alkali

«alkali» in Mova's school dictionary: a chemical that is the opposite of an acid; it can cancel… — its meaning for a pupil, its sense in the lessons and examples, with 5 sentences of Mova's corpora that use it.

part of speech

noun (an alkali, alkalis or alkalies); adjective form: alkaline

meaning for a pupil

1) (science) An alkali is a chemical that is the opposite of an acid; it can cancel out an acid. tree →

2) (science) An alkali dissolves in water and makes a solution with a pH above 7. tree →

3) Strong alkalis, like some oven cleaners, can burn skin and eyes, just like strong acids. tree →

sense in the lessons

In school science the word comes with acids, pH, indicators and neutralisation: acid + alkali makes a salt and water. Litmus paper turns blue in an alkali, and universal indicator turns blue or purple. In everyday life alkalis are in soap, toothpaste, baking soda and indigestion tablets. Safety: cleaning products with alkalis carry warning signs; wear goggles and gloves. Phrases: «acids and alkalis», «a strong alkali», «a weak alkali», «alkaline batteries».

examples

• Soap is a mild alkali, so it feels slippery. tree →
• We tested the liquids to see which were acids and which were alkalis. tree →
• Litmus paper turns blue in an alkali. tree →
• An alkali can neutralise an acid. tree →
• Indigestion tablets contain a weak alkali that calms stomach acid. tree →
• The oven cleaner is a strong alkali, so Mum wears rubber gloves. tree →
• Toothpaste is slightly alkaline. tree →
• Bicarbonate of soda makes an alkaline solution in water. tree →

note

Plural «alkalis» (also «alkalies»); the adjective is «alkaline» (alkaline batteries, alkaline soil). Pronounced AL-ka-lie. Trap: an alkali is not «safe» just because it is not an acid; strong alkalis are dangerous too. A base is the wider word; an alkali is a base that dissolves in water. pH 7 is neutral, below 7 acid, above 7 alkali.

In the corpora

• Baking soda is a mild alkali, the opposite of an acid.
• When an acid meets an alkali, they react and cancel each other out: this is called neutralisation.
• Dad takes an antacid tablet for heartburn: the alkali in it cancels some stomach acid and the burning eases.
• Gardeners spread lime, an alkali, on sour soil for the same reason.
• Strong alkalis, like oven cleaner, can burn skin even worse than some acids, so they say "wear gloves".

Trees and pragmatics

Every meaning and example of «alkali» parsed by Mova, each sentence with its dependency tree and frames.