. Why? Is it important for Lakes & Rivers to maintain a certain pH?
Today’s Experiment Test the pH of a variety of substances in 6 stations.
You will have litmus paper and pH test paper, and pH meters. These are indicators of pH or whether a substance is an acid or a base. Litmus paper--(purple ): determines acid or base (red or blue) pH paper --( yellow) gives you a value on the pH scale from 0-14 pH scale from 0-14 pH meter: measures pH accurately