Experimental Techniques

Learn it by playing

Answer these questions to earn energy, then fish and explore. No account needed.

For teachers: ready-to-use lesson slides, revision notes, diagrams for Experimental Techniques (Chemistry, CIE) — use them in your lesson, or run the topic as a live class game.

Notes

Apparatus for Measurements

**Time** is measured using a **stopwatch** or **stopclock**, accurate to 1 or 2 decimal places; units are seconds or minutes.
**Temperature** is measured with a **thermometer** (precision ±0.5 °C) or **digital temperature probe** (reads to 0.1 °C).
**Mass** is measured using a **digital balance** (reads to 2 decimal places); always **tare** (zero) before use.
**Volume of liquid** is measured with **burettes** (most accurate for variable volumes, 0–50 cm³), **volumetric pipettes** (most accurate for fixed volumes, e.g. 25 cm³), or **measuring cylinders** (for approximate volumes).
**Volume of gas** is measured using a **gas syringe** (more precise) or **downward displacement of water** (not for soluble gases).
Read the **bottom of the meniscus** for accurate liquid volume readings; burette scale reads 0.00 cm³ at the top.

Solutions Terminology

**Solvent**: the liquid in which a solute dissolves (e.g., water in seawater).
**Solute**: the substance that dissolves (e.g., salt in seawater).
**Solution**: the mixture formed when a solute dissolves in a solvent (e.g., seawater).
**Saturated solution**: contains the maximum concentration of solute at a given temperature.
**Soluble**: a substance that will dissolve (e.g., salt in water).
**Insoluble**: a substance that will not dissolve (e.g., sand in water).
**Filtrate**: the liquid that passes through a filter (e.g., fresh coffee in a cup).
**Residue**: the substance left after filtration, evaporation, or distillation (e.g., coffee grounds).

Acid-Base Titrations: Purpose & Apparatus

Titrations determine the **concentration** of an acid or alkali by neutralisation.
They can also be used to **prepare salts**.
Key apparatus: **25 cm³ volumetric pipette**, **pipette filler**, **50 cm³ burette**, **250 cm³ conical flask**, **small funnel**, **white tile**, **clamp stand**.
A **suitable indicator** (e.g., methyl orange or phenolphthalein) is used to show the endpoint.

Titration Method

1. Use a **pipette** to transfer exactly 25 cm³ of alkali into a conical flask.
2. Fill the **burette** with acid using a funnel; run a little through the tap to remove air bubbles.
3. Record the **initial burette reading** to the nearest 0.05 cm³.
4. Place the flask on a **white tile**; add a few drops of **indicator**.
5. Perform a **rough titration** by adding acid in 1–3 cm³ portions while swirling.
6. Near the endpoint, add acid **drop by drop** until a **sharp colour change** occurs.
7. Record the **final burette reading**; calculate the **titre** (volume added).
8. Repeat until **two concordant results** (within 0.1 cm³) are obtained.

Common Indicators

**Methyl orange**: red in acid, yellow in alkali, orange at neutral.
**Phenolphthalein**: colourless in acid, pink in alkali, colourless at neutral.
**Litmus**: red in acid, blue in alkali, purple at neutral (not suitable for titrations due to gradual change).
**Thymolphthalein**: colourless in acid, blue in alkali.

Common Titration Errors

**Not removing the funnel** from the burette – can cause extra liquid to drip in, giving false high readings.
**Not filling the jet space** (the part below the tap) – leads to inaccurate volume measurements.
**Reading the burette incorrectly** – always read from the **bottom of the meniscus**; scale is 0.0 cm³ at top.
**Using a wide-range indicator** (e.g., litmus) – does not give a sharp colour change at the endpoint.

Advantages & Disadvantages of Apparatus

**Temperature probe**: more precise, easy to automate, but can be corroded and expensive.
**Volumetric pipette**: accurate fixed volume, but harder to use and only one volume.
**Gas syringe**: easy to set up, keeps gas dry, but can stick, limited volume, fragile.
**Microscale experiments**: less wasteful, safer, but hard to observe and product loss in purification.

Planning an Experiment

Choose apparatus suitable for the required **accuracy** and **volume**.
Ensure the method allows for **repeat readings** and **concordant results**.
Consider **safety**, **waste**, and **time** constraints.
Check that the **range** of measurements is appropriate for the investigation.

Particle arrangement in solid, liquid, and gas states.

Practice questions

Free preview — 8 of 40 questions. Sign up to see them all.

1.Which piece of apparatus is most accurate for measuring a variable volume of liquid between 0 cm³ and 50 cm³?
Easy
- ABurette
- BMeasuring cylinder
- CVolumetric pipette
- DBeaker
2.Which term describes the liquid in which a solute dissolves?
Easy
- ASolvent
- BSolute
- CSolution
- DFiltrate
3.What is the substance that remains on the filter paper after filtration called?
Easy
- AResidue
- BFiltrate
- CSolute
- DSolution
4.Which indicator is suitable for an acid-base titration?
Easy
- AMethyl orange
- BLitmus solution
- CUniversal indicator
- DRed litmus paper
5.A student needs to measure exactly 25.0 cm³ of sodium hydroxide for a titration. Which apparatus is most appropriate?
Medium
- AVolumetric pipette
- BMeasuring cylinder
- CBurette
- DBeaker
6.Which of the following is a correct step in performing a titration?
Medium
- AAdd indicator before measuring the alkali
- BFill the burette with the solution to be added
- CRecord the final burette reading before the endpoint
- DUse a beaker to measure the alkali
7.A student investigates the rate of reaction between marble chips and hydrochloric acid by measuring the volume of carbon dioxide produced. Which equipment is essential?
Medium
- AGas syringe, conical flask, bung, delivery tube
- BGas syringe, cotton wool, bung, delivery tube
- CGas syringe, beaker, bung, balance
- DBalloon, conical flask, stopper, balance
8.What is the colour of methyl orange in an alkaline solution?
Medium
- AYellow
- BRed
- COrange
- DPink

Slides

Apparatus for Measuring Volume

Burettes measure variable volumes accurately (0–50 cm³), used in titrations.
Volumetric pipettes measure a fixed volume accurately (e.g. 25 cm³).
Measuring cylinders give approximate volumes; they are less accurate.

Which piece of apparatus is most accurate for measuring a variable volume of liquid?

Measuring cylinder
Burette
Volumetric pipette
Beaker

Measuring Gas Volumes

Gas syringes measure gas volume precisely and keep the gas dry.
Downward displacement of water uses an inverted measuring cylinder; it does not work for soluble gases.
A gas syringe is more accurate than downward displacement.

A ____ is the most accurate way to measure a variable volume of liquid, while a ____ measures a fixed volume accurately.

Measuring Time, Temperature and Mass

Time is measured with a stopwatch or stopclock; units are seconds or minutes.
Temperature is measured with a thermometer (precision ±0.5°C) or digital probe (precision ±0.1°C).
Mass is measured with a digital balance (to 2 decimal places); always tare before use.

A stopwatch shows 1:30. What is the correct time in minutes?

1.30 minutes
1.5 minutes
90 minutes
1.3 minutes

Solutions Terminology

Solvent: the liquid that dissolves a solute (e.g. water).
Solute: the substance that dissolves (e.g. salt).
Solution: the mixture of solute and solvent.
Filtrate: liquid that passes through a filter; Residue: solid left behind.

Which of these are correct definitions?

A solute is the substance that dissolves.
The filtrate is the solid left on the filter paper.
A saturated solution contains the maximum solute at a given temperature.

Acid-Base Titrations

Titrations determine the concentration of an acid or alkali by neutralisation.
Apparatus: burette, volumetric pipette, conical flask, white tile, indicator.
The endpoint is shown by a sharp colour change of the indicator.

What is the correct order for a titration?

Add indicator → transfer alkali → fill burette → record initial reading → titrate
Transfer alkali → add indicator → fill burette → record initial reading → titrate
Fill burette → record initial reading → transfer alkali → add indicator → titrate
Transfer alkali → fill burette → add indicator → record initial reading → titrate

Titration Method Details

Use a pipette filler to draw liquid into the volumetric pipette.
Fill the burette using a funnel; run a little through the tap to remove air bubbles.
Record burette readings to the nearest 0.05 cm³.
Repeat until two concordant results (within 0.1 cm³) are obtained.

The burette reading should be taken from the ____ of the meniscus. The scale reads from ____ at the top to 50 cm³ at the bottom.

Common Titration Errors

Not removing the funnel from the burette can cause false high readings.
Not filling the jet space (below the tap) leads to false readings.
Reading the burette incorrectly (e.g. from top of meniscus).

Why is it important to fill the jet space of a burette before starting a titration?

To make the burette easier to read
To avoid false readings because the scale does not include this volume
To prevent the indicator from changing colour too early
To ensure the acid is at the correct concentration

Indicators for Titrations

Methyl orange: red in acid, yellow in alkali, orange at endpoint.
Phenolphthalein: colourless in acid, pink in alkali.
Litmus is not suitable because it does not give a sharp colour change.

Which indicators are suitable for titrations?

Methyl orange
Litmus solution
Phenolphthalein

Advantages and Disadvantages of Apparatus

Temperature probes: more precise but can be corroded by reagents.
Volumetric pipettes: accurate fixed volume but only one volume.
Gas syringes: easy set-up, keeps gas dry, but can stick and are fragile.
Microscale experiments: less wasteful and safer, but hard to see and product loss.

Which is a disadvantage of using a gas syringe?

It is not accurate
It can stick and is fragile
It cannot measure gas volume
It requires water

Unlock all 40 questions, slides & more

Create a free account to see every question, the slides, flashcards and revision notes for this topic.

Past papers

Past-paper practice for this topic is coming soon.

🗂️ Coming soon