Quick answer: Ionic bonding is the strong electrostatic attraction between oppositely charged ions, formed when metal atoms transfer electrons to non-metal atoms. This Chemistry 9-10 lab on ionic bonding gives the aim, the equipment, the safety points, a step-by-step method, sample results and 7 analysis questions; the answers are on a separate page and the lab sheet is a free printable PDF.
Which substances carry an electric current, and what does this tell you about their ions? You will test solids and solutions with graphite electrodes, plot current against the mass of sodium chloride dissolved, and explain the pattern.
Level: Chemistry grades 9-10 (GCSE · IGCSE · O Level · Class 9-10) · Curriculum: HS-PS1-3, GCSE C2
Aim
To test which substances conduct electricity as solids and as solutions, and to find how the current depends on the amount of sodium chloride dissolved.
Equipment
- 4.5 V supply (batteries or power pack), leads and a milliammeter
- Two graphite electrodes
- 100 cm³ beakers, distilled water, balance
- Sodium chloride, sugar (sucrose) and a piece of candle wax
- Stirring rod and a dry watch glass
Safety
Keep leads and electrodes dry apart from the tips, and switch off before moving anything. Do not taste any substance. Wipe up spills at once so the floor is not slippery, and wash your hands after the lab.
Method
- Press the electrodes 1 cm apart onto each dry solid (salt crystals, sugar, wax) in turn and note the current.
- Measure 100 cm³ of distilled water into a beaker. Place the electrodes 2 cm apart and 3 cm deep, and record the current.
- Dissolve 1.0 g of sodium chloride in the water, stir, and record the current. Add further 1.0 g portions up to 5.0 g in total, recording the current each time.
- Repeat step 2 with 5.0 g of sugar in 100 cm³ of fresh distilled water.
Results
| Test | Current / mA |
|---|---|
| Solid sodium chloride | 0 |
| Solid sugar | 0 |
| Candle wax | 0 |
| Distilled water | 0.3 |
| Sugar solution (5.0 g) | 0.3 |
| Mass of NaCl dissolved / g | 0 | 1.0 | 2.0 | 3.0 | 4.0 | 5.0 |
|---|---|---|---|---|---|---|
| Current / mA | 0.3 | 38 | 72 | 105 | 138 | 168 |
Analysis questions
Question 1 Plot the graph
Plot the current (y-axis) against the mass of sodium chloride dissolved (x-axis). Describe the shape of the graph.Question 2 Explain the trend
Explain why the current increases as more salt dissolves.Question 3 Gradient
Calculate the average increase in current per gram of sodium chloride between 0 and 5.0 g.Question 4 Solids and sugar
Explain why solid sodium chloride does not conduct but its solution does, and why sugar solution does not conduct.Question 5 Interpolate
Use your graph to estimate the current for 3.5 g of sodium chloride.Question 6 Control variables
Name three variables that must be kept constant and explain why.Question 7 Evaluate
The ammeter reads to 1 mA. Calculate the percentage uncertainty in the 38 mA reading and suggest one improvement.
