Year 8 Science · Unit 3 · Lesson 13

Modelling Chemical Change

Foundation Worksheet

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Date

Class

Learning Goals

Write and interpret word equations for chemical reactions.
Identify reactants and products in a word equation.
Classify a word equation by its type of chemical change (combustion, decomposition, oxidation, photosynthesis, fermentation, respiration).

Warm Up

Sort it!

For each substance below, decide whether it is a reactant, a product, or could be either depending on context. Write each substance in the correct box. Some substances may go in "Could be either."

iron iron oxide (rust) carbon dioxide oxygen water wood vinegar salt (sodium chloride) ash hydrochloric acid

Reactant (always starts a reaction)

Product (always made in a reaction)

Could be either (context-dependent)

Your Turn

Match each word equation to its type

Draw a line connecting each word equation on the left to the type of chemical change it represents on the right. Or write the matching letter next to each equation.

Word Equation	Your answer	Type of Chemical Change
iron + oxygen → iron oxide		A. Combustion (rapid reaction with oxygen that releases heat and light)
methane + oxygen → carbon dioxide + water		B. Decomposition (one substance breaks into two or more)
hydrogen peroxide → water + oxygen		C. Oxidation / rusting (metal reacts slowly with oxygen)
carbon dioxide + water → glucose + oxygen		D. Photosynthesis
glucose → carbon dioxide + ethanol		E. Fermentation
glucose + oxygen → carbon dioxide + water + energy		F. Cellular respiration

Show What You Know

1. Write the word equation for the reaction between calcium carbonate (limestone) and hydrochloric acid to produce calcium chloride, water, and carbon dioxide. Label the reactants and products.

Recall 2 marks

2. Why do scientists say that atoms are "rearranged" in a chemical reaction, rather than "created" or "destroyed"? Link your answer to the idea of conservation of mass.

Recall 2 marks

Wrap Up

In one sentence, what was the main idea of this lesson?