Laboratory Equipment, Safety and Procedures

Laboratory Equipment, Safety and Procedures Section 2.1 Handling, Measuring, and Storing Liquids

Pre-View 2.1 • Pipette, burette, and syringe – pieces of glassware used to dispense measured amounts of liquids. • Dropper – piece of equipment used to dispense small amounts of liquid (in drops at a time). • Test tube – glassware used for holding, mixing, and storing small amounts of liquids.

Pre-View 2.1 • Petri dish – glassware commonly used to grow and observe bacteria cultures. • Graduated cylinder – glassware used to accurately measure liquid volume in milliliters. • Meniscus – the curve at the surface of a liquid.

Glassware for Measuring and Dispensing Liquids Various kinds of glassware are used for storing, measuring, and handling liquids, but only a few are used for measurement. • When accurate measurements are needed for liquid volume, scientists use glassware that are marked with graduations.

Graduated Cylinder • A graduated cylinder is used to accurately measure the volume of liquids. • Most common measurement for volume is milliliters, abbreviated mL.

Graduated Cylinder – Meniscus • When measuring liquid in a graduated cylinder, you read the amount of liquid from the center of the meniscus. • The meniscus is the curve at the surface of the liquid • The meniscus of most liquids curves down, but the meniscus of a few, such as mercury, curves up.

Graduated Cylinder – Meniscus

Pipette, Burette • For very small liquid measurements, you can use… • A pipette burette

Syringe • or syringe • These pieces of equipment are also used for dispensing liquids in measured amounts.

Dropper • Droppers are used sometimes for dispensing and measuring small amounts of liquids, • must be used carefully to ensure that the drops are the same size. • As a general rule of thumb, 20 drops equal 1 mL, but this method of dispensing liquids is not as accurate as using a pipette, a burette, or a syringe.

Glassware for Storage, Handling, and Observations • Not all glassware is used for measuring and dispensing liquids. • Some types are used for holding, mixing or storing liquid.

Glassware for Storage, Handling, and Observations • For small amounts of liquids, test tubes can be used for mixing and handling. • Some have caps that allow them to be used for storage as well.

Glassware for Storage, Handling, and Observations • Beakers and Erlenmeyer flasks are commonly used for storing and mixing liquids • Some have measurement markings, but these containers do notgive accurate measurements. • A 250 mL beaker or Erlenmeyer flask will hold at least 250 milliliters of liquid, but you wouldn’t use the beaker or flask to accurately measure 250 mL

Glassware for Storage, Handling, and Observations Beaker Erlenmeyer Flask

Glassware for Storage, Handling, and Observations • A petri dish has several uses. • It is commonly filled with an agar and nutrient solution and then used to grow and observe bacteria cultures. • It can also be used by itself to observe seed germination or small animal behaviors

Laboratory Equipment, Safety and Procedures