What You Need to Know

A chemical reaction occurs when substances interact to form new substances with different properties

Observable signs of a chemical reaction include: colour change, gas production (bubbling), heat or light release, and formation of a precipitate

Common examples include rusting iron, cooking food, burning, and mixing baking soda and vinegar

Unlike a physical change, a chemical change is usually irreversible — you cannot easily get back the original substances

Key Vocabulary

A process in which substances interact and change to form new substances

A starting substance that takes part in a chemical reaction

A new substance formed as a result of a chemical reaction

Cannot be easily undone or returned to the original state

Select the correct answer for each question. Click "Check Answer" to see if you are right.

Question 1

Which is the BEST evidence that a chemical reaction has occurred?

Ice melting into water A new gas bubbling up when vinegar and baking soda are mixed Salt dissolving in water A glass being broken

Question 2

Cooking an egg is a chemical change because:

The egg gets warm The egg changes colour slightly New substances form and the change cannot be reversed The egg moves from the shell to the pan

Question 3

In the reaction: baking soda + vinegar → carbon dioxide + water + sodium acetate, what are the PRODUCTS?

Baking soda and vinegar Baking soda only Vinegar only Carbon dioxide, water, and sodium acetate