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Acids and Bases

Acids and Bases. Chapter 3 Sections 2 + 3 Pages 62-71. Acids and their Properties. An acid is any compound that increases the number the of hydronium ions, H₃O⁺, when dissolved in water.

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Acids and Bases

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  1. Acids and Bases Chapter 3 Sections 2 + 3 Pages 62-71

  2. Acids and their Properties • An acid is any compound that increases the number the of hydronium ions, H₃O⁺, when dissolved in water. • Hydronium ions form when a hydrogen ion, H⁺, separates from the acid and bonds with a water molecule, H₂O.

  3. Acids have a Sour Flavor • Sour taste result of citric acid • Most acids are corrosive (can destroy body tissue, clothing, etc.) • Most acids are poisonous

  4. Acids Change Colors in Indicators • A substance that changes color in the presence of an acid or base is an indicator. • An indicator is a compound that can reversibly change color depending on conditions such as pH • Litmus paper strip usually blue and changes to red when an acid is added

  5. Acids React with Metals • Acids react with some metals to produce Hydrogen gas. • Acids need reactive metals to produce the gas.

  6. Acids Conduct Electric Current • When acids are dissolved in water, they break apart and form ions in solution. • Ions make the solution able to conduct an electric current. • Car battery-sulfuric acid

  7. Uses of Acids • Sulfuric Acid: paper, paint, detergents, fertilizer • Nitric Acid: fertilizer, rubber, plastics • Hydrochloric Acid: make metal from ore separation, clean pools, in our stomach • Hydrofluoric acid: etch glass • Citric Acid and ascorbic acid (Vitamin C): juice • Carbonic acid and phosphoric acid: soda

  8. Bases and their Properties • A base is any compound that increases the number of hydroxide ions, OH⁻, when dissolved in water. • Hydroxide ions give bases their properties: soaps, bleach/detergents, baking soda. • Properties include a bitter taste and slippery feel.

  9. Bases and their Properties • Bases change color in indicators. Changes red litmus paper to blue. • Bases conduct an electric current because bases increase the number of hydroxide ions, OH⁻, in a solution. • A hydroxide ion is a hydrogen atom and an oxygen atom bonded together. The extra electron gives the hydroxide ion a negative charge.

  10. Uses of Bases • Sodium hydroxide: makes soap and paper • Calcium hydroxide: cement and plaster • Ammonia: cleaner and fertilizer • Magnesium hydroxide and aluminum hydroxide: antacids

  11. Strengthens of Acids and Bases • Strength is not the same as concentration. • Concentration is the amount dissolved in water. • Strength depends on the number of molecules that break apart when dissolved in water.

  12. Strong Versus Weak Acids and Bases • In a strong acid or base, all of the molecules of the acid or base break apart when the acid or base is dissolved in water. • In a weak acid or base, only a few of the acid or base molecules break part when the acid or base is dissolved in water.

  13. Acids, Bases and Neutralization • The reaction between acids and bases is a neutralization reaction. (example- antacid meets stomach acid) • The hydrogen ions H⁺ (from the acid) react with the hydroxide ions OH⁻ forming H₂O, water which is neutral. If the water evaporates then ions form compounds called salts.

  14. The pH Scale • An indicator, such as litmus, can identify whether a solution contains an acid or base. • A pH is a value that is used to express the acidity or basically (alkalinity) of a system. Less than 7: acid 7: neutral Greater than 7: base

  15. Using Indictors to Determine pH • Indicators turn different colors at different pH levels. • The color of the pH strip can be compared with colors on the indicator scale to determine the pH of the solution being tested.

  16. pH and the Environment • Rain pH (5.5-6) • Soil pH, some plants grow better in either acidic or basic soil.

  17. Salts and its Uses • A salt is an ionic compound that forms when a metal atom replaces the hydrogen of an acid. • Sodium Chloride • Sodium Hydroxide (lye and baking soda) • Sodium nitrate (food preservative)

  18. More info on Acids and Bases • http://www.chem4kids.com/files/react_acidbase.html

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