Acids, Bases, and Indicators in Grade 7 Natural Sciences
This presentation covers the topic of acids, bases, and neutrals in Grade 7 Natural Sciences. It explains the use of acid-base indicators, such as litmus paper, and how they react to different substances. The content also discusses how certain detergents and soaps act as bases and how the soil pH affects the color of flowers like the Hydrangea macrophylla.
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Presentation Transcript
Natural Sciences Grade 7 Term 2: Matter and Materials Acids, bases and neutrals (PPT 3)
Topic 3 Acids, bases and neutrals Acid-base indicators Natural Sciences - Grade 7
Using Using acid acid- -base indicators [1] base indicators [1] Indicators are substances used in laboratories to test if a substance is a base or an acid. Dyes in the indicators change colour as soon as it mixes with bases or acids. Testing a substance: Must be in liquid form. Solid substance must first be dissolved in water to make a solution. Use red and blue litmus for testing. Use a new piece of litmus paper for each test Natural Sciences - Grade 7
Using Using acid acid- -base base indicators [2] indicators [2] How litmus paper reacts to acids, bases and neutrals: Acid: Blue litmus paper Red litmus paper turns red stays red Base: Blue litmus paper Red litmus paper - - stays blue turns blue Neutral: Blue litmus paper Red litmus paper - - stays blue stays red Natural Sciences - Grade 7
Using acid Using acid- -base base indicators [3] indicators [3] An acid-base indicator is a weak acid. Most detergents and soaps turn red litmus blue, indicating that they are bases. Certain detergents and soaps may test as acids or neutrals (e.g. lemon juice added to some dishwashing liquids; citrus fruit extracts added to some shampoos; etc.). Natural Sciences - Grade 7
Using acid Using acid- -base base indicators indicators The flowers of the Hydrangea macrophylla (Christmas flower) changes colour, depending on the soil pH value. Natural Sciences - Grade 7
