Year 8 Science · Unit 2 · Lesson 1
Apply Worksheet
Learning Goals
Order the steps
Number the events from 1 to 6 to show the correct order, starting from the smallest level of matter. Event 1 = what comes first.
| Order | Event |
|---|---|
| Substances can be physically mixed together without any chemical bonding occurring. | |
| Atoms of different types bond together chemically in fixed proportions, forming a new substance with different properties. | |
| An element is formed, a pure substance containing only one type of atom. | |
| Individual atoms of a particular type exist as the fundamental building block. | |
| A mixture or pure substance results, depending on whether bonding occurred. | |
| Atoms of one type group together, all identical, making up a sample of a pure element. |
Real-world context
Salt water from the ocean covers over 70% of Earth's surface. Seawater contains water (H₂O), dissolved salt (NaCl), and small amounts of other minerals such as magnesium sulfate. Each component, water and salt, is itself made of atoms that are chemically bonded, but the components are not bonded to each other.
(a) Using lesson vocabulary, classify seawater. Is it an element, a compound, or a mixture? Explain your reasoning.
(b) If you evaporate the water from seawater, solid salt crystals are left behind. What does this tell you about how the water and salt are combined in seawater?
1. Oxygen gas (O₂) and iron (Fe) are separate elements. When they react, they form iron oxide (rust). Using particle-level ideas, explain what changes when the elements become a compound.
2. A student says: "Salt (NaCl) is a mixture because it contains sodium AND chlorine." Is the student correct? Explain why or why not.
Wrap Up
In one sentence, what was the main idea of this lesson?