Catalyst If I wanted to accurately measure 150 mL of potassium chloride solution, what measuring device would I use?

Scientific Notation Short hand for writing very large or small numbers Two parts: Coefficient and Power of 10 A number between 1 and 10 (can include 1 but not 10). Exponent: Must be positive or negative Large numbers have positive exponents! Small numbers have negative exponents!

Scientific Notation Examples: Write the following numbers in scientific notation: 1. 41, ,007, ,000, x x x x x10 8

Calculator time!! Try plugging these into your calculator. Put all answers in scientific notation. *Instead of typing “x 10^,” use the “EE” or “EXP” button!* 37,000 x 7,000= x 0.09= (7x10 6 ) x (8x10 5 )= 2.59x x x10 12

The metric system The International System of Units and A Method of Problem Solving Called Dimensional Analysis Copyright Amy Brown Science Stuff

The International System of Units If everyone is to understand what your measurements mean, you must agree on the units that will be used. By international agreement, a set of units called "The International System of Units" has been defined for scientific work. This system was adopted in 1960 by the General Conference on Weights and Measures. These units are also called metric units or SI units.

SI has seven base units QuantityUnit NameUnit Abbreviation Length meterm Mass kilogramkg Time seconds or sec Temperature KelvinK Amount of Substance molemol Electric Current ampereA Luminous Intensity candelacd

SI has several derived units QuantityUnit NameUnit Abbreviation Hertz frequency1/s Newton forcekg x m/s 2 Pascal pressureN/m 2 Joule energy, work, heat N x m Watt powerJ/s Coulomb charges x A Volt voltageJ/C

SI has several derived units QuantityUnit NameUnit Abbreviation Farad capacitanceC/V Ohm resistanceV/A °C temperatureK Cubic meter* volumem3m3

Advantages of Using SI SI Units make measuring and calculating easier. Measurements are always expressed as decimals rather than fractions. It is very easy to change from one unit to another since they are based on 10. It is universally understood.

SI Prefixes Prefixes can be placed in front of the base units. These prefixes are used to represent quantities that are larger or smaller than the base units. These prefixes must be memorized.

The meter (m) is the SI base unit of length. Prefixes are used to indicate distances longer and shorter than a meter. What name and symbol is given to each of the following units of length? a) m b).001 m c).01 m d).1 m e)10 m f)1000 m Micrometer  m Millimeter mm Centimeter cm Decimeter dm Decameter dam Kilometer km

Volume:Is the space occupied by a sample of matter. The cubic meter (m 3 ) is the SI derived unit for measuring volume. When chemists measure the volumes of liquids and gases, they often use a non-SI unit called the liter. The two units, _________________, are interchangeable. mL and cm 3

State the quantity that is measured by each of the following units: 1. centigram 2. millimeter 3. Kelvin 4. millisecond 1.Mass 2.Length 3.Temperature 4.Time

Mass:The quantity of matter an object contains. Weight : A measure of the pull by earth's gravity. Mass and weight are often confused. Mass is not affected by gravitational pull. Your weight on the moon would be less, but your mass on the moon would be the same. The ____________is the SI base unit for measuring mass. kilogram (kg)

Dimensional Analysis

“Conversion factors” are numbers that are used to change from one unit to another. Conversion factors are formed from equalities that state a relationship between two units. For example: 1 kilometer = 1000 meters. When conversion factors are used properly, all units will divide out (or cancel out) EXCEPT the unit being converted to.

Solving a Problem Using Dimensional Analysis How many kilometers are equal to 250 meters? 250 m 1 kilometer 1000 meters =.250 km When solving a problem using dimensional analysis, start with what you are given in the problem. Decide what conversion factor should be used in the next step. In the conversion factor step, place the unit on bottom that will cancel the unit in the previous step. Proceed until you are left with the unit you are looking for.

Convert.044 km to meters.044 km 1000 m 1 km = 44 m Convert 4.6 mg to grams. 4.6 mg 1000 mg 1 g =.0046 g

Convert 696 cm 3 to m cm 3 (100) 3 cm 3 (1) 3 m 3 = m 3 How many seconds are in.079 years?.079 yr 1 yr 365 days 1 day 24 hr 1 hr 60 min 1 min 60 sec = 2,491,344 sec

Convert.065 km to dm.065 km 1000m10 dm = 650 dm 1 km1 m

Measurements

Measurement: a type of observation Qualitative measurements: descriptive – Ex: hot, cold, heavy, light, big, blue, furry Quantitative measurement: observation made with a measuring instrument and includes both a number and a unit – Ex: ruler, balance, thermometer, graduated cylinder, 13.5°C, 25kg, 17L

Accuracy: How close a measurement is to the true or accepted value – Ex: Weighing a 50g mass 50.00g – accurate 32.18g – not accurate 49.99g – accurate

Precision: How close multiple measurements are to each other – Ex: Take the weight of a 50g massAccurate, precise:50.00g 50.00g49.99g50.00g Not accurate, precise: 32.18g

Three targets with three arrows each to shoot. Can you hit the bull's-eye? Both accurate and precise Precise but not accurate Neither accurate nor precise How do they compare? Can you define accuracy and precision?

An easy way to remember… ACcurate = Correct PRecision = Reproducibility

Always estimate ONE place past the smallest mark!

Reading a Ruler. l I.... I I.... I 5.. cm What is the length of the line? First digit 5.?? cm Second digit 5.1? cm Last (estimated) digit is 5.15 cm

Learning Check. l I.... I 9....I.... I 10.. cm What is the length of the line? 1) 9.6 cm 2) 9.62 cm 3) 9.7 cm How does your answer compare with your neighbor’s answer? Why or why not?