In this course practical, students test the conductivity the covalent and also ionic building materials in solid and molten states


This experiment permits students come distinguish in between electrolytes and non-electrolytes, and to verify the covalent substances never conduct electrical energy even once liquefied, conversely, ionic link conduct as soon as molten.

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The practical works well as a course experiment, through students working in groups of 2 to three. There will certainly not it is in time to investigate every the substances, so each group could be assigned three or four of these, and the results pooled in ~ the end.

Equipment

Apparatus

Eye protectionCarbon (graphite) electrodes, fitted in a holder (see note 1 below)Bunsen burnerTripodPipeclay triangleHeat resistant matClamp and also standSmall piece of emery paperConnecting leads and crocodile clipsDC strength pack, 6 VLight pear in holder, 6 V (see keep in mind 2 below)

Apparatus notes

The carbon electrodes should be resolved in some sort of assistance – such together a polythene holder or huge rubber bung – so the there is no possibility of the electrodes being permitted to short-circuit. The electrodes need to be solved in such a means as come fit within the crucible supplied.A light pear has more visual impact, yet an ammeter can be offered instead.

Chemicals

Small piece of lead (TOXIC), copper and perhaps other metalsCrucibles comprise samples of:Phenylsalicylate (salol) (IRRITANT, DANGEROUS because that THE ENVIRONMENT)PolytheneWaxSugarZinc chloride (CORROSIVE, DANGEROUS for THE ENVIRONMENT)Potassium iodideSulfur (optional)

Health, safety and technical notes

Wear eye defense throughout.Lead, Pb(s), (TOXIC) – check out CLEAPSS Hazcard HC056.Copper, Cu(s) – watch CLEAPSSHazcard HC026.Phenylsalicylate (salol), C6 H4 (OH)COOC6 H5 (s), (IRRITANT, DANGROUS because that THE ENVIRONMENT) – check out CLEAPSSHazcard HC052.Wax – view CLEAPSSHazcard HC045b.Sugar (sucrose), C12 H22 O11 (s) – view CLEAPSSHazcard HC040c.Zinc chloride, ZnCl2 (s) (CORROSIVE, DANGEROUS for THE ENVIRONMENT) – see CLEAPSSHazcard HC108a.Potassium iodide, KI(s) - view CLEAPSSHazcard HC047b.Sulfur, S8 (s) – check out CLEAPSSHazcard HC096A. Sulfur is a non-metallic element and is a great substance come have contained in the list. But there is a solid likelihood the it catching fire, with sulfur dioxide, SO2 (g), (TOXIC), given off. Sulfur fires are hard to extinguish. If the happens, covering the vessel with a damp cloth and leave in place until cool. If there is time, sulfur deserve to be done together a teacher demonstration. Warmth a little sample that ‘flowers of sulfur’ very, very slowly. Sulfur is a very poor conductor that heat, and localised heating is most likely to reason it to start burning!You need to use a fume cupboard.

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Part 1

Set increase the circuit as displayed in the diagram, at this stage execute not include the crucible or bunsen burner fire (these are for later).
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Source: Royal culture of Chemistry

The apparatus required for trial and error the conductivity of various substances as soon as solid and molten


Select one of the metals, and also by holding the electrodes in call with it, find out whether or no it conducts electrical energy then switch the existing off.Note down the outcomes using the college student sheetavailable through this resource (see download web links below) and also repeat this experiment with each steel available.Select among the solids contained in a crucible. Lower the electrodes so that they are well immersed in the solid, and then clamp the electrodes in position.Switch on the current and also find out whether the heavy conducts power or not, then switch the existing off again.Set the crucible end a Bunsen burner ~ above a pipeclay triangle and also tripod, and clamp the electrodes in position over the crucible. Gently warmth the sample till it simply melts, and also then revolve off the Bunsen flame. If vital lower the electrodes right into the molten substance, before clamping them again.Switch on the current again. Go the molten problem conduct electrical energy now? switch the existing off again.Write up all your observations.Raise the electrodes from the crucible, and enable them come cool.Clean the electrodes through emery paper.

Part 2

Repeat procaramuseum.orgres 4 come 10 through some or all of the various other solids.

Part 3

Pool your outcomes with other teams so the your table is complete.

Teaching notes

The covalent solids only must be heated because that a quick time for melt to take it place. Under no circumstances must heating be prolonged, otherwise the substances may decompose and/or burn. The students have to be warned about what to perform if this happensegcover v a wet cloth. The experiments need to be excellent in a well-ventilated laboratory.

It might be helpful to make reservation a crucible for each of the powdered compounds, while having one or 2 others that deserve to be heated. Once a solid has actually been liquefied and allowed to cool, the solidified lump is frequently hard to break up or powder in the crucible.

Zinc chloride melts at around 285 °C, so heating needs to be fairly lengthy in comparison v the covalent solids. The will, however, create chlorine (TOXIC) so heating must stopas quickly as conductivity is detected. Potassium iodide melts at about 675 °C, for this reason very strong and an extensive heating is needed here.

Student questions

What perform you conclude about the electrical conductivity the metals?Do all of the hard compounds conduct electricity?Do any type of of the molten compounds conduct electricity. If so, i m sorry ones?Why carry out some substances command only as soon as they have actually been liquefied?Can you currently classify all the compounds together being one of two people ionic or covalent?

Answers

All the steels conduct electricity well. You should explain this conductivity in regards to the ‘free’ electrons in ~ a metallic structure.No, nobody of them.Yes, zinc chloride and also potassium iodide.Some substances are ionic, but electrical conduction is only possible when the ion are complimentary and mobile. This happens once the solid has actually been melted.Phenylsalicylate, polythene, wax and sugar room covalent. Zinc chloride and also potassium iodide room ionic.

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Additional information

This is a resource from thePractical Chemistry project, occurred by the Nuffield structure and the Royal society of Chemistry. This arsenal of end 200 practical tasks demonstrates a wide selection of chemical concepts and processes. Each task contains substantial information because that teachers and also technicians, including full technical notes and step-by-step procaramuseum.orgres. Valuable Chemistry activities accompanyPractical Physics andPractical Biology.