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What are the five "clues" that a chemical change has occurred?

Answer 1

Change in colour, change in temperature, change in smell, formation of a precipitate, formation of gas bubbles

A chemical change can be detected by a change in color, temperature (exothermic or endothermic), smell, precipitate formation, gas bubble formation, or a change in the chemical composition of the reactants, such as the breaking and formation of chemical bonds.

The five "clues" are not absolute indicators; for example, painting a wall may change its color without changing its chemical composition. This is a physical change rather than a chemical change.

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Answer 2

Natalie Anton

The following five indicators indicate the presence of a chemical change: 1. Precipitate formation; 2. Gas evolution; 3. Color change; 4. Temperature change (heat absorbed or evolved); and 5. Light or sound production.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.