Chemical Reactions - Lesson 2 (Year 9 Chemistry)

A set of Question-and-Answer flashcards covering the concepts of physical vs. chemical changes, reactants/products, chemical equations, and examples from the lesson notes.

What is the definition of a chemical reaction?

The rearrangement of atoms to transform existing substances into new substances.

What are reactants?

The substances that react with each other.

What are products?

The new substances formed by a reaction.

How can you tell a chemical reaction is occurring?

Signs include formation of a new gas, color change, temperature change, disappearance of a solid, formation of a new solid, or emission of light/sound.

What is a physical change?

A change of physical properties with no new substances formed.

What is a chemical change?

A process where new substances form.

Give an example of a physical change from the notes.

Candle wax melts.

Give an example of a chemical change from the notes.

Candle wax burns.

List typical signs of a chemical change.

Formation of a new gas, colour change, formation or disappearance of a solid, temperature change.

In a chemical equation, what goes on the left side?

Reactants.

In a chemical equation, what goes on the right side?

Products.

What does an arrow represent in a chemical equation?

The reaction; it shows the direction of the process.

How are different reactants or products separated in a chemical equation?

By plus signs.

How should a chemical equation be written in terms of layout?

Keep the equation on a single line; write reactants on the left, products on the right.

What is the difference between symbol and word equations?

They have the same structure; symbol equations show the substances with chemical symbols and indicate the elements and their relative amounts.

What does H2O tell us about the composition of water?

There are two hydrogen atoms for every oxygen atom in water.

What should be written above the arrow in a chemical equation?

Any reaction conditions required for the reaction to happen.

In the example Mg + O2 → MgO, what are the reactants and what is the product?

Reactants: magnesium and oxygen; Product: magnesium oxide.

What happens to bonds during a chemical reaction?

Old bonds break and new bonds form to produce the products.

Are dissolving coffee and crushing a can typically physical or chemical changes?

Dissolving coffee and crushing a can are typically physical changes.