Chapter 13: Practical Physics

What are common working safety precautions?

You need to be able to do the following:
- Handle materials and equipment safely.
- Follow instructions carefully.
- Change how you carry out each step of an equipment, depending
on what happened the time before.

What safety precaution you need to take with bunsen burners?

Following:
- If a bunsen burner is alight, but not in use, always leave it on the
yellow flame setting so that the flame can be seen.
- Make sure that bunsen and tripods have a heatproof mat
underneath.
- Give a hot tripod plenty of time to cool down before attempting to
move it.
- Don't attempt to move a tripod when there is a beaker resting on it.

What safety precaution you need to take with glass thermometers?

Following:
- Don't put glass thermometers where they can roll off the bench.
- Keep glass thermometers away from bunsen flames.
- Mercury, used in some thermometers, is toxic. If a thermometer
breaks and mercury runs out, don't handle it: ask for help from
your lab assistant/technician or teacher.

What safety precaution you need to take with glass tubing?

Following:
- Never attempt to push glass tubing (or glass thermometers)
through a hole in a bung. The laboratory technician has a special
tool for doing this.
- Always handle hot glass tubing with tongs. Rest it on a heatproof
mat; don't put it straight on the bench.
- Hot glass tubing can stay hot for a long time. Give it plenty of time
to cool down before you attempt to pick it up.

What safety precautions you need to take with safe support?

- When clamping a test-tube, don't overtighten the clamp. And make
sure that the clamp has soft pads to touch against the glass. This
also applies when clamping a glass thermometer.
- In experiments where you have to suspend a load, make sure that
the supporting clamp stand is stable enough to take the heaviest
load you will be using. You may need to weigh it down for this, as
shown in the diagram on the left.

What safety precautions you need to take with electricity?

- Before making any changes to the wiring in your circuits, always
switch off the power or disconnect the battery.
- Never make a direct connection across the terminals of a battery. - - Don't put wires or tools where they might connect across the
terminals.
- If a mains appliance is faulty, switch off the power and pull out the
plug. Don't change the fuse. Ask the laboratory technician to deal
with the fault.

What safety precautions you need to take with light?

- Don't look directly into a laser beam or other source of bright light. - Don't stand where laser light might be reflected into your eyes.
- If you need to study the Sun's image, project it onto a card. Never
look through a telescope or binoculars pointing straight at the Sun
-even if there is a filter in front.

What safety precautions you need to take with radioactive sources?

- The radioactive sources used in school laboratories should always
be sealed.
- Radioactive sources should be kept well away from the body, and
never placed where they are pointing at people.

What safety precautions you need to take with fire?

- Don't heat flammable liquids (e.g. methylated spirits) over a
bunsen. If heating is required, a water bath should be used - with
hot water heated well away from the experiment.
- Don't throw water on burning liquids (e.g. methylated spirits).
Smother the fire with a fire blanket or use a carbon dioxide
extinguisher.
- Don't throw water on electrical fires. Switch off the supply and use
a carbon dioxide extinguisher.

How to answer planning and preparing questions? Give steps.

1. Presenting the problem
2. Making a prediction
3. Dealing with variables
4. Final preparations

How to read thermometer correctly?

To measure the temperature of a liquid: keep the liquid well stirred, give the thermometer time to reach the temperature, and keep the lamp in the liquid while you take the reading.

How to read measuring ruler correctly?

Using a ruler: be sure that the scale is right alongside the point you are trying to measure.

How to measure liquid level on a cylinder correctly?

Measuring a liquid level on a scale: look at the level of the liquid's flat surface, not its curved meniscus.

How to draw a graph?

1. Choose axis; where to put which value.
2. Choose suitable scale.
3. Label axis.
4. Draw line of best fit.