Measurement and the Metric System Experiment 2. Measurement All measurements in the chemistry lab...

Measurement and the Metric System

Experiment 2

Measurement• All measurements in the chemistry lab will be

taken using metric units.

• Always read a measuring device to the maximum number of digits possible.

• Uncertainty – last digit of a measurement is estimated.

• Always include the units with a measurement.

Metric UnitsQuantity Measured Metric Unit

Volume Liters

Temperature Celsius or Kelvin

Mass Grams

Length Meters

Time Seconds

Metric PrefixesMetric Prefix Multiplier

kilo 1,000 base units

centi 1/10th of a base unit

milli 1/1,000th of a base unit

micro 1/1,000,000th of a base unit

pico 1/1,000,000,000th of a base unit

Mega 1,000,000 base units

Giga 1,000,000,000 base units

Measuring Temperature

• Will measure temperature in units of Celsius or Centigrade oC

• Will use units of Celsius or Kelvin for temperature

– To convert Celsius to Kelvin add 273.16 K• 35.5 oC + 273.2 K = 308.7 K• 533.4 K – 273.2 K = 260.2 oC

This thermometer should be read to the nearest 0.1 oC

This thermometer should be read to the nearest 0.01 oC

Measuring Mass

• Mass will generally be measured in units of grams(g), or kilograms (kg).

• If using an electronic balance, always record all digits showing on the balance.

This electronic balance should be read to the nearest 0.001 g.

Quad Beam Balance

This quad beam balance should be read to the nearest 0.001 g.

This is a balance like we use at Grossmont.

Note that the scale is calibrated to the nearest 0.01 g so you should be able to read it to the nearest 0.001 g.

Measuring Volume

• Volume will be measured in liters (L) or milliliters (mL).

• Sometimes measured in cm3. 1 cm3 = 1 mL

• When measuring volumes in a graduated cylinder always measure the volume at the bottom of the meniscus.

This graduated cylinder should be read to the nearest 1 mL.

This graduated cylinder should be read to the nearest 0.1 mL.

This graduated cylinder contains 27.4 or 27.5 mL of liquid.

This graduated cylinder should be read to the nearest 0.01 mL.

• No writeovers– 375.788g

• No obliterations– 639.824g

• No Erasing• Cross out once and

rewrite.– 4.932g– 5.382g

Rules for recording data

• Be sure to write all data in your lab book in black or blue ink when you take the data. Any data recorded on stray pieces of paper will be confiscated!

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Today’s Experiment

• Part 1 – Measuring temperature and mass– Measure temperature of room temperature

water, boiling water, ice water, and salted ice– Use the quad beam balances to measure mass of

beaker and salt.– When measuring out salt, do not try to get exactly

6 g of salt. Anything between 5.5 and 6.5 grams is fine

Use of Bunsen Burner

Not enough oxygen Better

Today’s Experiment

• Part 2 – Volume measurements– Remember to read measurements at bottom of

meniscus– Read 50 or 100 mL graduated cylinder to nearest

0.1 mL– Read 10 mL graduated cylinder to nearest 0.01

mL.

Today’s Experiment

• Part 3 – Calibrating your eye-dropper– Add drops to the 10 mL graduated cylinder to

increase the volume by 1 mL. – Determine the number of drops of water in 1 mL.– Calculate the volume of one drop of water.

Today’s Experiment

• When you have finished gathering data you need to answer the questions at the end of the lab report.

• After completing the lab report complete worksheet #1

• If you finish both of these before the end of the period, turn them in. Otherwise they are due next week in lab.

What is due today?

• Experiment 1 from last week. • Worksheet #1 and Experiment 2 from this

week if you plan to leave more than 15 minutes before the end of class.