化学双语教学 溶液的酸碱度ph.ppt

What is pH? Sour!(酸) Some of our favorite foods make our tongue curl up because they are Sour. Bitter!（苦） Some foods have a “bite” of their own because they’re somewhat bitter. WHY? Acids and Bases Acid and Bases Acid and Bases Acid and Bases Acidic/Basic There is a scientific reason for this: These foods are either acidic or basic. Other substances besides foods have these characteristics. Acids Examples: Lemon juice Soda Vinegar Car battery acid (dangerous!) General properties of acids Taste sour Strong acids can burn skin eyes Turn litmus Turn phenolphthalein React with active metals – Fe, Zn… React with bases Bases Examples: Coffee Baking soda Soap Drain cleaner (dangerous!) General properties of bases No I am Not: Some things are not an acid or a base --- are neutral(中性) For example pure water Indicator(指示剂) What is pH? pH pH is a measurement of the acidic degree and the basic degree of the sample How Do We Measure pH? We measure pH by using special strips of paper called pH paper The pH Scale pH scale ranges from 0 -14 pH = 7 is neutral; neither acid nor base Pure water is pH 7 Low pH → acid High pH → base How Does It Work? The paper is treated with chemicals that change color to show the pH. When the paper touches the substance being tested, it turns a specific color to tell if the substance is an acid or a base. The pH Scale Why is pH important? Summary Chemicals may be classed as acids or bases (酸与碱). Substances that are neither acids nor bases are neutral（中性的）. pH measures how acidic or basic a solution is. Learning Check 1 Describe the solution in each of the following as: 1) acid 2) base or 3)neutral. A. ___soda B. ___soap C. ___coffee D. ___ wine E. ___ water F. ___ grapefruit G. ___ milk Learning Check 1 Identify each as properties of an A) acid or B) base ____ 1. Sour