CELL COMPOUNDS Water Acids, Bases & Buffers Water Acids, Bases & Buffers.
Acids and Bases Chapter 3 Sections 2 + 3 Pages 62-71.
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Transcript of Acids and Bases Chapter 3 Sections 2 + 3 Pages 62-71.
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Acids and Bases
Chapter 3 Sections 2 + 3Pages 62-71
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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.
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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
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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
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Acids React with Metals
• Acids react with some metals to produce Hydrogen gas.
• Acids need reactive metals to produce the gas.
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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
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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
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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.
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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.
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Uses of Bases
• Sodium hydroxide: makes soap and paper
• Calcium hydroxide: cement and plaster
• Ammonia: cleaner and fertilizer
• Magnesium hydroxide and aluminum hydroxide: antacids
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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.
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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.
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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.
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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: acid7: neutralGreater than 7: base
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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.
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pH and the Environment
• Rain pH (5.5-6)• Soil pH, some plants
grow better in either acidic or basic soil.
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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)
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More info on Acids and Bases
• http://www.chem4kids.com/files/react_acidbase.html