Science AHSGE

Standard I-1, part 2- Appropriate Laboratory Materials

MeasurementMeasurementUniversal system of measurement

Systeme International (SI) or Metric SystemBased on units of ten

King Hendry Died By Drinking Chocolate MilkKilo- 1000s (k)Hecto- 100s (h)Deka- 10s (Da, Dk)BaseDeci- 10ths (d)Centi- 100ths (c)Milli- 1000ths (m)

Base unitsVolume, space- liters,cm3

Mass/weight- GramsDistance, height, width, length- Meters

Measurement Measurement

Accuracy refers to the agreement between a measurement and the true or correct value.

Precision refers to the repeatability of measurement.

Error refers to the disagreement between a measurement and the true or accepted value.

GlasswareGlassware

1. Do not use glassware that is broken, chipped or cracked.2. Always use tongs or a heat-resistant glove to heat

glassware. a. Point test tube away from yourself and others when

heating. b. Allow to cool before storing.

3. If a glassware breaks, do not touch with bare hands. Place in special broken glass container.

Glassware Glassware Graduated cylinder-piece of

laboratory glassware used to accurately measure out volumes of chemicals for use in reactions.

Generally more accurate and precise for this purpose than flasks.

Read from bottom of meniscus

Fluid displacement- Determine the volume of an irregular solid by placing in a graduated cylinder with a known amount of fluid and measuring the difference

Glassware Glassware

Beaker- Simple container for liquids, very commonly used in laboratories.

Generally cylindrical in shape, with a flat bottom

Do not use to measure volume of a liquid.

Use for holding and pouring liquids.

Glassware Glassware Burette (also buret)- Vertical

cylindrical piece of laboratory glassware with a volumetric graduation on its full length and a precision tap, or stopcock, on the bottom.

Used to dispense known amounts of a liquid reagent in experiments for which such precision is necessary, such as a titration of an acid experiment.

Burettes are extremely precise: class A burettes are accurate to ±0.05 mL.

Glassware Glassware Flask- Wider vessel "body" and one

(or sometimes more) narrower tubular sections at the top called necks which have an opening at the top.

Flasks can be used for making solutions or for holding, containing, collecting, or sometimes volumetrically measuring chemicals, samples, solutions, etc. for chemical reactions

Other processes such as mixing, heating, cooling, dissolving, precipitation, boiling (as in distillation), or analysis.

Glassware Glassware Pipette (also called a pipet,

pipettor or chemical dropper)- Instrument used to transport a measured volume of liquid.

Works by creating a vacuum above the liquid-holding chamber and selectively releasing this vacuum to draw up and dispense liquid.

May have a bulb for suction.

Glassware Glassware Petri dish- Shallow glass or plastic cylindrical dish that biologists use to culture cells, which can be bacteria, animal, plant, or fungus

Agar is a gelatinous substance chiefly used as a culture medium for microbiological work

GlasswareGlasswareTest tube (culture tube)-

Piece of laboratory glassware composed of a finger-like length of glass tubing, open at the top, with a rounded U-shaped bottom.

Typically used by chemists to retain multiple discrete samples of materials, usually liquids, during chemical procedures and experiments

Designed to allow easy heating of these samples.

Glassware Glassware

Microscope slide- thin sheet of glass used to hold objects for examination under a microscope.

Wet mount- Object to be viewed is prepared, or mounted, in water underneath a cover slip

Mass MeasurementMass Measurement

Balance (also balance scale, beam balance or laboratory balance) is used to measure the mass of an object.

Triple-beam balance – Balance with a pan and three beams with sliding masses called riders

At one end is a pointerIndicates whether the mass on

the pan is equal to the mass on the beams

Mass MeasurementMass Measurement

Spring scales typically measure force due to gravity, which can be measured in units of force such as newtons or pounds-force.

Mass MeasurementMass Measurement

Analytical balance-instrument used to measure mass to a very high degree of precision. The weighing pan(s) of a high accuracy (0.1 mg or better)

Inside a see-through enclosure with doors so dust does not collect and so any air currents in the room do not affect the delicate balance.

Time MeasurementTime Measurement

Stop Watch- does what its name implies

enables hand timinghas millisecond accuracy

and no artificial limit on hours

Distance MeasurementDistance Measurement

Distance is the measurement from one point to another.

How far away something isCan be length, width, height, depth, altitude, etc.Sometimes need to measure before the volume of a

regular solid can be determined: V= L x W x H

Distance MeasurementDistance MeasurementRuler- the instrument

used to rule lines and the calibrated instrument used for determining measurement

Distance MeasurementDistance MeasurementA tape measure or

measuring tape is a ribbon of cloth, plastic, or metal with linear-measure markings, often in both imperial and metric units.

A meter stick measures up to 40 inches (3.281 feet)

A yard stick measures up to 36 inches (3 feet)

Optical InstrumentsOptical Instruments

A microscope -instrument for viewing objects that are too small to be seen by the naked or unaided eye.

optical instrument containing one or more lenses that produce an enlarged image of an object placed in the focal plane of the lens(es).

Optical InstrumentOptical Instrument

Simple Microscope- Microscope with only one lens

Compound Light microscope- Microscope with more than one lens which uses light to transmit image to your eye

Optical InstrumentOptical Instrument

Electron microscope- uses electrons to illuminate and create an image of a specimen

Transmission electron microscopy (TEM) involves a high voltage electron beam emitted by a cathode, usually a tungsten filament, and focused by electrostatic and electromagnetic lenses

Scanning Electron Microscope (SEM) produces images by detecting low energy secondary electrons which are emitted from the surface of the specimen due to excitation by the primary electron beam

Optical InstrumentOptical Instrument

Reflection Electron Microscope (REM) involves electron beams incident on a surface, but instead of using the transmission (TEM) or secondary electrons (SEM), the reflected beam is detected

Optical InstrumentOptical Instrument

Telescope- an instrument designed for the observation of remote objects and the collection of electromagnetic radiation

Optical InstrumentOptical Instrument

Magnifying glass- (Hand lens) a convex lens which is used to produce a magnified image of an object