Section 2: Measurements and Calculations Unit 1: Matter and Energy

Scientific Method TheoryPublish Results

Units of Measure Qualitative Descriptive (Non-numeric) The fact that the sky is blue Quantitative Measurement (Numeric) A sample of copper ore has a mass of 25.7 grams

Units of Measure The International System (SI)--1960s Commonly used SI units in CHEMISTRY: 1. Lengthmeters (m) 2. Masskilograms (kg) 3. Timeseconds (s) 4. Quantitymoles (mol)

Units of Measure SI units PREFIXES Prefix Symbol How many in a base unit? Nano- n1,000,000,000 Micro- μ 1,000,000 Milli- m1,000 Centi- c100 Deci- d10 PrefixSymbol How many base units? Kilo- k1,000 Mega- M1,000,000 Giga- G1,000,000,000 Example:1 m = 100 cm 1 g = 1,000 mg Example: 1 km = 1000 m 1 mg = 1,000,000 g

Units of Measure Derived Units: A combination of SI base units. Examples: Volume, Velocity, Density Conversion Factors Math used to relate 2 units that measure the same quantity (written as a fraction); Equal to 1 Example1 m = 1000 mm

Units of Measure Conversion Factor Practice Example 1 – Convert 22,000 g to kg. Example 2 – Convert m to mm. Example 3 – How many seconds are in 3.11 hours?

Units of Measure Example 1 – Convert g to kg g x 1 kg = kg = g 1000 Example 2 – Convert m to millimeters m x 1000 mm = 29 mm = 1 1 m 1 Example 3 – How many seconds in 3.11 hours? 3.11 hours x 60 min x 60 sec = sec = 1 1 hr 1 min 1 22 kg 29 mm sec

Using Scientific Measurement  Accuracy  Precision Closeness of a measurement to the true or CORRECT value. How close a set of measurements are to one another, regardless of correctness

Using Scientific Measurement Experiments will always have errors. (human, mechanical, environmental) PERCENT ERROR determines the accuracy of the experiment. (the lower the percent, the better)

Using Scientific Measurement Significant Figures. All digits that occupy places for which ACTUAL measurement was made, including the last estimated digit. When taking measurements, you ALWAYS read the instrument to one more place than is marked. You estimate that digit. See Significant Figures/Scientific Notation Rules/Reference Sheet

Significant Figures Practice 1) sig. figs. 2) sig. figs. 3) sig figs. 4) sig. figs. 5) sig. figs.

Math w/ Sig. Figs. Put answers in correct Sig. Figs. 1) = ) 1500 – – = 948 3) (9.554)(5.10)(1.5) = 73 4) / = 189.6

Using Scientific Measurement Scientific Notation How scientists show either BIG or SMALL numbers. i.e. 602,200,000,000,000,000,000,000 = x Hint: Positive exponents – Move decimal to the right. Negative exponents – Move decimal to the left. Note: Only the numbers before the scientific notation are significant. (6.022 x has 4 sig figs)

Scientific Notation 1) Put in scientific notation 3.25 x ) Put in scientific notation x ) Put 7.54 x 10 4 in regular notation ) Put x in regular notation

Using Scientific Measurement Direct proportionInverse Proportion As one variable increase, so does the other. Penny Lab: Mass v. Volume. As you increased the mass of the stacks of pennies, the volume also increased. As one variable increases, the other decreases