1.3: Measurement and Scientific Notation

Unit I Quiz Get a partner. Get a whiteboard, piece of paper towel, and marker Review your notes with your partner until the bell rings

SI Units of Measurement A measurement must have a number and a unit in order to makes sense. Units such as inches, feet, °F are not used in science Scientists use a set of measuring units called SI, or the International System of Units. Scientists can interpret one another’s measurements using SI.

Base and Derived Units SI Units of Measurement: base units and derived units SI is built upon seven metric units (base units) Base unit: length (meter), mass (kg)

Base and Derived Units SI Units of Measurement: base units and derived units Derived units: units made from combinations of base units Ex. Density (mass/volume)=kg/m3

Metric System SI Units of Measurement: Metric Prefixes A metric prefix indicates how many times a unit should be multiplied or divided by 10. Sometimes units have to be converted to other units (grams to kilograms)

Metric System Conversion Factor: a ratio of equivalent measurements that is used to convert a quantity expressed in one unit to another unit Example: 1 kilometer (km) = 1000 meters (m) OR 1000 meters (m) = 1 kilometer (km)

1.3: Metric Mania - Handout

Precision in Measurement Precision: a gauge of how exact a measurement is If a measurement has more significant figures, it is more precise. Significant figures: all the digits that are known in a measurement, plus the last digit that is estimated. Example: 2.5 = two significant figures (sig figs) Example 2: 3.156 = four significant figures (sig figs)

Precision in Measurement The precision of a calculated answer is limited by the least precise measurement used in the calculation. Example: 2.5 x 3.156 = 7.89 = 7.9 2.5 is the least precise (contains two significant figures, while 3.156 contains four significant figures)

Accuracy in Measurement Accuracy: the closeness of a measurement to the actual value of what is being measured Example: the actual time is 8:35 pm. A clock with 8:32 pm is more accurate than a clock with 8:30 pm.

Measuring Temperature Temperature: a measure of how hot or how cold something is [base unit is Kelvin (K)] Thermometer: device used to measure temperature Two most familiar scales: Celsius and Fahrenheit (Fahrenheit is not used in science) Water Boils at 100° C = 212° F Water Freezes at 0° C = 32° F

Measuring Temperature Temperature can be converted from Fahrenheit to Celsius to Kelvins. ° F = 1.8 (° C) + 32 ° C = (° F ) / 1.8 – 32 ° K = ° C + 273.15 Note: Fahrenheit cannot be converted directly to Kelvins. 0 ° Kelvin: lowest possible temp that can be reached (absolute zero). 0 ° K = -273.15 C

1.3: Metric Worksheet - Handout

Measurement Lab

Scientific Notation Scientific notation: a way of expressing a value as the product of a number between 1 and 10 and a power of 10 Used when working with very large or very small numbers. Example: 6,000,000=6.0 x 106

Scientific Notation 6.0 x 106 (exponent indicates the decimal is really 6 places to the right of the 6) For any number <1, the exponent is negative (exponent indicates the number of places to the left of the number that the decimal is)

Scientific Notation Multiplication: multiply numbers in front of the multiplication sign and add the exponents together Example: (3.0 x 103) x (2.0 x 105) = 6.0 x 108 Division: divide numbers in front and subtract the exponents Example: (8.0 x 1012) / (2.0 x 106) = 4.0 x 106

Section 1.3: Using Scientific Notation

1.3: Scientific Notation – Handout