The pH scale and acid-base reactions are everywhere in your...
Chemistry229 views·Updated Jun 18, 2026·1 pageUnderstanding the pH Scale: Acids, Alkalis, and Neutralization
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Orsini Doko@orsinidoko_hejl
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pH Scale and Indicators
Ever wondered why lemon juice tastes sour whilst soap feels slippery? It's all about the pH scale, which measures how acidic or alkaline something is on a scale from 0 to 14.
Acids contain lots of H+ ions and turn universal indicator red, yellow, or orange. Think vinegar, citrus fruits, and your stomach acid. Neutral substances like pure water sit right in the middle at pH 7 - they're neither acidic nor alkaline.
Alkalis are packed with OH- ions and turn universal indicator green, blue, or purple. Common examples include soap, bleach, and antacid tablets. The further you move from pH 7, the stronger the acid or alkali becomes.
Different indicators help us identify acids and alkalis through colour changes. Universal indicator gives you the full rainbow of colours, whilst litmus paper simply turns red in acid and blue in alkali. Phenolphthalein stays colourless in acid but turns bright pink in alkali - perfect for spotting the exact moment when neutralisation happens!
Quick Tip: Remember "Red = Acid" for litmus paper, and acids always have pH values below 7.
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Chemistry229 views·Updated Jun 18, 2026·1 pageUnderstanding the pH Scale: Acids, Alkalis, and Neutralization
O
Orsini Doko@orsinidoko_hejl
The pH scale and acid-base reactions are everywhere in your daily life - from the fizzy drinks you love to the soap you wash with. Understanding how acids and alkalis behave will help you make sense of countless chemical reactions...
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of 1
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pH Scale and Indicators
Ever wondered why lemon juice tastes sour whilst soap feels slippery? It's all about the pH scale, which measures how acidic or alkaline something is on a scale from 0 to 14.
Acids contain lots of H+ ions and turn universal indicator red, yellow, or orange. Think vinegar, citrus fruits, and your stomach acid. Neutral substances like pure water sit right in the middle at pH 7 - they're neither acidic nor alkaline.
Alkalis are packed with OH- ions and turn universal indicator green, blue, or purple. Common examples include soap, bleach, and antacid tablets. The further you move from pH 7, the stronger the acid or alkali becomes.
Different indicators help us identify acids and alkalis through colour changes. Universal indicator gives you the full rainbow of colours, whilst litmus paper simply turns red in acid and blue in alkali. Phenolphthalein stays colourless in acid but turns bright pink in alkali - perfect for spotting the exact moment when neutralisation happens!
Quick Tip: Remember "Red = Acid" for litmus paper, and acids always have pH values below 7.
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What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
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Explore key AQA GCSE Chemistry practicals, including flame tests, titration, and gas identification. This resource covers essential techniques for analyzing ions, making salts, and understanding reaction kinetics. Perfect for students preparing for exams and practical assessments.
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