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To check if a substance is an acid or an alkali (base), you can use litmus paper or a pH indicator. Litmus paper turns red in acidic solutions and blue in alkaline solutions. pH indicators, like universal indicator, provide a range of colors to indicate the strength of acidity or alkalinity on the pH scales.
Detailed Explanation:
Litmus Paper Test:
Blue litmus paper: Turns red in acidic solutions.
Red litmus paper: Turns blue in alkaline solutions.
Neutral: Neither litmus paper changes
2. pH Indicator (Universal Indicator):
A pH indicator, like universal indicator, can be used in liquid form or as strips of paper.
It changes color based on the pH of the solution.
Acidic: Solutions with a pH below 7 will turn the indicator red, orange, or yellow.
Alkaline: Solutions with a pH above 7 will turn the indicator blue or purple.
Neutral: Solutions with a pH of 7 (like pure water) will turn the indicator green.
Key Concepts:
Acids:
Substances that release hydrogen ions (H+) when dissolved in water. They have a pH below 7.
Alkalis (Bases):
Substances that release hydroxide ions (OH-) when dissolved in water. They have a pH above 7.
pH Scale:
A scale from 0 to 14 that measures the acidity or alkalinity of a solution.
0-6: Acidic.
7: Neutral.
8-14: Alkaline (Basic).