Question

name: madison clarke
period: 4
date: oct 7
grade:11
do now — chemical combining of substances (time: 5 - 7 minutes)
learning goal: i can identify when a chemical change happens.

1. a piece of magnesium is dropped into acid. bubbles form.

→ is this a physical or chemical change? why?

1. two clear liquids are mixed and a yellow solid appears.

→ what is the solid called? what evidence shows a chemical reaction happened?

1. balance this equation:

fe + o₂ → fe₂o₃

Explanation:

Step1: Identify change type for magnesium - acid reaction

A chemical change occurs when new substances are formed. When magnesium is dropped into acid and bubbles form, a gas (hydrogen) is produced. This is a chemical change because a new substance is created.

Step2: Identify solid and evidence for liquid - liquid reaction

The solid formed when two liquids react is called a precipitate. The formation of a new substance (the yellow solid) is evidence of a chemical reaction.

Step3: Balance the chemical equation

We need to balance the number of atoms on both sides of the equation. For the equation $Fe + O_2
ightarrow Fe_2O_3$, we multiply $Fe$ by 4, $O_2$ by 3 and $Fe_2O_3$ by 2 to get $4Fe + 3O_2
ightarrow 2Fe_2O_3$.

Answer:

1. Chemical change. New substance (gas) formed.
2. The solid is called a precipitate. Formation of a new substance is evidence.
3. $4Fe + 3O_2

ightarrow 2Fe_2O_3$