Section 3: MeasurementChapter 2: Measurement and Problem Solving

Learning ObjectivesPractice measuring according to significant figures.

Measurement What is the volume of

water in the graduated cylinder in mL?

How many sigfigs is this? How many L is this? Express this number in

sci. notation.

Measurement Always take the measurement to one decimal

place past the smallest gradation (tic mark) Graduated cylinders

▪ Beakers/flasks/bottles /etc. are NOT used for measuring! Measure the volume of liquids ONLY with a graduated cylinder

Rulers

When using the electronic balance, record the entire number on the screen

21.75 mL

2.65 cm

3.53 cm

Measurement The bathroom

scale has markings at every 1 lb. Report the reading to the correct number of digits.

MeasurementThe unit system for

science measurements, based on the metric system, is called the International System of Units or SI units.

MeasurementThe standard of length  

The definition of a meter, established by international agreement in 1983, is the distance that light travels in vacuum in 1/299,792,458 s. (The speed of light is 299,792,458 m/s.)

MeasurementThe standard of mass

The kilogram is defined as the mass of a block of metal kept at the International Bureau of Weights and Measures at Sèvres, France. A duplicate is kept at the National Institute of Standards and Technology near Washington, D.C.

MeasurementThe kilogram is a measure of mass, which

is different from weight. The mass of an object is a measure of the

quantity of matter within it.

The weight of an object is a measure of the gravitational pull on that matter.

Consequently, weight depends on gravity while mass does not.

Measurement

The standard of time   The second is defined, using an atomic clock, as the duration of 9,192,631,770 periods of the radiation emitted from a certain transition in a cesium-133 atom.