Acids, Alkalis & the pH Scale

The pH scale is your best mate for figuring out whether something is acidic or alkaline. Think of it like a number line from 0 to 14 - anything below 7 is an acid, anything above 7 is an alkali, and 7 is perfectly neutral (like pure water).

Acids are substances with a pH below 7, and they're the chemical opposite of alkalis. Common examples include lemon juice, vinegar, and hydrochloric acid. They often taste sour and can be quite reactive.

Alkalis have a pH above 7 and are the chemical opposite of acids. Soap, baking soda, and sodium hydroxide are all alkaline substances. They often feel slippery to touch and can neutralise acids.

Indicators are special chemicals that change colour to show whether something is acidic or alkaline. The universal indicator works with the full pH scale, showing different colours for different pH levels. You can also use litmus paper - blue turns red in acids, whilst red turns pink/blue in alkalis. Even red cabbage works as a natural indicator, turning red in acids, blue in neutral water, and green in alkalis like sodium hydroxide!

Quick Tip: Remember that when acids and metals react together, they create compounds called salts - completely different from table salt!