Scientific Notation Significant Figures Conversion Factors

Bell ringer answer the following in your notebook What is the metric System? Susan conducts an experiment five times and gets a solution concentration of 1.9M, 2.1M, 1.8M, 1.9M, and 2.2M. The known concentration of the solution is 2.0M. Which of the following are true about Susan's results? They are precise, but not accurate. They are accurate, but not precise. They are both accurate and precise. They are neither accurate nor precise.

Metric Measurement Metric System – The standard measurement system used by scientists around the world. Also called the International System of Units, or SI. It is a decimal system, based on the number 10 and multiples of 10.

Uncertainty in Measurement Uncertainty comes from limitations of measuring devices, experimental design, experimenter, and nature’s random behavior. Accuracy – how close a measurement comes to the actual value. Precision – how close measurements are to one another, or how reproducible they are. Not Accurate and Not Precise Accurate but Not Precise Not Accurate but Precise Accurate and Precise

For example 54 000 can be expressed as 5.4 x 104 Scientific Notation For example 54 000 can be expressed as 5.4 x 104 in scientific notation, and the number 0.000 008 765 can be expressed as 8.765 x 10-6.

The base is always between 1 and 9.99 As the preceding examples show, each value expressed in scientific notation has two parts. The base is always between 1 and 9.99 (less than 10)

To write the first factor of the number, move the decimal point to the right or left so there is only one nonzero digit to the left of it. Examples 5467 0.004389

The second part is raised to an exponent of 10. The exponent is determined by counting the number of places the decimal point must be moved. If the decimal point is moved to the left, the exponent is positive. If the decimal point is moved to the right, the exponent is negative.

Examples Express each of the following in scientific notation. 67 000

Examples Express each of the following in standard form. 8.2 x 103 1.5 x 10-6 8200 0.000 001 5

Examples 1.775 x 107 7.065 x 10-5 17 750 000 0.000 070 65

Percent error

Significant Figures Significant figures let other people know just how good the measurement is!

Significant Figures 99,000 2 sig figs 99,000. 5 sig figs 0.0099 Examples: How many significant figures? 99,000 2 sig figs 99,000. 5 sig figs 0.0099 2 sig figs 0.0990 3 sig figs

Do Not Count Sig Figs When Using standardized values Or Molar Mass from the periodic table

Calculating with Significant Figures When you use your measurements in calculations, your answer may only be as exact as your least exact measurement. For addition and subtraction, round to the fewest decimal places. Example: (3 decimals) (1 decimal) (unrounded) (rounded) 50.259 + 17.4 = 67.659 67.7 For multiplication and division, round to the fewest significant figures. Example: (3 sigfigs) (1 sigfig) (unrounded) (rounded) 0.135 x 20 = 2.7 3

Conversion Factors A conversion factor is a ratio derived from the equality between two different units that can be used to convert from one unit to the other! Remember that solving a chemistry problem is like taking a trip.

How am I going to get there? Ask yourself Where am I? Where am I going? How am I going to get there?

Neuroplasticity Break

Conversion Factor Examples

More Examples

Examples 1 kilogram = 1000 g

Use conversion factors to convert each of the following 612 dollars to quarters 1 dollar = 4 quarters

537 dollars to nickels 1 dollar = 20 nickels 537 dollars x

Double Conversion!!!!!! 7 days to minutes 1 day = 24 hours 1 hour = 60 minutes

177 millimeters to meters 1 millimeter = 0.001meter

32 kilograms to milligrams Double Conversion!!! 1 kilogram = 1000 grams 1 milligram = 0.001 gram

3.4 liter x 3400 mL 6. 3.4 liter to milliliters 1 millimeter = 0.001 meter 1 milliliter = 0.001 liter 3.4 liter x 3400 mL

Neuroplasticity Time Now take out your practice problems.