Elements, Compounds and Mixtures: a full term of science

Ten ready-to-teach lessons for Year 8 Chemical sciences. Print this pack and the term is prepared: every lesson comes with a step-by-step plan, the questions to ask, a student worksheet, cut-out cards, an evidence sheet or exit tickets, an assessment kit and worked answers.

Start here: five minutes to Monday

1. Skim the term at a glance on the next page.
2. Print the lesson you need. Each lesson is three A4 sheets: plan, worksheet, and cards, an evidence sheet or tickets.
3. Gather the few items under “You need” on the plan. Most come from the science prep room, the kitchen or the art cupboard.
4. Open the free interactive unit on your board or projector. Every plan tells you which picture to show and when.
5. Teach straight from the plan. Timings, talk prompts, misconceptions and worked answers are all on the one page.

For any Year 8 science teacher

The pack suits a chemistry specialist and a teacher working outside their own subject alike: each plan explains the idea in plain words, lists the misconceptions students bring, and gives worked answers. The big idea of the term: every material is made from about a hundred kinds of atom. An element has one kind; a compound has two or more kinds joined in a fixed ratio, making a new substance; a mixture is substances together but not joined. Chemists show all of this in particle pictures, models, symbols and formulas, and each representation tells a different part of the story.

Two ways to run each lesson

Every lesson works as one 60-minute block, or as two 30-minute sessions; the split point is marked in every plan. Look ahead: Lesson 2 needs five element samples and a simple conductivity tester, Lesson 5 needs iron filings, sulfur and a lump of iron sulfide, and Lesson 6 needs 9 V batteries and baking soda.

Safety and care in one look

Eye protection goes on for the iron and sulfur. Sulfur and iron sulfide are handled with gloves or in sealed bags, and iron sulfide is kept away from acids. Water is split with a 9 V battery and baking soda only, never with mains power and never with table salt, and testing the gases with a splint is for the teacher only.

The term at a glance

One lesson a week for a term. Each lesson stands on the ones before it, so run them in order where you can.

How the sequence builds

Lesson 1 sorts matter into its three kinds at the particle level. Lessons 2 to 4 build the language of chemistry: symbols, models and formulas. Lessons 5 and 6 show what makes a compound special: a new substance that only a chemical reaction can make or split. Lesson 7 turns to the mixtures all around us, Lesson 8 compares the representations side by side, Lesson 9 follows Australian resources from the ground to the shelf, and Lesson 10 brings it together.

Curriculum links (Australian Curriculum V9)

The whole term teaches the Science Understanding descriptor AC9S8U06 quoted on the cover. The lessons also work these Science Inquiry and Human Endeavour descriptors:

Assessment in this pack

• Every plan ends with “Answers and look-fors”: what meeting the idea sounds like in a Year 8 voice, with working.
• The assessment sheet near the front has a class observation checklist and a three-level rubric.
• Lesson 10 is the summative pair: the lab inventory task, plus the “Show what we know” check.

Materials for the whole term

One gathering session covers all ten lessons. Most of it comes from the science prep room, the kitchen and the art cupboard. Two things are worth doing ahead: check the prep room has iron sulfide and sulfur for Lesson 5, and test one water-splitting cell before Lesson 6.

The one-trip list

• From the prep room: copper wire, sulfur, a graphite rod, magnesium ribbon, iron filings, iron sulfide, magnets, petri dishes, hand lenses, test tubes, eye protection and a periodic table.
• From the supermarket: baking soda, cling wrap, aluminium foil, paper plates and plastic cups.
• From the art cupboard: plasticine in five colours, pencils and a sharpener.
• From a hardware store: 9 V batteries, clip leads and a brass key or fitting.

Safety and care in one look

• Eye protection for the iron and sulfur; nobody breathes the powders or rubs their eyes.
• Sulfur and iron sulfide are handled with gloves or in sealed bags; iron sulfide is kept away from acids.
• Water is split with a 9 V battery and baking soda only: never mains power, never table salt.
• Testing gases with a lighted or glowing splint is for the teacher only; magnesium ribbon is never lit.

Assessment without extra work

The term assesses itself. Every lesson plan ends with worked answers and look-fors, and Lesson 10 is the summative pair: the lab inventory task, in which students classify six jars, read formulas and draw a model two ways, and the final check. This sheet is the place to note what you see along the way.

The three levels

Class observation checklist

A tick a lesson is plenty; the Lesson 10 task and check fill the gaps.

Word wall cards

Cut out the cards and build the wall as the words arrive: atom, element, molecule, compound and mixture in Lesson 1; symbol, periodic table, metal and non-metal in Lesson 2; formula in Lesson 3; subscript in Lesson 4; physical change and chemical reaction in Lesson 5; electrolysis in Lesson 6; pure substance and alloy in Lesson 7; structural diagram in Lesson 8; ore in Lesson 9.

Dear families

This term in science, Year 8 studies what everything is made of: elements, made of one kind of atom; compounds, in which different elements are joined into new substances; and mixtures, in which substances are simply together. Students learn the symbols and formulas chemists use, build models of molecules, and find out why salt, made from a dangerous metal and a poisonous gas, is safe to eat.

Along the way your student will test elements to see which are metals, build molecules from plasticine, pull iron out of a mixture with a magnet, split water into two gases with a battery, and follow Australian resources from the mine to the shop.

Try this at home

• Read the ingredients on a packet in the pantry. Which ingredients are compounds, and is the food a mixture?
• Look for products labelled pure. What does pure mean on the label, and what would it mean to a scientist?
• Find something made of brass, steel or gold jewellery. Why are most metal objects mixtures?
• Look at the formula on a bottle of something like hydrogen peroxide or baking soda, and count its atoms.

What to ask your scientist

• What is the difference between an element, a compound and a mixture?
• Why is oxygen gas an element, even though its molecules have two atoms?
• What does the 2 in H₂O mean?
• How did your class split water, and what came out?

A small note on care: students wear eye protection with powders, chemicals are handled in sealed bags or with gloves, and the only electricity used is a small 9 V battery.

Warm regards,

The Year 8 science team

Printed from the free seegongsik Elements, Compounds and Mixtures teaching pack · seegongsik.com/au/y8/chemical/AC9S8U06/pack

Element, compound or mixture?

Every material is made of atoms, and there are only about a hundred kinds of atom, one for each element. An element is made of only one kind of atom; its particles may be single atoms or molecules of two or more identical atoms. A compound is two or more different elements chemically joined in a fixed ratio, so every particle of it is the same. A mixture is two or more substances that are together but not joined, in any amounts. Pairs sort twelve particle pictures, asking two questions of each: how many kinds of atom, and is every particle the same?

We are learning to

• describe elements, compounds and mixtures at the particle level,
• classify a particle picture by asking how many kinds of atom it holds and whether every particle is the same,
• explain the difference between an atom, a molecule and a compound.

Success criteria

• I can sort the twelve cards and give the reason for each.
• I can explain why a molecule of two identical atoms is still an element.

You need

• the particle cards (third sheet), one set per pair, and the worksheet (next sheet), one per student,
• to show: a piece of copper wire, a cup of water and a cup of salty water.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening, the board and six cards in Session A, and the other six, Part B and Part C in Session B.

Watch for these ideas

• “Any molecule is a compound.” A molecule of two identical atoms, such as oxygen, is still an element.
• “A neat, regular pattern means a mixture of two things.” Salt is a compound with a regular pattern; a mixture has no fixed pattern or ratio.
• “A mixture has to contain elements.” Mixtures can hold compounds too: salty water is two compounds mixed.

Make it easier, make it bigger

• Easier: sort cards A, C and B first, one of each kind, then the rest.
• Bigger: draw a particle picture of a mixture of two elements and one compound, and explain why it is still a mixture.

Answers and look-fors

• Part A: element A, E, I, L; compound C, D, F, J, K; mixture B, G, H.
• Reasons: A: single atoms, all of one kind; B: two kinds of atom, mixed but not joined; C: every particle is the same pair of two different atoms; D: every particle is one large atom joined to two small ones of another kind; E: molecules of two atoms, all of one kind; F: every particle is the same row of three, two kinds of atom; G: two kinds of element molecule and a compound molecule, not joined to each other; H: two different compounds mixed together; I: atoms of one kind packed in rows; J: two kinds of atom packed in a regular pattern, always one to one; K: every particle is one atom joined to three of another kind; L: molecules of two atoms, all of one kind.
• Part B: an element has only one kind of atom; a compound has two or more kinds of atom chemically joined, the same in every particle; a mixture has two or more substances together but not joined, in any amounts.
• Part C: 1. An atom is the smallest particle of an element; a molecule is two or more atoms joined; a compound is a substance whose molecules (or patterns) hold two or more different kinds of atom. 2. Still an element: every atom is the same kind. 3. Card J: two kinds of atom joined in a fixed one to one pattern, the same all the way through.

Element, compound or mixture?

A. Twelve pictures

B. In our own words

C. Questions

What is in the box?

Cut out the cards. Each circle is an atom; each colour is a different element. Lay down the three grey heading cards and sort each card.

Teacher note: the piles are not the same size; the answer is on the plan.

Symbols for the elements

Each element has a symbol of one or two letters, the same in every language: the first letter is always a capital, and a second letter is always lower case, so Co is cobalt but CO is a compound of carbon and oxygen. Most symbols come from the English name, but some come from older Latin names: Na from natrium (sodium), K from kalium (potassium), Fe from ferrum (iron), Cu from cuprum (copper) and Au from aurum (gold). The periodic table lists every element in order. Most elements are metals, which are shiny, bend and conduct electricity; the non-metals mostly are not, and graphite is the famous exception. Groups test five elements, then pairs match symbol cards to name cards.

We are learning to

• use the symbols for common elements, with the capital and lower-case letters right,
• find elements on the periodic table,
• tell metals from non-metals by their properties.

Success criteria

• I can match twelve symbols to their names, including the ones from Latin.
• I can sort five elements into metals and non-metals from my test results.

You need

• for each group: copper wire, a sulfur lump in a small sealed bag or jar, aluminium foil, a graphite rod and magnesium ribbon; a simple tester (a battery, wires and a small globe or buzzer),
• a periodic table on the wall or one per pair, the worksheet (next sheet), one per student, and the cards (third sheet), one set per pair.

Safety: handle the sulfur with gloves or through its bag and wash hands afterwards; magnesium ribbon is only bent and tested, never lit.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening, the board and the tests in Session A, and the cards and Part C in Session B.

Watch for these ideas

• Writing CO for cobalt or NA for sodium: the second letter of a symbol is always lower case, and a capital starts a new element.
• “Every shiny element is a metal” or “only metals conduct”: graphite is a non-metal that is a little shiny and conducts.
• “An element’s symbol is the first letter of its name.” Many share a first letter, and some symbols come from Latin names.

Make it easier, make it bigger

• Easier: match the seven symbols that come from English names first (H, C, N, O, Mg, Al, Cl), then the rest with the hint list on the board.
• Bigger: find the symbols for silver, lead, tin and mercury on the periodic table, and look up the Latin name behind each.

Answers and look-fors

• Part A: copper (wire) Cu: shiny, reddish, bends, conducts, metal; sulfur (lump) S: dull yellow, crumbles, does not conduct, non-metal; aluminium (foil) Al: shiny, silver, bends, conducts, metal; carbon (graphite rod) C: grey, a little shiny, snaps, conducts, non-metal; magnesium (ribbon) Mg: shiny once rubbed clean, bends, conducts, metal. Metals: copper, aluminium, magnesium.
• Part B: name card 1 (magnesium) with symbol card I (Mg); name card 2 (copper) with symbol card J (Cu); name card 3 (hydrogen) with symbol card D (H); name card 4 (chlorine) with symbol card L (Cl); name card 5 (oxygen) with symbol card B (O); name card 6 (iron) with symbol card A (Fe); name card 7 (aluminium) with symbol card C (Al); name card 8 (nitrogen) with symbol card K (N); name card 9 (gold) with symbol card E (Au); name card 10 (carbon) with symbol card G (C); name card 11 (potassium) with symbol card H (K); name card 12 (sodium) with symbol card F (Na).
• Part C: 1. Carbon, as graphite (C), conducts electricity although it is a non-metal, so conducting alone does not prove an element is a metal. 2. From Latin names: Na (natrium, sodium), K (kalium, potassium), Fe (ferrum, iron), Cu (cuprum, copper), Au (aurum, gold). 3. Co is one element, cobalt; CO is two elements, carbon and oxygen, so it is a compound (carbon monoxide). 4. About three quarters of the elements are metals; they sit on the left and in the middle of the table, the non-metals on the right.
• Bigger: silver Ag (argentum), lead Pb (plumbum), tin Sn (stannum), mercury Hg (hydrargyrum).

Symbols for the elements

A. Five elements

B. Symbols and names

Write the letter of the symbol card under each name card’s number.

C. Questions

Match the symbol to the name

Cut out all the cards. Match each symbol card (a letter) to its name card (a number).

Symbol cards

Name cards

Teacher note: the two sets are printed in different orders; the matches are on the plan.

Molecules from models

A molecule is two or more atoms joined together. Models let us see molecules we could never see directly. In model kits each element has its own colour: hydrogen white, carbon black, oxygen red, nitrogen blue and chlorine green. Atoms have no colour of their own; the colours only tell the elements apart. Students build eight molecules from plasticine balls pressed together, sketch each one, decide whether it is an element or a compound, and write its formula: the symbols of its atoms, with a small number after each symbol that appears more than once.

We are learning to

• build models of molecules and sketch them,
• tell element molecules from compound molecules,
• write a simple formula from a model.

Success criteria

• I can build all eight molecules and sort them into elements and compounds.
• I can write the formula for each, and say what a model shows and what it leaves out.

You need

• for each pair: plasticine in five colours (or a molecular model kit), and a paper plate to build on,
• the worksheet (next sheet), one per student, and the exit tickets (third sheet).

Make hydrogen balls about the size of a pea, carbon, nitrogen and oxygen balls a little bigger than a marble, and chlorine balls bigger again.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening, the board and four molecules in Session A, and four molecules and Part B in Session B.

Watch for these ideas

• “Atoms are coloured like the model.” The colours are a code so we can tell elements apart; atoms have no colour.
• “Every molecule is a compound.” Hydrogen, oxygen and chlorine molecules each have one kind of atom, so they are elements.
• “The model shows exactly what a molecule looks like.” Real molecules vibrate, are far too small to see, and have no solid surface.

Make it easier, make it bigger

• Easier: build water, hydrogen, oxygen and methane only, with the balls counted out for each.
• Bigger: build hydrogen peroxide, two hydrogen and two oxygen atoms in a chain. It has the same elements as water. Is it the same substance?

Answers and look-fors

• Part A: water, compound, H2O; hydrogen, element, H2; carbon dioxide, compound, CO2; methane, compound, CH4; oxygen, element, O2; ammonia, compound, NH3; chlorine, element, Cl2; hydrogen chloride, compound, HCl.
• Part B: 1. hydrogen, oxygen, chlorine: every atom in the molecule is the same kind. 2. Methane has 5 atoms but only two kinds, carbon and hydrogen; the number of elements counts kinds of atom, not atoms. 3. A model shows which atoms there are, how they are joined and roughly the shape; it does not show the real size, that atoms have no colour, or that molecules are always moving.
• Bigger: no; hydrogen peroxide (H₂O₂) has a different ratio of the same atoms, so it is a different compound with different properties: it is used as a bleach.
• Exit tickets: 1. Chlorine is two green balls (an element); hydrogen chloride is one white and one green (a compound). 2. Four: one nitrogen and three hydrogen. 3. Both its atoms are oxygen, one kind of atom.

Molecules from models

Model colours: hydrogen white, small; carbon black; oxygen red; nitrogen blue; chlorine green, large.

A. Eight molecules

B. Questions

Exit tickets

Cut out one ticket for each student.

Reading formulas

A chemical formula lists the symbol of each element in a substance. A small number written below the line after a symbol, the subscript, says how many atoms of that element there are; no number means one. Each capital letter starts a new element, so CaCO₃ is one calcium, one carbon and three oxygen atoms. A formula with only one symbol, such as O₃ or S₈, is an element however big its number; two or more different symbols make a compound. Students count atoms in six formulas, decide element or compound from six more, and write formulas from words.

We are learning to

• read the elements and the number of each atom from a formula,
• decide from a formula whether a substance is an element or a compound,
• write a formula from a description.

Success criteria

• I can count the atoms of each element in a formula, including glucose.
• I can explain the difference between Co and CO, and between 2H and H₂.

You need

• the worksheet (next sheet), one per student, and the exit tickets (third sheet); a periodic table on the wall,
• for the relay: mini whiteboards or scrap paper, one per team.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening, the board and Part A in Session A, and Part B, the relay and Part D in Session B.

Watch for these ideas

• Reading a subscript as belonging to the next symbol: in CO₂ the 2 counts the oxygen, the symbol in front of it.
• Reading CO as cobalt, or NaCl as four elements: each capital letter starts a new element.
• “O₃ has three atoms, so it must be a compound.” It has one kind of atom, so it is an element (ozone).

Make it easier, make it bigger

• Easier: underline each capital letter first, then count element by element.
• Bigger: in Ca(OH)₂, the 2 after the bracket doubles everything inside it. How many atoms of each element are there?

Answers and look-fors

• Part A: H2O: 2 H, 1 O, 3 atoms; CH4: 1 C, 4 H, 5 atoms; NaCl: 1 Na, 1 Cl, 2 atoms; CaCO3: 1 Ca, 1 C, 3 O, 5 atoms; C6H12O6: 6 C, 12 H, 6 O, 24 atoms; H2SO4: 2 H, 1 S, 4 O, 7 atoms. The biggest is glucose, with 24.
• Part B: O3 (ozone) element, CO (carbon monoxide) compound, S8 (sulfur) element, Co (cobalt) element, NO2 (nitrogen dioxide) compound, N2 (nitrogen) element.
• Part C: one carbon atom and two oxygen atoms: CO2; two nitrogen atoms: N2; one sulfur atom and three oxygen atoms: SO3; one calcium atom and two chlorine atoms: CaCl2.
• Part D: 1. 2H is two separate hydrogen atoms; H₂ is one molecule of two hydrogen atoms joined. 2. Both have hydrogen and oxygen, but glucose also has carbon, and the atoms are joined in different numbers and patterns, so they are different compounds.
• Bigger: Ca(OH)₂ has 1 calcium, 2 oxygen and 2 hydrogen atoms: 5 in all.
• Exit tickets: 1. 1 Ca, 1 C, 3 O. 2. An element: only one kind of atom (sulfur). 3. NO₂.

Reading formulas

A. Counting atoms

B. Element or compound?

C. Write the formula

D. Questions

Exit tickets

Cut out one ticket for each student.

A compound is a new substance

When elements join to form a compound, the result is a new substance with properties of its own, often nothing like the elements it came from: sodium, a metal that reacts violently with water, and chlorine, a poisonous gas, make table salt. In a compound the elements are joined in a fixed ratio (iron sulfide is always one iron atom for every sulfur atom), and no physical method can pull them apart. A mixture is different: its parts keep their own properties, can be mixed in any amounts, and can be separated again. Groups mix iron filings with sulfur and separate them with a magnet, then compare the mixture with a sample of the compound, iron sulfide.

We are learning to

• compare the properties of a mixture of elements with the compound they form,
• explain that a compound has a fixed ratio of elements and new properties,
• explain why a compound cannot be separated by a physical method.

Success criteria

• I can give three differences between a mixture of iron and sulfur and iron sulfide.
• I can use the evidence sheet to show that a compound is not like its elements.

You need

• for each group: a petri dish, a teaspoon of iron filings, a teaspoon of sulfur powder, a magnet wrapped in cling wrap, a hand lens and eye protection,
• a lump of iron sulfide from the prep room in a sealed clear bag, passed round the class,
• the worksheet (next sheet) and the evidence sheet (third sheet), one each per student.

Safety: eye protection on; do not breathe the powders or rub your eyes; keep iron sulfide away from acids, which turn it into a poisonous gas; wash hands at the end.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening, the board and the magnet in Session A, and Part B and the evidence sheet in Session B.

Watch for these ideas

• “A compound has the properties of its elements.” It is a new substance: iron sulfide is not magnetic and not yellow.
• “Stirring two elements together makes a compound.” Mixing only makes a mixture; a compound forms in a chemical reaction.
• “A strong enough magnet could pull the iron out of iron sulfide.” Its iron atoms are joined to sulfur atoms; only a chemical reaction can separate them.

Make it easier, make it bigger

• Easier: do the magnet and the iron sulfide together as a class, and fill in Part B as a group.
• Bigger: in iron sulfide, 56 g of iron is always joined to 32 g of sulfur. How much sulfur joins with 14 g of iron?

Answers and look-fors

• Part A: iron, grey and pulled by the magnet; sulfur, yellow and not pulled; the mixture, grey and yellow specks you can still see apart, and the magnet pulls the iron out and leaves the sulfur; iron sulfide, a dark grey to black solid that the magnet does not pull.
• Part B: mixture: yes; yes; any amounts; still like iron and sulfur. Compound: no; no; fixed, one iron atom for every sulfur atom (FeS); something new.
• Part C: 1. The magnet separated them, so the iron and the sulfur were only mixed, not joined. 2. In iron sulfide each iron atom is joined to a sulfur atom, so the substance no longer behaves like iron. 3. Heating the mixture, a chemical reaction; this is done by the teacher in a fume cupboard, or watched on video, because it gives off a harmful gas.
• Evidence sheet: 1. For example sodium chloride: a dangerous metal and a poisonous gas make a white solid we eat. 2. Water is a new substance: its atoms are joined into new molecules with properties of their own. 3. Dissolving and evaporating are physical: they separate salt from water but cannot break the joins between sodium and chlorine; that needs a chemical reaction (electricity through melted salt).
• Bigger: 14 is a quarter of 56, so a quarter of 32 g: 8 g of sulfur.

A compound is a new substance

A. Iron, sulfur and a magnet

B. Mixture or compound?

C. Questions

Not like the elements at all

Each row shows two elements and the compound they make when they join.

Splitting a compound

No physical method can separate a compound, but a chemical reaction can. Passing electricity through water splits water molecules apart, and the atoms join up again as hydrogen gas at one electrode and oxygen gas at the other. Because every water molecule has two hydrogen atoms for each oxygen atom, about twice as much hydrogen comes off as oxygen. The formula predicts what we measure. Groups (or the teacher at the front) run a simple cell: water with a little baking soda so that it conducts, two pencils sharpened at both ends as electrodes, and a 9 V battery, with a small test tube of the solution upside down over each pencil lead to catch the gas.

We are learning to

• describe how a compound can be split by a chemical reaction,
• use a formula to predict the amounts of the elements it splits into,
• represent a reaction with particle pictures.

Success criteria

• I can use the results to show that about twice as much hydrogen as oxygen is made.
• I can link the 2 in H₂O to the volumes of the two gases.

You need

• for each group: a plastic cup of water with a teaspoon of baking soda stirred in, two pencils sharpened at both ends, a 9 V battery, two leads with clips, two small test tubes and a ruler or a measuring cylinder to read the gas volumes,
• the worksheet (next sheet), one per student, and the exit tickets (third sheet).

Safety: use a 9 V battery only, never mains power; use baking soda, never table salt, which makes poisonous chlorine gas; keep the pencil leads apart. Testing the gases with a lighted or glowing splint is for the teacher only.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening, the board and the cell in Session A, and Parts B to D in Session B.

Watch for these ideas

• “The bubbles are air, or steam.” They are new substances, hydrogen and oxygen, made from the water molecules.
• “The electricity turns into the gases.” The electricity supplies the energy to break the molecules apart; the atoms come from the water.
• “Water is hydrogen and oxygen mixed together.” In water the atoms are joined into molecules; the gases appear only when those molecules are split.

Make it easier, make it bigger

• Easier: watch one cell at the front, count the bubbles at each pencil for a minute, and use the example results for the graph.
• Bigger: hydrogen burns to make only water. Where could the electricity for splitting water come from, so that the hydrogen adds no carbon dioxide to the air?

Answers and look-fors

• Part A: hydrogen ÷ oxygen = 2.1, 2.1, 2.1, 2.1: about 2 every time. The pencil joined to the negative end of the battery makes the hydrogen.
• Part B: two straight lines from the origin, the hydrogen line about twice as steep.
• Part C: 4 water molecules hold 8 hydrogen atoms and 4 oxygen atoms, which make 4 hydrogen molecules (H₂) and 2 oxygen molecules (O₂): twice as many hydrogen molecules, so twice the volume of gas.
• Part D: 1. Every water molecule has two hydrogen atoms for each oxygen atom. The example ratio is a little over 2 (2.1) because a little oxygen dissolves in the water or reacts with the pencil lead. 2. Chemical: new substances (two gases) are made from the water, and the molecules are broken apart. 3. Salt in the water would make chlorine, a poisonous gas, at one pencil.
• Bigger: from solar panels or wind turbines; hydrogen made this way is often called green hydrogen, and Australia is building plants to make it.
• Exit tickets: 1. Hydrogen and oxygen. 2. About 5 mL of oxygen. 3. Filtering is physical; it cannot break the joins between the hydrogen and oxygen atoms in water molecules.

Splitting a compound

A. Gas collected (mL)

B. Graph

Plot both gases on the same axes, join each set of points, and add a key.

C. Before and after

Draw 4 water molecules, then draw what their atoms make after splitting.

D. Questions

Exit tickets

Cut out one ticket for each student.

Mixtures all around us

Most of the materials around us are mixtures: air, sea water, milk, tap water and most metal objects, which are alloys such as brass, steel and the gold in jewellery. In everyday talk “pure” means nothing harmful added, but to a scientist a pure substance is a single element or a single compound, the same all the way through. A mixture can hold elements and compounds together, and its make-up can vary: air is mostly nitrogen and oxygen, but how much water vapour it holds changes from day to day. Pairs sort twelve everyday materials, then draw a pie chart of air and work out how pure jewellery gold is.

We are learning to

• classify everyday materials as elements, compounds or mixtures,
• explain the difference between the everyday and the scientific meaning of pure,
• represent the make-up of a mixture with a pie chart.

Success criteria

• I can sort the twelve materials and give the clue that decided each one.
• I can explain why air and brass are mixtures, not compounds.

You need

• the material cards (third sheet), one set per pair, and the worksheet (next sheet), one per student; protractors,
• to show: a brass key or fitting and a piece of copper wire, and a bottle labelled “pure” spring water or juice.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening, the board and the cards in Session A, and the label, the pie chart and Part C in Session B.

Watch for these ideas

• “Pure means natural, or nothing added.” To a scientist, pure means one substance only; pure orange juice is a mixture of hundreds.
• “Air is a compound of nitrogen and oxygen.” The gases are not joined, and the amounts can vary, so air is a mixture.
• “An alloy is a compound of metals.” Brass can hold anything from 5% to 45% zinc; a compound would have a fixed ratio.

Make it easier, make it bigger

• Easier: sort cards A to F first, then the rest.
• Bigger: why are wedding rings rarely made of 24 carat gold? What would you test to compare 24 carat and 18 carat gold?

Answers and look-fors

• Part A: element C, D, H; compound A, G, I, K; mixture B, E, F, J, L. Clues: a single symbol is an element; a formula with two or more symbols, or a fixed ratio, is a compound; several substances or amounts that vary is a mixture.
• Part B: nitrogen 78% (about 281 degrees), oxygen 21% (about 76 degrees), argon 0.9%, carbon dioxide and others 0.1%; the last two make one thin slice together, about 4 degrees.
• Part C: 1. A mixture: it holds two elements (nitrogen, oxygen), a third (argon) and a compound (carbon dioxide), none joined to each other, in amounts that can vary. 2. It is many substances mixed (water, sugars, acids, flavours); pure on the label means nothing added. 3. Distilled water is a pure compound; tap water is a mixture, with minerals and chlorine dissolved in it. 4. 18 ÷ 24 = 75% gold, mixed with other metals, so it is a mixture (an alloy); 9 carat is 37.5% gold.
• Bigger: pure gold is very soft and scratches and bends easily; alloys are harder. Compare them with a scratch test or a bend test.

Mixtures all around us

A. Twelve materials

B. What is in air?

C. Questions

Element, compound or mixture?

Cut out the cards. Lay down the three grey heading cards, read each card, and sort it.

Teacher note: the piles are not the same size; the answer is on the plan.

One substance, many representations

Chemists show the same substance in several ways, and each carries different information. A formula counts the atoms of each element in the fewest characters. A 2D structural diagram uses the element symbols and a line for each bond, so it shows which atoms are joined (a double line is a double bond), but it flattens the molecule onto the page. A 3D model shows the real shape and the relative sizes of the atoms, in the model-kit colours. Pairs match fifteen cards into five sets of three, one set for each substance, then compare what each representation shows and leaves out.

We are learning to

• move between formulas, 2D structural diagrams and 3D models of the same substance,
• compare what each representation shows and what it leaves out,
• draw a simple molecule in two ways.

Success criteria

• I can match all fifteen cards into the five sets, and name each substance.
• I can say which representation I would use to count atoms, to show bonds and to show shape.

You need

• the model cards (third sheet), one set per pair, and the worksheet (next sheet), one per student,
• a molecular model kit or plasticine for the opening, if you have it.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening, the board and the cards in Session A, and Parts B to D in Session B.

Watch for these ideas

• “Different pictures mean different substances.” Each set of three is one substance shown three ways.
• “The 2D diagram shows the real shape.” Methane is drawn flat as a cross, but the real molecule is a pyramid with a triangle base.
• “The formula shows how the atoms are joined.” It only counts them: CO₂ does not say the carbon sits in the middle.

Make it easier, make it bigger

• Easier: start with the formula cards, and find the 2D and 3D cards that match each one.
• Bigger: ethanol is C₂H₆O. Draw a 2D diagram in which each carbon makes four bonds, the oxygen two and each hydrogen one.

Answers and look-fors

• Part A: water (H2O): 2D C, 3D G, formula O; carbon dioxide (CO2): 2D E, 3D I, formula M; methane (CH4): 2D A, 3D J, formula N; ammonia (NH3): 2D D, 3D F, formula L; oxygen (O2): 2D B, 3D H, formula K.
• Part B: formula: elements yes, how many yes, joined no, shape no. 2D diagram: elements yes, how many yes, joined yes, shape only roughly. 3D model: elements yes (by the colour code), how many yes, joined yes, shape yes, and the relative sizes too.
• Part C: H–Cl, one line between the symbols; the model is a small white ball joined to a larger green ball.
• Part D: 1. The formula. 2. The shape of a molecule decides how it fits with other molecules and how the substance behaves; a 2D diagram hides it. 3. Two lines are a double bond: the carbon and each oxygen are joined twice over.
• Bigger: H₃C–CH₂–O–H drawn out, with every hydrogen shown: two carbons in a row, the oxygen on the second carbon and a hydrogen on the oxygen.

One substance, many representations

A. Five sets

B. What does each one show?

Write yes, no or roughly.

C. Draw it two ways

Hydrogen chloride, HCl: a hydrogen atom joined to a chlorine atom.

D. Questions

Five substances, fifteen cards

Cut out the cards and match them into five sets of three: a 2D diagram, a 3D model and a formula for the same substance.

3D model colours: hydrogen white, carbon black, oxygen red, nitrogen blue.

Teacher note: each set of five is printed in a different order; the matches are on the plan.

From the ground to the shelf

Australia digs up and pumps out some of the world’s most important materials, and almost all of them come out of the ground as mixtures: ores are useful compounds or elements mixed with other rock, and natural gas is several gases together. Processing takes them apart in two kinds of step. Physical steps such as crushing, washing, dissolving and evaporating separate mixtures. Chemical steps, such as heating iron oxide with carbon in a blast furnace or passing electricity through melted alumina, split compounds into elements. Pairs read six resource cards, classify each resource as it is mined and as it is sold, and weigh up what processing costs.

We are learning to

• classify resources as elements, compounds or mixtures, as they are mined and as they are sold,
• tell the physical steps that separate a mixture from the chemical steps that split a compound,
• consider the impacts of mining and processing.

Success criteria

• I can complete the table for all six resources, with a formula for each product.
• I can explain why getting iron from iron ore needs a chemical reaction, and name one impact of processing.

You need

• the resource cards (third sheet), one set per pair, the worksheet (next sheet), one per student, and a map of Australia,
• if you have them: samples of ore, salt crystals and aluminium foil to pass round.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening, the board and three cards in Session A, and three cards and Part B in Session B.

Watch for these ideas

• “Gold nuggets are pure gold.” Even nuggets hold some silver; refining makes the element.
• “Mines dig up metals ready to use.” Most metals are found joined to other elements in compounds, which must be split by a chemical reaction.
• “Processing is just cleaning.” Some steps are physical, but splitting a compound is a chemical change that needs a lot of energy.

Make it easier, make it bigger

• Easier: do gold, salt and natural gas first; their steps are the simplest.
• Bigger: aluminium cans are easy to recycle and recycling uses far less energy than making new aluminium. Use the bauxite card to explain why.

Answers and look-fors

• Part A: bauxite (Weipa, Qld): mined as a mixture; sold as alumina (aluminium oxide), a compound, Al2O3; gold (Kalgoorlie, WA): mined as a mixture; sold as gold, an element, Au; natural gas (Bass Strait, Vic): mined as a mixture; sold as methane, a compound, CH4; salt (Shark Bay, WA): mined as a mixture; sold as sodium chloride, a compound, NaCl; iron ore (Pilbara, WA): mined as a mixture; sold as iron, an element, Fe; lithium (Greenbushes, WA): mined as a mixture; sold as lithium hydroxide, a compound, LiOH.
• Part B: 1. Rock forms from many substances at once, and the useful ones are spread through it; even sea water and natural gas are mixtures. 2. Iron oxide is a compound: iron atoms joined to oxygen atoms. Crushing and washing only separate the ore from other rock; taking the oxygen away needs a chemical reaction with carbon in a blast furnace. 3. Answers vary: for example, mines and refineries clear land, use water and a lot of energy, and the blast furnace releases carbon dioxide; recycling, renewable electricity and repairing the land after mining reduce the impact.
• Products: elements gold and iron; compounds alumina (aluminium oxide), methane, sodium chloride, lithium hydroxide.
• Bigger: making new aluminium means splitting aluminium oxide with huge amounts of electricity; a recycled can is already the element and only needs melting.

From the ground to the shelf

A. Six resources

B. Questions

Six Australian resources

Read each card. Find the place on a map of Australia.

Show what we know

The last lesson brings the term together in a lab stocktake. Students classify six jars from pictures of their particles, read three formulas from jar labels, draw a 3D model as a 2D diagram and a formula, and explain a common mistake. Then each student sits the final check on their own, and the class finishes with the unit quiz on the board.

We are learning to

• classify matter as elements, compounds or mixtures from evidence,
• move between particle pictures, models, symbols and formulas,
• show what we know about the term on our own.

Success criteria

• I can classify all six jars and give the reason for each.
• I can back each answer on the final check with a particle picture, a formula or a reason.

You need

• the lab inventory task (next sheet) and the final check (third sheet), one each per student,
• the interactive unit open for the closing quiz.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the task and the partner check in Session A, and the final check and the class quiz in Session B.

Watch for these ideas

• Calling jar F a mixture because it has two kinds of atom: its fixed, regular one to one pattern makes it a compound.
• Calling jar A a compound because its particles are molecules: they have only one kind of atom.
• Counting NaHCO₃ as four atoms, one for each letter group: count each element’s atoms, then add.

Make it easier, make it bigger

• Easier: give the two questions (how many kinds of atom? are they joined, and is every particle the same?) at the top of the task.
• Bigger: draw a particle picture of a mixture that contains two elements and a compound, and label each part.

Answers and marking guide

• Task A: A element: molecules of three atoms, all of one kind; B compound: every particle is the same group of three kinds of atom; C mixture: molecules of one element, single atoms of another and pairs of a compound, none joined to each other; D mixture: two different compounds mixed together; E element: molecules of two atoms, all of one kind; F compound: two kinds of atom in a regular one to one pattern.
• Task B: propane, the gas in barbecue bottles, C3H8: 3 C, 8 H, 11 atoms; baking soda, NaHCO3: 1 Na, 1 H, 1 C, 3 O, 6 atoms; hydrogen peroxide, H2O2: 2 H, 2 O, 4 atoms.
• Task C: N with three lines to three H; the formula NH₃; the elements nitrogen and hydrogen; it is a compound.
• Task D: ozone has only one kind of atom, oxygen, so it is an element; being a molecule does not make a substance a compound. A compound needs two or more different elements joined.
• Check: 1. O2. 2. A mixture’s substances are not joined and can be in any amounts, like air or salty water; a compound’s elements are joined in a fixed ratio, like water. 3. 5. 4. Element: one kind of atom; compound: every particle the same, two or more kinds of atom joined; mixture: two or more different particles, not joined.
• Check: 5. a mixture. 6. CO₂, carbon dioxide, 3 atoms. 7. Any two of: it is not pulled by a magnet; it does not look like yellow sulfur or grey iron; its iron and sulfur are in a fixed ratio; it cannot be separated by a physical method. 8. The 3D model shows the bent shape and the relative sizes of the atoms; the formula shows quickly how many of each atom there are.
• Scoring: 1 mark each for 1, 3 and 5; 2 marks each for 2, 4, 6, 7 and 8. The rubric near the front of the pack turns the task and the check into a level.

The lab inventory

The prep room needs its jars sorted. Each circle is an atom; each colour is a different element.

A. Sort the jars

B. Read the labels

C. Draw it two ways

D. Explain

Show what we know

Show what you know about elements, compounds and mixtures. Read each item, then circle or write.

Teacher note: the marking guide is on this lesson’s plan; the rubric near the front of the pack turns the score into a level.