Safety first
Lab work is fun, but it has real risks. Before you step into a lab, learn these rules:
- Wear a lab coat and safety goggles, and tie back long hair.
- Never touch chemicals with your hands, never put your nose to a container to smell it, and never taste anything. To smell a gas, gently waft a little toward your nose with your hand.
- Never return leftover chemicals to the original bottle or throw them away just anywhere. Use the container your teacher provides.
- No eating or drinking in the lab.
- If acid or base splashes on your skin, rinse it right away with lots of water and tell your teacher.
- If you don’t recognize a chemical or aren’t sure about a step, ask before you start.
Hazard symbols
The symbol on a bottle tells you what the danger is:
| Symbol | Meaning | Examples |
|---|---|---|
| 🔥 Flame | Flammable | Alcohol, gasoline |
| ☠️ Skull and crossbones | Toxic | Cyanides |
| Liquid dripping onto a hand and metal | Corrosive | Concentrated sulfuric acid, sodium hydroxide |
| Flame over a circle | Oxidizer (feeds fire) | Potassium permanganate |
| 💥 Exploding bomb | Explosive | Fireworks powder |
| ❗ Exclamation mark | Irritant or harmful | Concentrated ammonia |
Common lab equipment
Know which equipment can be heated:
- Heat directly: test tubes, evaporating dishes, combustion spoons, crucibles.
- Heat on a wire gauze: beakers, round-bottom flasks, Erlenmeyer flasks (their wide bottoms can crack if heated unevenly).
- Never heat: graduated cylinders, gas jars.
Using an alcohol burner
Many school labs, especially in China, use alcohol burners instead of Bunsen burners. The safety ideas are the same.
- Check it. The wick should be trimmed flat, and the alcohol should fill no more than 2/3 of the burner.
- Light it. Use a match. Never light one burner from another burning one.
- Heat with it. Use the outer part of the flame, which is the hottest.
- Refill it. Put it out first. Never add alcohol to a lit burner.
- Put it out. Cover it with its cap; never blow it out. If spilled alcohol catches fire on the bench, smother it right away with a damp cloth.
- Measure out 8 mL of water
Use a graduated cylinder to measure liquid volume.
- Weigh out 5.2 g of salt
Use a balance to weigh solids, to 0.1 g.
- Add 2 drops of indicator to a test tube
Use a dropper to add small amounts of liquid.
- Heat a small amount of liquid
A test tube can be heated directly.
- Dissolve a larger amount of solid to make a solution
Make solutions in a beaker.
- Guide liquid into the funnel while filtering
A stirring rod guides the liquid while you filter.
- Evaporate salt water to get the salt
Use an evaporating dish to evaporate a solution.
- Blowing out an alcohol burner
It can push the flame inside and ignite the alcohol. Cover it with the cap.
- Wafting a gas toward your nose with your hand
This is the correct way to smell a gas.
- Pouring leftover chemicals back into the bottle
It can contaminate the whole bottle.
- Pointing a heated test tube at a classmate
Liquid can spurt out. Never point a test tube at anyone.
- Wearing goggles during experiments
Goggles protect your eyes and should stay on the whole time.
- Adding alcohol to a lit burner
This can start a fire. Put the burner out first.
- Rinsing acid off your hand right away with lots of water
Plenty of water dilutes and washes away the acid. Then tell your teacher.
Common mistakes
Mistake 1: Heating or mixing solutions in a graduated cylinder. A graduated cylinder is only for measuring volume. Never heat it or use it as a reaction vessel.
Mistake 2: Putting a beaker straight on the flame. A beaker’s wide base heats unevenly and can crack. Put it on a wire gauze.
Mistake 3: Skipping safety because you’re using only a little. Some chemicals are corrosive or toxic even in tiny amounts. Follow the rules every time.
Quick check
Which of these can be heated directly over a flame?
A test tube can be heated directly. A beaker needs a wire gauze, and graduated cylinders and gas jars can't be heated.
Which hazard symbol belongs on a bottle of concentrated sulfuric acid?
Concentrated sulfuric acid is highly corrosive.
Summary
- In the lab: wear goggles, and never touch, sniff directly, or taste chemicals. Put leftovers in the container provided.
- Know the hazard symbols: flammable, toxic, corrosive, oxidizer, explosive, irritant.
- Test tubes and evaporating dishes can be heated directly; beakers and flasks need a wire gauze; graduated cylinders can’t be heated.
- Alcohol burner: light with a match, heat with the outer flame, put out with the cap. Never light one from another or refill while lit.
On to AP (for later)
AP Chemistry has 16 recommended labs, and lab questions often ask you to choose the right equipment, such as why a pipet or volumetric flask is used for a precise volume instead of a beaker. That’s AP Science Practice 2, Question and Method.