Chemistry 11–12 · Year 11

A circus of reaction types: synthesis, decomposition, combustion, precipitation, acid-base and acid-carbonate

Module 3: Reactive Chemistry

PracticalMedium risk

School laboratory, not for home

In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.

The idea

Chemical change shows itself as a new substance with new properties (a gas, a precipitate, a colour change, a temperature change or light), and each reaction type has a predictable product pattern.

Safety card

Medium riskLearners carry it out, with a teacher supervising

Setting: In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.

Hazards

magnesium flare
hot glass
suck-back of cold limewater into the hot boiling tube can crack it
silver nitrate is corrosive and stains skin; 0.1 mol/L sodium hydroxide is an irritant
ethanol is flammable
1 mol/L hydrochloric acid irritant

Controls

teacher lights the ethanol; no ethanol bottle open near a flame
delivery tube lifted out of the limewater before the heat is removed from the boiling tube
silver and copper wastes collected in labelled containers
well-plate volumes only for precipitation
eye protection
do not look directly at burning magnesium

Note

NSW Department of Education Chemical Safety in Schools (CSIS) package, 2021 Technical Update: Section 1.7 (risk assessment) and Volume 2 Appendix D (generic assessment advice and DoE chemical categories); record a RiskAssess (riskassess.com.au) risk assessment before the lesson and check the school's hazardous chemical register (CSIS Section 1.9) for local restrictions.

What you need

Station 1 synthesis: 3 cm magnesium ribbon, tongs, Bunsen burner
Station 2 decomposition: 1 g copper(II) carbonate in a boiling tube, delivery tube into 5 mL limewater
Station 3 combustion: 1 mL ethanol on a watch glass (teacher lights it), cold dry beaker inverted above it, limewater
Station 4 precipitation: 0.1 mol/L copper(II) sulfate 2 mL and 0.1 mol/L sodium hydroxide 2 mL in a well plate; 0.1 mol/L silver nitrate and 0.1 mol/L sodium chloride
Station 5 acid-base: 0.1 mol/L hydrochloric acid 5 mL, 0.1 mol/L sodium hydroxide 5 mL, universal indicator, temperature probe or digital thermometer reading to 0.1 degrees Celsius, because the rise is under one degree
Station 6 acid-carbonate: marble chip (calcium carbonate) 1 g, 1 mol/L hydrochloric acid 5 mL, limewater, balance

How to do it

At each station record the appearance of the reactants, what is observed during the reaction, and the appearance of the products; note any temperature change with the 0.1 degree probe where liquids are used.
Station 1: hold the magnesium in the flame with tongs and record the light and the product's colour and texture.
Station 2: heat the green copper(II) carbonate gently and bubble the gas through limewater; before removing the flame, lift the delivery tube out of the limewater so cold limewater cannot be sucked back into the hot tube; record the colour change of the solid and of the limewater.
Station 3: watch the teacher burn the ethanol; record condensation on the cold beaker and the limewater test on the gas collected.
Station 4: mix the two ionic solutions drop by drop and record the precipitate colour; repeat for silver nitrate and sodium chloride.
Station 5: add hydroxide to acid with indicator until the colour changes; record the temperature before and after.
Station 6: weigh the marble chip and acid before mixing, react, reweigh after two minutes and test the gas with limewater.
Classify each reaction, write a word equation and a balanced formula equation, and list the indicator of chemical change seen at each station.

What you should see

Magnesium burns with a bright white light to a white powder (2 Mg + O2 gives 2 MgO). Copper(II) carbonate turns black (copper(II) oxide) and the gas turns limewater milky (CuCO3 gives CuO + CO2; the laboratory reagent is basic copper(II) carbonate, CuCO3.Cu(OH)2, which also gives off water). Ethanol burns with a blue flame, water condenses on the cold glass and the gas clouds limewater. Copper(II) sulfate and sodium hydroxide give a pale blue precipitate (Cu(OH)2); silver nitrate and sodium chloride give a white precipitate (AgCl) that greys in light. Acid plus hydroxide changes the indicator through green to blue; 5 mL of each at 0.1 mol/L forms only 0.5 mmol of water, so the rise is at most 0.67 degrees Celsius (55.8 kJ per mole of water, 10 g of solution), easiest to see with a 0.1 degree probe. Marble and acid fizz, the limewater clouds and the open system loses mass: 5 mL of 1 mol/L acid can consume at most 0.25 g of marble and release 0.11 g of CO2 (0.44 g of CO2 per gram of marble consumed).

What changes

This activity lists no variables to change, measure and keep the same.

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

A colour change always means a chemical reaction (dissolving a coloured salt also changes colour; look for a new substance).
Bubbles in boiling water show a chemical change (that is a physical change; the bubbles are water vapour).
The precipitate came from the water (it forms from ions already present in the two solutions).

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Chemistry Stage 6 Syllabus (2017), NESA; the current syllabus, taught in 2026 (codes read from the syllabus document)CH11-10 CH11/12-3 CH11/12-4
Chemistry Stage 6 Syllabus (2017), NESA; the current syllabus, taught in 2026 (codes read from the syllabus document); a Working Scientifically outcome not among those the syllabus targets in Module 3, which it allows in any moduleCH11/12-7
Chemistry 11-12 Syllabus (2025), NESA; implemented from 2028, not yet taughtCH-11-03 CH-11WS-03
Australian Curriculum v9No Australian Curriculum v9 code is listed.

Sources

The pages the author read to write this activity.

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