Chemistry Chapter 2: Analyzing Data 2.1 Units and Measurement *There are 2 important parts to every measurement...the value and the units. *Scientists all over the world use SI units or units from the system international. *A base unit is a defined unit, in a system of measurements which is based on an object or event in the physical world. (See the chart on page 33 for SI base units)

2.1 (Continued) Units and Measurement The SI system uses prefixes to modify a base unit into a measurement that has the right size. (See table of prefixes on Pg 33) To convert metric units into other metric unit values, you only need to move the decimal place. Learn your metric prefixes and base units and learn how to convert from metric values with one metric unit to another.

2.1 (continued) Temperature Scales We use a temperature scale, in science, called the Celsius scale. It is based on the freezing point of water as C and the boiling point of water as C. Most people, in the United states are used to using the Fahrenheit scale of temperature. To convert from o C to o F, o F = 1.8( o C) + 32 To convert from o F to o C, Simply shuffle the algebraic expression to We also use the Kelvin scale of temperature. Absolute zero = o C K= C

2.1(Continued) Derived Units Volume is defined as the space occupied by by an object. The SI unit for speed is m/s. It is a derived unit because it is based on 2 base units. The unit for density, that we will use most often, is g/mL 1 mL = 1cubic centimeter 1 L = 1 cubic deciliter D=m/v

2.2 Scientific Notation Scientists use scientific notation to write values. Scientific notation uses a coefficient, or mantissa, and a power of 10 to represent values. negative exponents represent numbers smaller than 1 and positive exponents represent values greater than 1.

2.3 Accuracy and Precision Accuracy is defined as how close your value is to the actual value of a measurement. Precision is defined as how close measurements are to each other, whether they are close to the real measurement value or not. (See pg. 47)

2.3 (Continued) Error and % Error Error = Experimental value - Accepted value %Error= Exp. value -Acc. value x 100% Acc. value

2.3 Significant Figures Significant figures are important in science. A significant figure is a value that is known. We use a set of rules to establish significant figures aka significant digits.

2.3 (Continued) Significant Figures 1. All non-zero digits are significant. 2. All final zeros, to the right of the decimal, are significant. 3. Any zero between significant digits is a significant digit. 4. Placeholder zeros are not significant. 5. Counting, whole numbers and defined units have unlimited significance.

2.3 Rounding Numbers To round numbers, circle the number of significant digits you want in your final answer, and look at the first value outside of the circle, to the right,...if it is 5 or higher, round the smallest place value in the circle up......if it is 4 or less, just leave the number in the circle as it is.