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Acids and Bases Sour and Bitter Acids: The term acid, in fact, comes from the Latin term acere, which means sour. Acids taste sour, are corrosive to.

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Presentation on theme: "Acids and Bases Sour and Bitter Acids: The term acid, in fact, comes from the Latin term acere, which means sour. Acids taste sour, are corrosive to."— Presentation transcript:


2 Acids and Bases Sour and Bitter

3 Acids: The term acid, in fact, comes from the Latin term acere, which means sour. Acids taste sour, are corrosive to metals, change litmus (a dye extracted from lichens) red, and become less acidic when mixed with bases. Bases: Bases (also known as alkalies) feel slippery, change litmus blue, and become less basic when mixed with acids. Acids and Bases Neutralization: (Acid) + (Base) = (Salt) + (Water) HCl + NaOH = NaCl + H 2 O

4 Definitions of Acids and Bases  An acid is a substance that breaks into H+ ions in an aqueous solution.  A Base (alkaline) is a substance that breaks into OH − ions in an aqueous solution.  Note: aqueous solution is any solution where H 2 O is the solvent.

5 Characteristics Of Acids Acids can be characterized by: 1. A sour taste. 2. It turns blue litmus paper red 3. It tastes sour. Try drinking lemon juice (citric acid)

6 Characteristics of Bases A Base is characterized by: 1. A bitter taste. (Milk of Magnesia) 2. It feels slippery. (Soapy Water) 3. It turns Red Litmus Blue.

7 Where in the….S What part of the tongue can taste a lemon or other sour things?

8 Answer The green areas are where you would taste sour foods such as a lemon.

9 Where in the….B Where might you taste something bitter like baking soda?

10 Answer The green area is where you would taste bitter foods such as baking soda. This tells you how not to take those bitter pills.

11 Acid rain is rain that has been made acidic by certain pollutants in the air.acidic Acid rain is a type of acid deposition, which can appear in many forms.acid deposition Wet deposition is rain, sleet, snow, or fog that has become more acidic than normal. Dry deposition is another form of acid deposition, and this is when gases and dust particles become acidic. Both wet and dry deposition can be carried by the wind, sometimes for very long distances. Acid deposition in wet and dry forms falls on buildings, cars, and trees and can make lakes acidic. Acid deposition in dry form can be inhaled by people and can cause health problems in some people. Acid Rain Lifted from EPA website

12 What is the pH scale?  The pH scale measures how acidic or basic a solution is.  It ranges from  7 is neutral.  A pH less than 7 is acidic. Lower pH, stronger Acid.  A pH of greater than 7 is basic. Higher pH, stronger base  pH stands for the “power of Hydrogen”

13 Lemon Juice4 Baking Soda8 Aspirin5 Ammonia10 Milk of Magnesia8 Lava Soap10 Borax9 Water7 Lemon Soap6 Vinegar4 Tonic Water4 Liquid Plumber12 Acid or Base? Weak or Strong?

14 [H + ]pHExample Acids 1 x HCl - Hydrochloric acid 1 x Stomach acid 1 x Lemon juice 1 x Vinegar 1 x Soda 1 x Rainwater 1 x Milk Neutral1 x Pure water Bases 1 x Egg whites 1 x Baking Soda 1 x Tums ® antacid 1 x Ammonia 1 x Mineral Lime - Ca(OH) 2 1 x Drano ® 1 x NaOH pH-Table

15 Indicators Indicators-- An indicator is a special type of compound that changes color as the pH of a solution changes, thus Gives us an approximate pH of the solution. Many dyes (chemicals) are sensitive to hydrogen-ion concentration. Beyond a certain threshold, they change visible color and are used as indicators of the relative pH of a solution. Litmus paper - Paper with powder extracted from certain plants that tests the pH of a substance. Acid turns red whilepHAcid basebase turns blue; neutral remains white.

16 Phenolphthalein  Phenolphthalein is a sensitive pH indicator with the formula C 20 H 14 O 4. Often used in titrations, it turns from colorless in acidic solutions to pink in basic solutions, the color change occurring between pH 8 and pH 10. If the concentration of indicator is particularly strong, it can appear purple. 

17  Phenolphthalein is insoluble in water, and is usually dissolved in alcohol for use in experiments.  It is a colorless, weak acid, which can lose H+ ions in solution. However, the phenolphthalein ion is pink. When a base is added to the phenolphthalein, the [atom  ion] equilibrium shifts to the ionization because H+ ions are removed.

18 Make your own "litmus paper" 1. Chop the red cabbage up with a sharp knife. 2. Crush it with a "pestle and mortar" OR put it in a food mixer and grind it. 3.Add a very small amount of water. 4.Decant the blue liquid (pour the liquid into a clean glass). 5.Soak some blotting paper in the blue liquid. 6.Let the blotting paper dry out. 7.Cut the blue papers into small squares. When you buy the red cabbage it is actually blue. It will be quite blue when you slice it up and add some tap water. That is because your tap water is very slightly alkaline. If you add some vinegar it will turn red. This is because there is a pigment (coloured chemical) in the red cabbage which acts as a pH indicator.

19 Why is acid an acid? All substances are made up of millions of tiny atoms. These atoms form small groups called molecules. In water, for example, each molecule is made up of two hydrogen atoms and one oxygen atom. The formula for a molecule of water is H 2 O. "H" means hydrogen, "2" means 2 hydrogen atoms, and the "O" means oxygen.

20 Why continued When an acid is poured into water, it gives up H (hydrogen) to the water. When a base is poured into water, it gives up OH (hydroxide) to the water. Stronger acids give up more protons (the positively charged parts of atoms); stronger bases give up more OH- (hydroxide). Neutral substances have an even balance of protons and OH-.

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