Numbers in Science Chemists deal with very large numbers… (Do you recognize this number?)

Examples of Scientific Notation  Given: 289,800,000  Use: (moved 8 places)  Answer: x 10 8  Given:  Use: 5.67 (moved 4 places)  Answer: 5.67 x 10 -4

Example  Given: x 10 6  Answer: 5,093,000 (moved 6 places to the right)  Given: x  Answer: (moved 4 places to the left)

Practice problems  12300=  2.5x10 3 =  1.0x10 -6 =  2.05x10 -3 = 1.23 x ,

Calculations  (4x10 2 )(2x10 3 )=  (4x10 2 )/(2x10 -4 )= 8 x x 10 6

Do you and your calculator have a communication problem?  Solve the problem below using your calculator. 3.0x10 5 = 3.0x10 5 = 1.5x10 2 * 2.0x10 3 1

Measurements in Science  Observations in science should be quantified whenever possible. For this reason, scientists (you) must master the tools used for measuring and the units that are used to express them.

The Importance of Units  Numbers are used in science for quantifying measurements.  However, all numbers must be followed by a unit!!  Naked numbers have no meaning in science! Thus will never receive full credit!

General rules for measurement  All units will be metric. Memorize the units for: Length = meter (m) Length = meter (m) mass = gram (g) mass = gram (g) volume = liter (L) volume = liter (L) ***Important Note!! 1 mL = 1 cm 3

Metric Prefixes

Learning Check Select the unit you would use to measure 1. Your height a) millimeters b) meters c) kilometers 2. Your mass a) milligrams b) grams c) kilograms 3. The distance between two cities a) millimetersb) meters c) kilometers 4. The width of an artery a) millimetersb) meters c) kilometers

Practice 1 kg = g1 m = cm 1 km = m1 L = mL 1 cm = m1 cm = mm 1 mL = L

Units of Length  ? kilometer (km) = 500 meters (m)  2.5 meter (m) = ? centimeters (cm)  1 centimeter (cm) = ? millimeter (mm)  1 nanometer (nm) = 1.0 x 10 ? meter O—H distance = 9.4 x m 9.4 x cm nm O—H distance = 9.4 x m 9.4 x cm nm

The next several slides you will solve on your white board. Write out all conversion factors as ratios showing unit cancellations. When done hold it up for me to evaluate.

What is the volume (in liters) of a 500mL water- bottle?

A rattlesnake is 2.44 m long. How long is the snake in inches?

How fast in mi/hr is 22m/s?

The speed of sound is about 343m/s. If you hear thunder 3.0 seconds after seeing lightning, how far is the storm from you (in miles)

PROBLEM: Mercury (Hg) has a density of 13.6 g/cm 3. What is the mass of 65 mL of Hg in grams? In pounds?