"Preliminary Understanding of Acids and Bases" Acids and Bases PPT Courseware 2

Description

"Preliminary Understanding of Acids and Bases" Acids and Bases PPT Courseware 2

Knowledge review

Knowledge point 1 Acid-base indicator

[Note] ①When the indicator encounters an acidic solution or an alkaline solution, it is the indicator that changes color, not the acidic solution or alkaline solution.

②According to the color change of the indicator, the acidity and alkalinity of the solution can be judged, but it cannot be determined that the solution must be acid or alkaline. Because some salt solutions may be acidic or alkaline, such as Na2CO3 solution, which may be alkaline.

Knowledge point 2 The composition of acids and bases

Acid is made up of _______ and _______.

Bases are composed of ______________ and ______________.

Knowledge point 3: The concept and measurement method of solution pH

The acidity and alkalinity of a solution can be expressed by pH. The relationship between pH and the acidity and alkalinity of the solution is as shown in the figure:

pH<7: The solution is ____, the ___ the pH is, the stronger the acidity;

pH=7: The solution shows ___ property;

pH>7: The solution is ___. The higher the pH, the stronger the alkalinity.

pH measurement method: Place a small piece of pH test paper on ______, dip the _______ into the liquid to be measured, drop it on the test paper, and compare the color of the test paper with __________.

Example analysis

►Type 1 Acid-base indicator

Propositional perspective: The color change of an acid-base indicator when it encounters an acid-base solution.

Example 1: After learning about acid-base indicators, classmate Xiaohong tried to make her own indicator using purple cabbage. She put the chopped purple cabbage into a glass, added _____ to soak it, and filtered the soaked juice with gauze to get a homemade indicator. This indicator turns blue when exposed to lime water and red when exposed to hydrochloric acid. Put a small amount of white vinegar into a glass and add a few drops of homemade instructions

agent, showing ____ color.

[Method Instructions] In addition to the commonly used litmus and phenolphthalein solutions, acid-base indicators can also be replaced by plant juices.

[Analysis] Pigments are generally not easily soluble in water but easily soluble in alcohol, so alcohol should be added for soaking. The homemade acid-base indicator made with purple cabbage turns blue when exposed to lime water and red when exposed to hydrochloric acid. Both white vinegar and hydrochloric acid are acidic, so add a few drops of the homemade indicator to the white vinegar and the indicator should appear red.

►Type 2 pH and acidity and alkalinity

Propositional perspective: Determine the acidity and alkalinity of a substance based on its pH.

Example 2 A classmate measured the pH of some food and daily necessities at home. The results are as follows:

The following statement is correct ()

A. Vinegar can remove the astringency of preserved eggs

B． Toothpaste is a neutral substance

C. Soy sauce is alkaline and can turn phenolphthalein red

D． People with excessive stomach acid should eat more grapes

[Analysis] To answer this question correctly, you must understand the relationship between the pH and acidity and alkalinity of the solution. The pH of vinegar is 3, which is an acidic solution. The pH of preserved eggs is 10, which is alkaline. Neutralizing the acid and alkali can remove the astringent taste, so option A is correct. The pH of toothpaste is 9, which is an alkaline substance, so option B is wrong. The pH of soy sauce is 5, which is an acidic substance. It cannot change the color of phenolphthalein, so option C is wrong. The pH of grapes is 4, which is an acidic substance. People with excessive stomach acid should not eat more, so option D is wrong.

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"Preliminary Understanding of Acids and Bases" Acids and Bases PPT courseware:

"Preliminary Understanding of Acids and Bases" Acids and Bases PPT Courseware Thinking As far as you know, what substance can make purple litmus red? What are the uses of purple litmus reagent? 1. Acid-base indicator 1. Purple litmus reagent: Acidic substances make the purple litmus reagent turn red; alkaline...

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Update Time: 2024-09-08

This template belongs to Chemistry courseware Beijing Curriculum Reform Edition Ninth Grade Chemistry Volume 2 industry PPT template

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