Chapter 2 Notes I Quantitative/qualitativeAccuracy/precision Standard Units & Metric Conversions

Types of measurements  Qualitative-measurements describing the qualities or characteristics of something  Quantitative-measurements that focus on actual numerical data

What type of data is the following:  The beaker is hot.  The beaker is 37 o C.  A yellow precipitate forms.  Water has a density of 1.0g/ml.

Accuracy vs. Precision  Accuracy-how close a measurement is to the actual value.  Precision-how close a set of measurements are to each other.

What is an example of: -something both accurate and precise. -something precise but not accurate. -something accurate but not precise.

Accuracy and Precision What are the precision and accuracy levels of the following? Low Accuracy High Accuracy Low Accuracy High Precision High Precision Low Precision

Whose data is most accurate/precise? Three chemistry students measured the mass and volume of a piece of zinc to determine it’s density. The table below shows the data: JohnSamSara Trial g/mL 7.65 g/mL 7.04 g/mL Trial g/mL 7.65 g/mL 7.55 g/mL Trial g/mL 7.64 g/mL 7.26 g/mL Average 7.15 g/mL 7.65 g/mL 7.28 g/mL Compare the students data. Whose data is the most accurate and precise?

v What is the mass on this quadruple-beam balance? v What is the smallest place value on this equipment? v What place value should this measurement go to? v What is the measurement? hundredths place hundredths place thousandths place thousandths place grams grams

v What is the mass on this quadruple-beam balance? v What is the smallest place value on this equipment? hundredths place hundredths place v What place value should this measurement go to? thousandths place thousandths place v What is the measurement? grams grams.

The Metric System

What is Metrics?  Based on factors of ten  Also Called International System (SI)

Why use metrics in science?  Factors of ten are much easier to work with.  Research does not just occur in the U.S.—a global community requires a universal measuring system.

Standard Units  Length  Mass  Time  Temperature  Amount of substance meter kilogram second Deg. Celsius mole

Derived Units  Area  Volume  Density  Concentration  Energy Square meter (m 2 ) Cubic meter (m 3 ) Though this is the standard, we will mostly use liters! Kg/m 3 Moles/liter Joules (force x length

Metric Prefixes  Each prefix signifies an amount of base units represented.

v The metric system is base 10 system that only requires the movement of the decimal point to change units. v The prefixes of the metric system are: Mega (M) = **Kilo (k) = Hecto (h) = Deka (da) = **Unit = (liter) (meter) (gram) Deci (d) = Centi (c) = **Milli (m) = mighty king Henry drinks ultra dark chocolate milk units (10 6 ) units (10 3 ) 100 units (10 2 ) 10 units (10 1 ) 1 unit (10 0 ) 0.1 units (10 -1 ) 0.01 units (10 -2 ) units (10 -3 ) **Notice…everything revolves around the unit!!! **width of a dime **about the distance across Texas Metric Prefixes

v To convert b/n units, start at the given and ‘jump’ to the unknown. v If you jump up, move the decimal that many places to the left. v If you jump down, move the decimal that many places to the right. Mega kilo hecto deka unit deci centi milli v Practice: 32.4 g = _________ kg mL = _________ daL m = _________ dm jumped up 3 times = decimal to the left 3 times jumped up 4 times = decimal to the left 4 times jumped down once = decimal to the right once. 6,287 6,287