Bonding in Solids Virtual Lab: Identify Unknown Solids

This bonding in solids virtual lab follows the AP Chemistry lab where students get unlabeled white solids and must work out the bonding in each one from its properties. It also fits the AQA GCSE topic on how structure and bonding explain properties. Students heat each sample, test whether it dissolves in water and in hexane, and test conductivity as a solid, as a melt and in solution. They also strike it with a hammer. They fill in a property table, classify each unknown as ionic, simple molecular, metallic or giant covalent, and choose a reason. Then Check marks both.

Curriculum links

• AP Chemistry Unit 2 (topics 2.3 Structure of Ionic Solids and 2.4 Structure of Metals and Alloys) and Unit 3, topic 3.2 Properties of Solids. Also the AP Chemistry lab on identifying the bonding in unknown solids from their properties.
• AQA GCSE Chemistry 4.2.2: how bonding and structure are related to the properties of substances. This covers ionic compounds, small molecules, giant covalent structures and metals.

Simulic is not affiliated with or endorsed by the College Board or AQA.

Before the lab (5 min)

Ask students to commit to a prediction:

"Table salt and table sugar both dissolve in water. You dip a lamp-and-battery circuit into each solution. Which solution makes the lamp light?"

Many students say "both, because both dissolve". Keep the votes for later.

Method in the simulation

Part A: practice with known substances

1. Set Mode to Known substances. Choose NaCl and sucrose in turn, set Test to Conductivity: solution, then press Dissolve and Dip electrodes. Note which lamp lights. That tests the prediction.
2. Choose NaCl, Test Heating, Heat source Bunsen burner, and press Heat. Then switch to the Electric furnace and heat again. Read the temperature where the graph goes flat.
3. Repeat the heating with tin and with graphite.

Part B: unknowns

4. Set Mode to Unknown substances with 4 samples. With 4 unknowns, each of the four types appears exactly once.
5. For each sample, run all seven tests and record each result with the buttons under the steps. Use the furnace when a sample doesn't melt over the Bunsen burner.
6. Choose a type and a reason for each unknown, then press Check.

Sample	Melting point	Water	Hexane	Solid conducts	Melt conducts	Solution conducts	Hammer
A
B
C
D

Expected results

Readings from the simulation in Known substances mode:

Substance	Heating	Solubility	Conductivity	Hammer
NaCl	No melt with the Bunsen (reaches about 590 °C); flat at 801 °C in the furnace	water only	solid no; melt and solution yes	shatters
Sucrose	melts at 186 °C and turns brown	water only	never	brittle
Paraffin wax	softens over 50–65 °C, no flat section	hexane only (floats on water)	never	soft, squashes
Tin	flat at 232 °C	neither	solid and melt yes	flattens
Graphite	no melt even in the furnace (about 1,080 °C)	neither	solid yes	soft, flakes
SiO₂ (sand)	no melt even in the furnace	neither	never	very hard grains

• The salt solution lights the lamp and the sugar solution does not. Dissolving alone doesn't show that a substance is ionic.
• The melt test needs the furnace for NaCl. Over the Bunsen burner it doesn't melt, and the simulation says the test can't show anything.
• Graphite is the trap: it conducts as a solid, but it doesn't melt and it flakes instead of flattening. So it is giant covalent, not metallic.

Questions for students

1. (Prediction, asked again after the lab) Which solution, salt or sugar, makes the lamp light?
2. Which is a control variable in the solution conductivity test?
3. At what temperature does NaCl melt in the electric furnace?
4. Which type of substance matches a given property table?
5. Explain why NaCl conducts when molten or dissolved but not as a solid.

Answers for teachers: (1) Only the salt solution. (2) The circuit (battery, lamp, electrodes) and the volume of water. (3) 801 °C (accept 796–806). (4) Giant covalent: the table describes graphite. (5) In the solid, the ions are fixed in the lattice and can only vibrate. When molten or dissolved, the ions are free to move and carry the charge.

Common misconceptions

• "It dissolves in water, so it is ionic." Sucrose and urea dissolve but never conduct. Test whether the solution conducts.
• "It conducts as a solid, so it is a metal." Graphite conducts too. Use the hammer test and the melting point as well.
• "Ionic compounds conduct because they contain electrons that move." In a melt or a solution, the ions themselves move. Ionic solids don't conduct at all.

Extension

• Particle pictures: after a correct Check, students switch the particle picture between Solid, Molten and Dissolved in water for NaCl, then explain each lamp result in one sentence.
• Borderline cases: compare KI (melts at 681 °C) with tin (232 °C). Why is a melting point alone not enough to decide the bonding?

FAQ

Do the unknowns change between students?

Yes. Each New samples press picks new substances, so students can't share answers. With 4 unknowns, one of each type always appears, which makes a good check on their reasoning.

Why do some samples need the electric furnace?

The simulation models a Bunsen and crucible reaching about 600 °C. NaCl, KI, CaCl₂ and aluminum melt above that. Students should use the furnace before they record "does not melt".

Is this safe to replace the real practical?

It covers the hazardous steps: molten salts that spit, flammable hexane and decomposing urea. Many teachers still let students test small samples of salt and sugar for solubility and solution conductivity in the lab.

Related simulations and guides

Crystal lattices in 3D – NaCl, diamond, graphite and metals Testing material properties and comparing fuels

For particle models of melting and boiling, see the states of matter lesson plan. For more chemistry activities, see interactive chemistry lesson ideas.