Acids and Bases Science 10

Examples of Acids Lemons Stomach acid Acid rain Battery acid Vinegar

Characteristics of Acids Sour taste Can burn the skin Conducts electricity Neutralizes a base Can dissolve in water

Examples of Bases Bleach Baking soda Soap Windex Tonic water

Characteristics of Bases Bitter taste Slippery texture Can burn skin Conducts electricity Neutralizes acids Can dissolve in water

Acids, Bases, Ions and Indicators In 1884, Svante Arrhenius, a Swedish chemist defined an acid and base.

HCl (aq)  H+(aq) + Cl- (aq) Acid In an aqueous solution, acids produce hydrogen H+ ions Example: hydrochloric acid, HCl, which is found in our stomachs. In water the acid will produce H+ and Cl- ions. HCl (aq)  H+(aq) + Cl- (aq)

NaOH(aq)  OH- (aq) + Na+(aq) Bases In an aqueous solution a base produces hydroxide OH- ions Example: sodium hydroxide (NaOH). In water this base produces Na+ and OH- ions. NaOH(aq)  OH- (aq) + Na+(aq)

Acid or Base? H2CO3 (aq) → H+ (aq) + CO32- (aq) acid Ca(OH)2 (aq) → Ca2+ (aq) + OH- (aq) base

Most acids and bases are clear and colorless Most acids and bases are clear and colorless. You need an indicator to tell them apart. Indicator: a chemical that changes color as the concentration of H+ or OH- changes. There are many different indicators such as Litmus, phenolphthalein and even cabbage juice!

Litmus Test Red and blue litmus paper Acids turn blue litmus paper red. Bases turn red litmus paper blue Neutral substances will not change the colour of red OR blue litmus paper.

Other Indicators Phenolphthalein Cabbage Juice Turns bright pink in bases, at pH of 8.2 or higher Will be clear in acids Cabbage Juice A homemade indicator Turns a rainbow of colors based on various pH levels

To do: Read Pages 156-158 Notes – Acids and Bases Questions: p. 161, #’s 11, 12, 15 p. 173, #’s 4, 5

pH scale pH: the measure of the acidity of a solution. The scale ranges from 0 to 14. pH  7 = acid (less then 7) pH  7 = base (more then 7) pH 7 = neutral

Acid, Base or Neutral? H2O ↔ H+ (aq) + OH- (aq) Neutral

Please note that the aforementioned indicators (litmus and Phenolphthalein do not give an exact pH, they only tell you if your solution is an acid or a base)

pH Paper You compare the colour with a given chart Instead of telling you whether something is an acid or a base it gives you the exact pH. Source: http://escalade.nbed.nb.ca/images/ex15.jpg

pH meter

Acid or Base? milk (6.6) Baking Soda (8.7) Pure water (7.0) Acid (H+ > OH-) Baking Soda (8.7) Base (H+ < OH-) Pure water (7.0) neutral (H+ = OH-)

To Do: Read pages 159-160 Notes – pH scale Questions: p. 161, #’s 13, 16 p. 173 #’s 9, 11

Neutralization Reactions An acid and a base react together to form a new compound (a salt) and water. It’s a double replacement reaction! The general equation is: Acid + Base → Salt + Water Example: HCl + NaOH → NaCl + H2O

So the pH of the new products is close to 7 (neutral). Examples of neutralization Antacids Calcium carbonate is added to acidic lakes.

Practice Video – Acids and Bases Notes Practice Sheet