Lesson 1.1 MEASUREMENT, UNITS, SCIENTIFIC NOTATION, AND PRECISION

Transcription

1 Lesson 1.1 MEASUREMENT, UNITS, SCIENTIFIC NOTATION, AND PRECISION

2 I. Measurements Measurements can be either Qualitative or Quantitative Qualitiative Quality, like a color or smell, are simple observations Quantitative Quantity, meaning numeric We will focus more on the quantitative measurements in this course. All quantitative measurements need to have a number and a unit.

3 II. Units Definite quantity used as a standard for a measurement There are three Basic Units - Length à meters (m) mass à grams (g) (amount of matter, stuff ) volume à liters (L) (3-D space, also m 3 ) But sometimes these aren t be best way to represent a quantitative measurement Many measurements will be multiples of these standards There are two ways scientists commonly deal with multiples: Unit Prefixes Scientific Notation

4 II. Units There are many prefixes for the Metric (SI) system Prefix Symbol Multiplier Exponential yotta Y 1,000,000,000,000,000, 000,000, zetta Z 1,000,000,000,000,000, 000, exa E 1,000,000,000,000,000, peta P 1,000,000,000,000, tera T 1,000,000,000, giga G 1,000,000, mega M 1,000, kilo k 1, hecto h deca da Base Unit Please fill in the bold orange rows.

5 II. Units Exponen Prefix Symbol Multiplier tial Base Unit deci d centi c milli m micro µ nano n pico p femto f atto a zepto z yocto y

6 II. Units We will commonly use prefixed units like milliliters (ml) and centimeters (cm) so it is best to know how to use this chart and convert between prefixed units Ex. #1: How many micrograms (µg) are in grams? 12,250,000 µg Ex. #2: How many nanoliters (nl) are in 33 centiliters (cl)? 330,000,000 nl Ex. #3: How many cubic millimeters are in 1 cubic meter? 1,000,000,000 mm 3

7 III. Scientific Notation The other way to illustrate multiples of very large or small numbers is to use Scientific Notation Most chemistry teachers will tell you a number we use quite often is 602,200,000,000,000,000,000,000 Which is a pain to write out over and over again, so it is commonly condensed using scientific notation, which shows its power of

8 III. Scientific Notation For numbers larger than one: 1. Find the decimal point If none is present, we assume it is at the end 23,000, Move it to the left until it s behind the last number Erase any zeroes on the right Add 10 n where n is the number of spaces you moved the decimal

9 III. Scientific Notation For numbers smaller than one: 1. Move the decimal to the right until it s behind the first non-zero number Erase any zeroes on the left Add 10 n where n is the number of spaces you moved the decimal

10 IV. Accuracy and Precision Accuracy how close a measurement is to the actual value Precision How close different measurements are to one another OR the degree to which a piece of equipment can accurately measure. These are very important topics to the class that we will be considering with almost every experiment or investigation. It is best practice to use the most precise piece of equipment available All measurements must be reported with the correct accuracy.

11 V. Significant Figures Significant Figures or SigFigs are used to reflect how accurate a measurement was. When making a measurement, we use a digit for all possible measurements and one digit for an estimate. All possible measurements means each size of line or graduation.

12 V. Significant Figures It is important to use your measuring tool correctly and report the number to the correct place. If you round a measurement, it may be interpreted as a less precise, and possibly a less accurate, measurement. When looking at a measurement you did not make, we can count the number of significant figures to make a determination about the precision of the tool the researcher used.

13 V. Significant Figures Rules for counting SigFigs 1. Any Non-zero IS significant 124 = 2 sf 2. Any zero before a non-zero IS NOT significant 0012 = 2 sf = 3 sf 3. Any zero between two non-zero numbers IS Significant 103 = 3 sf = 5 sf 4. Any Zeroes after the last non-zero digit IS significant IF there is a decimal point anywhere in the number. If no decimal point, then all zeroes after the last non-zero digit ARE NOT significant 100 = 1 sf = 4 sf