Year 7 Science · Unit 2 · Lesson 13

Unit 2 Synthesis

Foundation Worksheet

Name

Date

Class

Learning Goals

Recall the key words for substances, mixtures and solutions.
Classify samples of matter using the matter family tree.
Use melting and boiling points to predict and explain states of matter.

Warm Up

Fill the gap

Choose the correct word from the word bank. Each word is used at most once. Two words are not needed: cross them out.

solution particles element evaporation dilute solute compound solvent saturated mixture

All matter is made of tiny . A pure substance made of only one type of atom is an , and a pure substance made of two or more types of atom chemically bonded together is a . When substances are only physically combined, the result is a . When sugar dissolves evenly in water, the sugar is the and the sweet liquid is a . If no more sugar will dissolve at that temperature, the liquid is . To get dissolved salt back from salt water, you can use .

1. Filtration and distillation both separate mixtures. Name the property of the mixture that each technique depends on.

Recall 2 marks

Your Turn

Sort it: the matter family tree

Write each sample in the correct box. The boxes do not hold the same number of items.

glucose (C₆H₁₂O₆) air pure copper wire muesli carbon dioxide (CO₂) salt water oxygen gas (O₂) sand stirred into water table salt (NaCl) salt and pepper pure gold (Au) pure water (H₂O)

Element

Compound

Homogeneous mixture

Heterogeneous mixture

Complete the particle model table

Write the missing descriptions in the blank cells.

Recall 3 marks

State	How the particles are arranged	How the particles move	Shape and volume
Solid	close together, in a regular pattern
Liquid		slide and flow past each other
Gas			no fixed shape or volume

Go Deeper

Read the data: melting and boiling points

Scenario: solid, liquid or gas?

A substance is a solid below its melting point, a liquid between its melting point and its boiling point, and a gas above its boiling point. Room temperature is about 25 °C.

Table 1. Melting and boiling points of five pure substances

Substance	Melting point (°C)	Boiling point (°C)
Oxygen	−219	−183
Ethanol (alcohol)	−114	78
Water	0	100
Table salt	801	1465
Iron	1538	2862

Source: published values, rounded to the nearest degree.

2. Use Table 1 to give the state of oxygen, ethanol and iron at room temperature.

Apply 3 marks

3. On a winter night at an Antarctic base the air can reach −60 °C. Which substance in Table 1 would still be a liquid outdoors? Explain, and describe what happens to the particles of water as it freezes.

Analyse 3 marks

Show What You Know

4. Draw the matter family tree, from “Matter” at the top down to its four bottom boxes. Write one example in each bottom box. Then explain the difference between an element and a compound.

Analyse 6 marks

Answer Key (for teachers)

Fill the gap

particles; element; compound; mixture; solute; solution; saturated; evaporation. Not used: dilute, solvent.

Question 1

Filtration: particle size (an insoluble solid is too big to pass through the paper) (1). Distillation: different boiling points (1). [2 marks]

Sort it: the matter family tree

Element: pure copper wire; oxygen gas (O₂); pure gold (Au). Compound: glucose (C₆H₁₂O₆); carbon dioxide (CO₂); table salt (NaCl); pure water (H₂O). Homogeneous mixture: air; salt water. Heterogeneous mixture: muesli; sand stirred into water; salt and pepper.

Complete the particle model table

1 mark per row, both cells. Solid: vibrate in place; fixed shape and volume. Liquid: close but not in a pattern; no fixed shape, fixed volume. Gas: far apart, random; move quickly in all directions. [3 marks]

Question 2

Oxygen: gas, as 25 °C is above its boiling point (1). Ethanol: liquid, as 25 °C is between −114 and 78 °C (1). Iron: solid, as 25 °C is below its melting point (1). [3 marks]

Question 3

Ethanol (1): −60 °C is between its melting point (−114 °C) and boiling point (78 °C); water freezes at 0 °C (1). Water particles lose energy and slow down until the attractions lock them into fixed places (1). [3 marks]

Question 4

Marking guide: 1 Matter splits into pure substances and mixtures; 1 pure substances into elements and compounds, and mixtures into homogeneous and heterogeneous; 2 examples (all four correct = 2, two or three = 1); 1 an element has only one type of atom; 1 a compound has two or more types of atom chemically bonded, and cannot be separated by physical means. [6 marks]

Model answer: Matter → pure substance (element: gold; compound: water) and mixture (homogeneous: salt water; heterogeneous: muesli). An element has only one type of atom. A compound has two or more types of atom chemically bonded, so filtering or evaporating cannot split it.

Common error: calling a compound a mixture because it contains more than one element.