Acids, Bases & Salts
Science, Grade 7
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Strength of Acids & Bases Characteristics of Acids Characteristics of Bases litmus paper • have a sour taste • react with metals • turn blue litmus paper red • conduct electric current • have a bitter taste • feel slippery • change red litmus paper to blue Acids react with most metals producing hydrogen gas. Acids turn blue litmus paper red. Hydrogen ions and chloride form when hydrochloric acid (HCl) is dissolved in water. Hydrogen ion (H+) litmus paper react with indicators 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Most Basic Most Acidic 0 Neutralization base acid neutral solution pH = 11 pH = 2 pH = 8 water water O H H bitter taste slippery feel Hydroxide ion (OH–) Acids and bases vary in strength depending on the number of molecules that break apart to produce ions when dissolved in water. The more hydrogen ions (H+) formed, the stronger the acid. Likewise, the more hydroxide ions (OH-) formed the stronger the base. The pH Scale Scientists use a pH scale to measure the strength of acids and bases. The pH scale ranges from 0 to 14. Substances with pH of less than 7 are considered acids; the lower the pH, the stronger the acid. The pH of bases ranges from 7-14 – the higher the pH the stronger the base. Neutral solutions have a pH of exactly 7. HCl NaOH Ammonia universal indicator paper sour taste Acids & Their Pr operties An acid is a type of sour substance. When placed in water, acids release hydrogen (H+) ions and negative ions. Ions are negatively or positively charged atoms. When an acidic substance dissolves in water – hydrogen atoms break away from the acid molecules. This process forms hydrogen ions. Bases & Their Pr operties A base is a type of bitter substance. When placed in water, bases release hydroxide (OH-) ions into the water. Examples of a base include soap and baking soda. Salts Acid-Base Reactions A neutralization reaction occurs when an acid and a base react to form water and a salt. The hydrogen ions (H+) from an acid react with the hydroxide ions (OH-) from a base to form water. Indicators are substances that change color when they are added to acidic solutions or alkaline (basic) solutions. The positive ions and hydroxide ions separate when sodium hydroxide (NaOH) is dissolved in water. © Copyright NewPath Learning. All Rights Reserved. 94-4806 www.newpathlearning.com Acids, Bases & Salts
Strength of Acids and Bases Characteristics of Acids \|xiBAHBDy01798rzu • _________________________________________ • _________________________________________ • _________________________________________ • _________________________________________ Bases & Their Pr operties What is a base? _____________________________ __________________________________________ __________________________________________ __________________________________________ Characteristics of Bases: • ____________________________________ • ____________________________________ • ____________________________________ Salts Acid-Base Reactions A _______________________ reaction occurs when an acid and a base react to form _______________________ and a _______________________ . Acids react with most ______________ producing hydrogen gas. The _______________________ _______________________ and _______________________ _______________________ separate when sodium hydroxide (NaOH) is dissolved in water. HCl + NaOH ➞ H 20 + Na+ + Cl- reactants products 1 2 3 4 5 6 7 8 9 10 11 12 13 14 0 Neutralization pH = 11 pH = 2 pH = 8 HCl ➞ H+ + Cl- water NaOH ➞ Na+ + OH- water Describe the strength of acids and bases: _______________________ _______________________ _______________________ _______________________ _______________________ _______________________ _______________________ _______________________ The pH Scale How is the pH scale used? _______________________ _______________________ _______________________ _______________________ _______________________ _______________________ HCl NaOH Ammonia universal indicator paper Key Vocabulary Terms • acid • base • hydrogen ion • hydroxide ion • indicator • litmus paper • neutral solution • pH scale • salt The hydrogen ions ( H+) from an acid react with the hydroxide ions ( OH-) from a base to form __________________________. Most Basic Most Acidic _______________________ _______________________ and _______________________ form when hydrochloric acid (HCl) is dissolved in water. Acids & Their Pr operties What is an acid? _____________________________ ___________________________________________ ___________________________________________ ___________________________________________ ___________________________________________ What is an indicator? ________________________ ________________________ ________________________ ________________________ _________________ © Copyright NewPath Learning. All Rights Reserved. 94-4806 www.newpathlearning.com Acids, Bases & Salts
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