EXPERIMENTAL TECHNIQUES

2.1 Measurement**Core**- Name appropriate apparatus for the measurement of time, temperature, mass and volume, including burettes, pipettes and measuring cylinders

** 2.1 Measurement**

For measuring any quantity, we need to use different tools.

In the table below you will find the units and apparatus used to measure different items.

MEASUREMENT |
UNITS |
APPARATUS |

LENTH |
meter, centimeter, millimeter, etc. |
Ruler, meter stick, meter tape |

TIME |
seconds, minutes, hours, years |
Timer, stop watch, etc |

TEMPERATURE |
Degrees Celsius, Kelvin, (Farenheith) |
Thermometer |

MASS |
Kilogram, gram, milligram, tonn |
Balance or Scale |

VOLUME |
dm, ^{3}cm, L, mL^{3} |
Graduated cylinder, Burette, Pipette |

Each time we measure we need to include the uncertainty of the apparatus we are using.

**How to express a measurement including the uncertainty.**

The steps to follow are the same regardless the instrument you are using:

1.Observe what is the value for the smallest division in your instrument represents.

2.Divide this number by 2.

3.This number represents the error you will show in your measurements.

4.Do not forget to include units in these numbers

** ****How to Measure LENGTH**

For measuring length we use a ruler, a meter stick or a meter tape, the way we express the measurement is always the same.

If you use ruler 1, you can tell that the actual value is between 5.1 cm and 6.1 cm

Using ruler 2, the value will be between 5.50 cm and 5.60 cm.

Which ruler you think will give you a more accurate value?

How to measure VOLUME

For measuring Volumes, we use graduated cylinders, burettes or Pippetes. In all of them we follow the same procedure:

- A meniscus is the curve of the surface of the water in a graduated cylinder.
- Water "sticks" to the walls of the graduated cylinder, but only on the sides and not the middle.
- When measuring liquids be sure that your eyes are aligned with the bottom of the meniscus.

**Step by step:**

- When measuring liquids in a burette be sure that your eyes are aligned with the bottom of the meniscus as always.
- Be aware that the scales are inverted in burettes since we measure the liquid we poured into a container.
- look for the value between the lines.
- In this case, the correct measurement on the left with error included should read:
- Volume on the left burette: 3.30 mL ± 0.05 mL.
- Volume on the right burette: 3.90 mL ± 0.05 mL.

**How to Measure MASS using a triple beam balance**

**Step by step:**

**How to measure TEMPERATURE**

(for more information in how to convert between different temperature scales go to: http://www.metric-conversions.org/conversion-calculators.htm

**Step by step:**

**Be careful when you look at the smallest division value.**

*SOME THERMOMETERS HAVE DIVISIONS EVERY 2 DEGREES.*