The shape of the lesson
By the end of the lesson, learners can
- Measuring quantities: Each quantity has its own apparatus.
- Solutions and mixtures: Questions on separation and titration use these terms precisely.
- Time: stopwatch. Temperature: thermometer. Mass: balance.
- Volume: burette (variable), volumetric pipette (fixed), measuring cylinder (rough), gas syringe (gas).
- Solvent dissolves solute to give a solution.
- Residue stays in the filter paper; filtrate passes through.
One picture every idea returns to
Choose apparatus to match the quantity and the precision needed. Time is measured with a stopwatch or stop-clock, temperature with a thermometer, mass with a balance, and volume with a burette (variable volumes, to 0.05 cm3), a volumetric pipette (one fixed volume, very accurately), a measuring cylinder (quick but less precise) or a gas syringe (volumes of gas). A solvent dissolves a solute to make a solution; a saturated solution holds the maximum amount of solute at that temperature. After filtration, the solid left in the filter paper is the residue and the liquid that passes through is the filtrate.
Forty-five minutes, phase by phase
| Time | Phase | What happens in the room | Grouping |
|---|---|---|---|
| 0 to 5 min | Hook: predict | Open with the question in the title, The right tool for every measurement.. Every practical question starts with the same choices: what to measure, which apparatus to use and how precise it needs to be. Put the figure on the board: it is the one picture every idea in the lesson returns to. | Whole class, then pairs |
| 5 to 17 min | Teach and check: Measuring quantities | Each quantity has its own apparatus. | Whole class, then pairs |
| 17 to 30 min | Teach and check: Solutions and mixtures | Questions on separation and titration use these terms precisely. | Frayer Model |
| 30 to 36 min | Check | The four Stage 1 questions from the student lesson, answered on mini whiteboards or by show of fingers. Re-teach the one most get wrong. | Individual, then whole class |
| 36 to 43 min | Plenary | The exam-style questions from Stage 2, one at a time: thirty seconds alone, then a random call. The feedback lines in the key give the examiner's wording. | Individual, random call |
| 43 to 45 min | Exit and homework | Set the worksheet below (6 questions, 15 marks). Learners self-assess against the objectives before they leave. | Individual |
Protect the parts that carry the learning
The sequence carries about fifty minutes of material, so the lab is driven by one student while the class predicts rather than explored freely. Times are a guide.
Protected: the check at 30 minutes. It is the only individual read on whether the key idea landed, and it is not cut.
Cut first if the build overruns: the last check in Solutions and mixtures, never the check or the plenary.
In a 60 minute block: run worksheet questions 1 to 3 in class as a Rally Coach set and model both the hardest worked example and its check live.
Frayer Model
Pairs fill a four-box grid for the key term: definition, characteristics, examples and non-examples. The non-examples box is where the misconceptions surface, so give it the most time.
The full structure, with its variations and the other twelve, is on the cooperative-learning page.
What to head off, and how
| Trap learners fall into | Teaching move that pre-empts it |
|---|---|
| The filtrate is what passes through the paper, the residue is what stays behind: do not swap them. | A measuring cylinder is not suitable for a titration, and a gas collected over water must be only slightly soluble (carbon dioxide and ammonia are better measured with a gas syringe). Always give a volume read from a burette to 2 decimal places, ending in 0 or 5. |
Experimental design and apparatus: worksheet
6 questions, 15 marks. Written in the style of the papers; no past paper question is reproduced.
Name the apparatus used to measure (a) time, (b) temperature, (c) mass and (d) the volume of a gas.
Define the terms solute and saturated solution.
A mixture of chalk and water is filtered. Name the residue and the filtrate.
Explain why a volumetric pipette, not a measuring cylinder, is used to measure 25.0 cm3 of alkali for a titration.
A student measures the temperature rise when magnesium is added to acid in a glass beaker, using a thermometer reading to 1 °C. Suggest two improvements and explain each.
A student collects ammonia over water to measure its volume. Explain why this method is unsuitable and suggest a better one.
Answer key and marking notes
- (a) stopwatch (or stop-clock).
- (b) thermometer.
- (c) electronic balance.
- (d) gas syringe.
- Solute: the substance that is dissolved in a solvent.
- Saturated solution: a solution containing the maximum concentration of solute dissolved in the solvent at a specified temperature.
- Residue: chalk (calcium carbonate), left in the filter paper.
- Filtrate: water, which passes through the paper.
- A volumetric pipette delivers a fixed volume much more accurately.
- Titration results are only as accurate as the volume of alkali used, so the least precise step must be avoided.
- Use a polystyrene cup with a lid instead of a glass beaker.
- This reduces heat lost to the surroundings, so the temperature rise is more accurate.
- Use a thermometer reading to 0.1 or 0.5 °C, giving more precise readings.
- Ammonia is very soluble in water, so most of it dissolves and the measured volume is far too low.
- Collect the gas in a gas syringe instead.
8 multiple-choice questions on this lesson
From the topic question bank. Assign them in the app for a marked score in your gradebook, or run the topic as a class game.
A student needs to measure out exactly 25.0 cm3 of sodium hydroxide solution for a titration. Which apparatus should be used?
- Avolumetric pipette
- Bmeasuring cylinder
- Cbeaker
- Dgas syringe
Which list correctly matches each quantity to the apparatus used to measure it?
- Atime: stopwatch; temperature: thermometer; mass: balance
- Btime: balance; temperature: stopwatch; mass: thermometer
- Ctime: stopwatch; temperature: balance; mass: burette
- Dtime: thermometer; temperature: stopwatch; mass: balance
A mixture of sand and copper(II) sulfate solution is filtered. Which row is correct?
- Aresidue: sand; filtrate: copper(II) sulfate solution
- Bresidue: copper(II) sulfate solution; filtrate: sand
- Cresidue: copper(II) sulfate crystals; filtrate: water
- Dresidue: sand and copper(II) sulfate; filtrate: water
Which statement describes a saturated solution?
- Aa solution containing the maximum concentration of solute that can dissolve at that temperature
- Ba solution in which the solvent has completely evaporated
- Ca solution that contains more solvent than solute
- Da solution that has been filtered to remove all solids
Which burette reading is recorded correctly?
- A18.35 cm3
- B18.3 cm3
- C18.37 cm3
- D18 cm3
The volume of carbon dioxide from marble chips and acid is measured with the apparatus shown. Why is this better than collecting the gas over water in an upturned measuring cylinder?
- Acarbon dioxide dissolves in water, so collecting over water gives a volume that is too low
- Bthe gas syringe makes the reaction go faster
- Ccarbon dioxide is less dense than air, so it would escape from the cylinder
- Da measuring cylinder cannot measure volumes of gas at all
A student heats water in a glass beaker with a spirit burner and records the temperature rise to find the energy released by a fuel. The result is much lower than the data book value. Which change would most improve the accuracy?
- Ause a copper can with a lid and shield the flame from draughts
- Buse a larger volume of fuel in the burner
- Crecord the temperature every second instead of every minute
- Duse a measuring cylinder instead of a balance for the fuel
Which apparatus would give the most precise measurement of the volume of acid needed to neutralise 25.0 cm3 of an alkali?
- Aburette
- B100 cm3 measuring cylinder
- Cvolumetric pipette
- Dgas syringe
Quiz key
A volumetric pipette is calibrated to deliver one fixed volume, such as 25.0 cm3, very accurately, which is what a titration needs. A measuring cylinder is quicker but much less precise. A beaker has only rough markings and is not a measuring instrument. A gas syringe measures volumes of gas, not liquids.
A stopwatch measures time in seconds, a thermometer measures temperature in °C and an electronic balance measures mass in grams. The other lists swap these instruments: a balance cannot time a reaction, a stopwatch cannot read temperature, and a burette measures liquid volume, not mass.
Sand is insoluble, so it stays in the filter paper as the residue. Copper(II) sulfate is dissolved, so the whole solution passes through as the filtrate. Swapping the two terms is the classic error. Filtration does not separate a dissolved solute from its solvent, so no crystals stay in the paper and the filtrate is still blue solution, not pure water.
A saturated solution holds the maximum amount of solute that will dissolve in the solvent at a stated temperature; any more solute stays undissolved. If all the solvent evaporated there would be no solution. Most solutions contain more solvent than solute, so that does not define saturation. Filtering removes insoluble solids but says nothing about how much solute is dissolved.
Burette readings are recorded to the nearest 0.05 cm3, so they have two decimal places ending in 0 or 5, as in 18.35 cm3. 18.3 has only one decimal place, so it does not show the precision of the burette (it should be written 18.30). 18.37 claims more precision than the scale allows. 18 cm3 is far too rough.
Carbon dioxide is fairly soluble in water, so some of it dissolves as it bubbles through and the measured volume is too low. A gas syringe collects all the gas without contact with water. The syringe does not change the rate. Carbon dioxide is denser than air, not less dense. An upturned measuring cylinder full of water can measure a gas volume, which is why this method is used for gases that are only slightly soluble, such as hydrogen.
The main error is heat lost to the surroundings, so a copper can (a good conductor, so heat reaches the water), a lid and a draught shield reduce the losses and raise the measured temperature rise. Burning more fuel does not change the energy per gram. Reading more often does not stop heat loss. The mass of fuel burned is measured with a balance; a measuring cylinder would be less suitable, not more accurate.
A burette delivers a variable volume and is read to 0.05 cm3, so it is the right choice when the volume needed is unknown. A volumetric pipette is very accurate but delivers only one fixed volume, so it is used for the alkali, not to find the volume of acid. A 100 cm3 measuring cylinder is far less precise. A gas syringe measures gases.
Slides for this lesson
A projectable deck for every pack is on the way. Until then, present the student lesson full screen: its sections, figure and lab tabs follow the same order as the plan above.