Year 8 Science · Unit 2 · Lesson 05
Foundation Worksheet
Learning Goals
Fill the gap
Choose the correct word from the word bank. Each word is used once at most. Two words will not be used.
All matter is made of tiny that are far too small to see. A pure substance that contains only one type of atom is an . When atoms of different elements are chemically bonded in a fixed ratio, the result is a . If substances are only physically combined, with no bonding between them, we have a . Scientists write a , such as Fe or O, as a short, universal name for each element. A diagram shows how the particles in a sample are arranged. A simplified picture that helps us reason about something we cannot see is a scientific .
1. The lesson calls the atom the “hidden layer” under every classification. State what an atom is, and say how the atoms in an element are different from the atoms in a compound.
Put the four tools in order
A student holds up a piece of copper wire. Number the tools 1 to 4 in the order the lesson uses them to explain one substance. Then write what each tool tells you about the copper wire.
| Order (1–4) | Tool | What it tells you about copper wire |
|---|---|---|
| Use a model | ||
| Classify the matter | ||
| Draw the particle diagram | ||
| Write the symbol |
Sort it
Write each substance in the correct box. Each box gets exactly three substances.
Element
Compound
Mixture
Scenario: the particle detective
Ms Tran looked at five samples from the science prep room and wrote down what a particle diagram of each one would show. Use her notes to complete the table. The first row is done for you.
| Sample | What the particle diagram shows | Element, compound or mixture? | Symbol or formula |
|---|---|---|---|
| 1. Helium in a party balloon | Single atoms, all the same type, spread far apart | Element | He |
| 2. Ammonia gas | Identical particles; each has 1 nitrogen atom bonded to 3 hydrogen atoms | ||
| 3. Sugar dissolved in water | Two kinds of particle spread evenly; sugar particles are not bonded to water particles | ||
| 4. Sulfur powder | Only sulfur atoms, packed closely together | ||
| 5. Chlorine gas | Identical particles; each is 2 chlorine atoms bonded together |
Source: sample prep-room notes.
2. A student says Sample 5 must be a compound “because its particles are made of two atoms bonded together”. Use the table to explain why chlorine gas is an element.
3. Helium and ammonia are both colourless gases, so they look the same in a jar. Explain why looking at a sample is not enough to classify it, and which tool from the table settled the question.
4. Explain the difference between a compound and a mixture. Use table salt (NaCl) and granite (a rock made of grains of several different minerals) as your two examples, and describe what the particles are doing in each.
Fill the gap
atoms; element; compound; mixture; symbol; particle; model. Not used (2): nucleus, formula.
1. The smallest unit of an element. An element has one type of atom; a compound has atoms of different elements bonded in a fixed ratio. [2 marks: 1 atom, 1 difference]
Put the four tools in order
Reading down the table as printed: 4, 1, 3, 2. Classify: element (only copper atoms). Symbol: Cu. Particle diagram: identical Cu atoms packed in regular rows. Model: packed metal atoms explain why the wire conducts and bends instead of shattering.
Sort it
Element: oxygen gas (O₂), gold (Au), neon (Ne). Compound: glucose (C₆H₁₂O₆), carbon dioxide (CO₂), magnesium oxide (MgO). Mixture: air, sand mixed with iron filings, cordial drink.
Go Deeper
Table 1: 2. compound, NH₃. 3. mixture, no single formula (it contains sugar and H₂O). 4. element, S. 5. element, Cl₂.
2. All its atoms are chlorine; a compound needs different elements bonded together, so bonded pairs of one type of atom are still an element. [2 marks: 1 one type of atom, 1 compound needs different elements]
3. Appearance does not show the particles. The particle diagram settled it: helium is single identical atoms (element); ammonia is N and H atoms bonded (compound). [2 marks: 1 appearance hides the particles, 1 particle diagram named with the evidence]
Show What You Know
4. Marking guide: 1 a compound is different elements chemically bonded in a fixed ratio; 1 a mixture is more than one substance physically combined, not bonded; 1 NaCl: compound, sodium and chlorine bonded in a fixed 1:1 ratio; 1 granite: mixture, grains of different minerals side by side, amounts can vary, each keeps its identity. [4 marks]
Common error to watch for: thinking any formula with two atoms (O₂, Cl₂) means a compound. A compound needs two or more different elements.