# Ch 1 Introducing Science (II)

F.1 Integrated Science · 1.3 The Science Laboratory · 1.4 Laboratory Apparatus and Basic Laboratory Skills · Lesson 2

Lab safety, hazard labels, the fire triangle, common apparatus, the Bunsen burner, and how to measure properly.

## Figure

Left: alcohol is flammable, so it is heated in a water bath, never directly over the flame. Right: the non-luminous flame: B, just above the inner cone, is hottest; C, inside it, is coolest.

## Key points

- **Lab rules**: teacher's permission to enter or experiment; no eating or drinking; goggles when heating or mixing; tie up long hair; report accidents at once; never point a test tube at anyone.
- **Hazard warning labels ／ 危險警告標籤**: harmful, irritant, corrosive (painful burns), flammable, toxic, explosive (when heated or shaken).
- **First aid**: cut → clean and sterilize; burn or chemical on skin → running water; chemical in eye → eye wash bottle; fire → sand, fire blanket or extinguisher.
- **Fire triangle ／ 火三角** = fuel + oxygen + high temperature. Remove any one side and the fire goes out: turning off the gas removes the fuel, a blanket removes the oxygen.
- **Apparatus**: dropper for a little liquid, spatula for a little solid; measuring cylinder for volume; tripod and wire gauze support heating; heat-proof mat protects the bench.
- A **sectional diagram ／ 剖面圖** is a simple line drawing of a section cut through the apparatus. Always **label** it.
- **Bunsen burner**: close the air hole **before** lighting; hand below the top of the chimney; open the air hole **slowly** to adjust, never fully; gas tap off right after use.
- **Striking back ／ 回火**: too much air enters the air hole and the gas burns inside the burner (green flame at the jet, loud noise). Turn off the gas tap at once.
- **Measuring**: temperature in °C; length with a rule; volume in cm³ or mL at the bottom of the **meniscus ／ 彎月面**; mass in kg or g on a balance; repeat and average to reduce error.

## Must know

| | Luminous flame | Non-luminous flame |
|---|---|---|
| **Air hole** | closed | open |
| **Colour** | yellow | blue |
| **Shape** | wavy, irregular | steady, regular, with an inner cone |
| **Noise** | quiet | noisy |
| **Temperature** | lower | higher |
| **Use** | safety flame when not heating (easy to see) | heating |

Reading a scale: thermometer with eyes level with the liquid; ruler straight from above; measuring cylinder on a flat surface, eyes level with the bottom of the meniscus; electronic balance re-zeroed (tare) with the empty container on the pan first.

## Common mistakes

- ✗ Heating with the yellow flame. ✓ Heat with the **blue non-luminous** flame. The yellow luminous flame is the safety flame for when you are not heating.
- ✗ Reading the top of the water in a measuring cylinder. ✓ Read the **bottom** of the meniscus, eyes at the same level. Only mercury curves upwards and is read at the top.
- ✗ Opening the air hole, then lighting the burner. ✓ **Close** the air hole before lighting, then open it slowly. An open hole lets the gas strike back.
- ✗ "The inner cone is the hottest part." ✓ The inner cone (C, ~300 °C) holds unburnt gas and is the **coolest**. The hottest point B (~1500 °C) is just above it.
- ✗ Striking back? Close the air hole. ✓ **Turn off the gas tap** immediately. The gas is burning inside the burner.

## Quick check

1. Name the three sides of the fire triangle. Which side does turning off a gas stove remove?
2. Before lighting a Bunsen burner, should the air hole be open or closed? Why?
3. Which Bunsen flame is used for heating, and what colour is it?
4. A drop of chemical splashes into your eye. What should you do?
5. How do you take the reading of water in a measuring cylinder?

## Answers

1. Fuel, oxygen and a high temperature. Turning off the gas removes the fuel.
2. Closed, to prevent striking back.
3. The non-luminous flame, which is blue.
4. Wash the eye with distilled water from an eye wash bottle.
5. Stand the cylinder on a flat surface and put your eyes level with the bottom of the meniscus.

## Did you know?

The Bunsen burner was built in 1855 for Robert Bunsen by his technician Peter Desaga, and its design has hardly changed since.