Exercises: The laboratory: equipment and safety rules

Match each piece of lab equipment with its use:

1. a) Graduated cylinder
2. b) Thermometer
3. c) Balance

1) Measuring the temperature of water.

2) Measuring a volume of liquid fairly accurately.

3) Measuring the mass of a solid.

You need to measure exactly $25\ \text{mL}$ of water for an experiment. The three containers are shown in the figure:

Which piece of equipment would you use: a beaker, a graduated cylinder, or an Erlenmeyer flask? Justify your choice.

What is the Bunsen burner used for in the lab? Write down two safety rules that must always be followed when using it.

The Erlenmeyer flask is wide at the base and narrow at the neck, as shown in the figure.

Explain what advantage this shape has when swirling a mixture.

Before entering the laboratory, the teacher requires everyone to put on a lab coat and, for some labs, safety goggles as well. Explain what each protects against.

In the lab, it is forbidden to taste any substance, even if it looks like water.

1. a) If you need to smell a chemical, how is it done safely?
2. b) Why do you think this rule exists?

You drop a test tube on the floor and it breaks. State two things you should do immediately and one thing you must never do.

On the label of some alcohol you see a pictogram with a flame, and on another chemical, a skull and crossbones. Observe the two pictograms:

1. a) What hazard does each pictogram indicate?
2. b) What precaution would you take with each chemical?

You are going to heat $100\ \text{mL}$ of water and want to record its temperature every minute.

1. a) Make a list of the equipment you need (at least four items).
2. b) Write, in order, the steps you will follow.

At the next desk, Mateo is dipping a cookie into a beaker of water while his lab partner, who has long loose hair, leans over a lit Bunsen burner. Point out the two safety mistakes and write down the rule that corrects each one.

Using the balance, you measure an empty beaker: $50\ \text{g}$. Then you fill it with water and it reads $125\ \text{g}$.

1. a) What mass of water have you poured in?
2. b) Explain why it is necessary to measure the empty beaker first.

A graduated cylinder contains $30\ \text{mL}$ of water and you add $45\ \text{mL}$ more, measured with another graduated cylinder.

1. a) What total volume is there now?
2. b) Explain why a graduated cylinder is used to measure volumes rather than a beaker, even if the beaker has some markings.

You are going to use alcohol, whose label bears the flame pictogram (flammable), and on the adjacent lab table there is a lit Bunsen burner. Write down two specific precautions you must take and explain what the hazard is.

You need to mix water and salt by swirling without splashing. The two containers are shown in the figure:

Which container would you choose: a wide-mouthed beaker or an Erlenmeyer flask? Explain your choice by referring to the shape of each one.

When measuring the temperature of heated water, the thermometer must not touch the bottom of the beaker. Observe the setup in the figure:

1. a) Explain why.
2. b) If the bottom is hotter than the water, would the reading be higher or lower than the actual temperature?

A few drops of an irritant chemical splash onto your lab partner's hand. Write down two actions she should take immediately and one thing she must not do.

Observe this laboratory scene: Olivia is working with loose hair, she has left her sandwich on the bench, the Bunsen burner is lit while unattended, a classmate tastes a liquid "because it looks like lemonade", and there are sheets of paper right next to the flame. Find the five safety mistakes and write down the rule that corrects each one.

You must heat $50\ \text{mL}$ of salty water to $40\ ^\circ\text{C}$ and measure the temperature while it heats up. Write down the complete procedure: the required equipment, the steps in order, and the safety rules you apply at each stage, justifying at least two of them.

Explain the reason for each of these laboratory rules:

1. a) Unused chemicals are never returned to their original container.
2. b) Every container holding a substance must be labeled.
3. c) At the end of the lab, equipment is washed and the lab bench is cleared.

You need to use a chemical with the skull pictogram (toxic) and, in another lab activity, alcohol with the flame pictogram (flammable).

1. a) Write down two specific safety measures for each chemical.
2. b) Explain why the measures are different in each case.

A student spills a small amount of dilute acid on their hand.

1. a) Write down the correct actions in order.
2. b) Explain why home remedies such as toothpaste or oil should not be applied.
3. c) State what information you must give to the teacher.

Before starting a lab activity involving a Bunsen burner, you must prepare the work area. Make a list of at least four things you should do or remove before lighting the flame, and justify each one in a sentence.

You have a graduated cylinder with graduations every $2\ \text{mL}$ and a beaker with graduations every $50\ \text{mL}$, as shown in the figure.

You need to measure $36\ \text{mL}$ of water.

1. a) Which piece of equipment do you choose?
2. b) Justify your choice by considering the error you would make with each one.
3. c) Using this example, explain what it means for an instrument to be "more precise".

A test tube falls to the floor, breaks, and the liquid spills across the floor.

1. a) Describe the complete, step-by-step protocol to act safely: reporting the incident, cordoning off the area, what to use to sweep up the glass, and how to deal with the liquid.
2. b) Justify why glass must not be picked up with your hands.