Introduction to Chemistry Metric Conversions Scientific Notation

How do we use units to measure things? What unit of measurement would/do we use to measure… Height? Weight? Driving Distance? Price? What if we got more specific… Height of a person? Height of a building? Distance from Charter Oak High School to Disneyland? Distance from your seat to the door? Weight of a person? Weight of an elephant?

How do we measure things in science? Length – meter (m) Mass – gram (g) Volume – liter (L or l) Time – second (s) Temperature – Celsius (C) or Kelvin (K) Amount of substance – Mole (mol)

The Metric System

SI (Système Internationale d’Unités ) Chapter 1 SI (Système Internationale d’Unités )

Common Prefixes Kilo- 1000 Hecto- 100 Deka- 10 Deci- 1/10 Centi- 1/100 Milli- 1/1000

Conversion Factors Used to switch from one unit to another unit Ex 1- Changing meters to centimeters Ex 2- Changing hours to minutes

Writing a conversion factor as a fraction

Using dimensional analysis or unit analysis to convert one unit to another

Metric Conversions **Notice- The 1 always goes next to the larger unit 1 km = 1000 m 1 hm = 100 m 1 Dm = 10 m 10 dm = 1 m 100 cm = 1 m 1000 mm = 1 m Now you write the conversion factors for liters and grams

Examples 1. 700 m to km 2. 3.50 L to mL

Scientific Notation A number is expressed in scientific notation when it is in the form a x 10n where a is between 1 and 10 and n is an integer ****In other words, the decimal must be after the first digit!!!

Write the width of the universe in scientific notation. 210,000,000,000,000,000,000,000 miles Where is the decimal point now? After the last zero. Where would you put the decimal to make this number be between 1 and 10? Between the 2 and the 1

2.10,000,000,000,000,000,000,000. How many decimal places did you move the decimal? 23 When the original number is more than 1, the exponent is positive. The answer in scientific notation is 2.1 x 1023

1) Express 0.0000000902 in scientific notation. Where would the decimal go to make the number be between 1 and 10? 9.02 The decimal was moved how many places? 8 When the original number is less than 1, the exponent is negative. 9.02 x 10-8

Two step unit conversions If you do not have a conversion factor between the given unit and the one you are looking for, you must do two conversions. Example- How many milliliters are in 0.005 kiloliters?

Practice 1) 254 mm =____________km 6) 97.8 mg = _____________kg 2) 0.004 kg = ___________mg 3) 46 cL = _____________ kL 4) 675 km = ____________ cm 5) 0.072 kL = ___________mL 6) 97.8 mg = _____________kg 7) 1.88 ms = ______________ cs 8) 6.48 cm = _____________mm 9) 14.72 kL = ____________ mL 10) 25 mm = ______________cm ** All of the given units and all of the units I asked for have a prefix… that means it is a two step problem! Convert to the base unit first!!!!

More Examples… Ex 2 Ex 3 2750 centigrams to kilograms 0.001 kilometers to millimeters