Warm UP (Write these down on the blank piece of paper given to you Warm UP (Write these down on the blank piece of paper given to you. Leave some space in between each.) UNIT 1: Measurement in Chemical Science 1. How do you measure something you can't see? 2. Why does having a standard system of measurement promote advancements in science and technology? 3. How do we know if a measurement is accurate? 4. What effects how significant a measurement is? 5. Why are units needed? 6. How are measurements used in everyday life?

Analyzing Data -Units -Moles -Uncertainty -Significant FIGURES Honors Chemistry with Mr. Morgan 9-13-2010

Chemistry Chemistry is the study of matter and the changes it undergoes. It is largely based on making measurements and analyzing data.

Units and Measurements Measurements tell you 3 pieces of information. The first two are the number and the unit. Why? EX. 10 feet. The unit tells you what’s being measured. The number tells you how much. *The third piece comes a little later.*

Some examples of units How many types of units can we come up with? Pounds, feet, minutes, hours, miles, seconds, rpm’s, m/h, meters/second… There are a lot of different types of units. Can we use just any units in our measurements?

hhhhh Height: about 1 fathom Weight:15 stones Age: 13,674,667.9 minutes Average Salary:30,897,000.00 Russian rubles Do you think this person will be successful in his or her search?

Height: 6 foot Weight: 210 pounds Age: 26 years Average Salary: $1,000,000.00 Units can make the difference

Systeme Internationale International System of Units. There are 7 base units in SI. Why would everyone use a standard system of units? Quantity Base Units Time Seconds (s) Length Meter (m) Mass Kilogram (kg) Temperature Kelvin (K) Amount of Substance Mole (mol) Electric Current Ampere (A) Luminous Intensity Candela (cd)

Million Dollar Unit Blunder

Temperature Conversions If you have Celsius and want Fahrenheit oF= 1.8 (oC) + 32 If you have Fahrenheit and want Celsius oC= (oF) – 32 1.8

Temperature Conversions If you have Celsius and want Kelvin K= (oC) + 273 If you have Fahrenheit and want Kelvin YOU HAVE TO CONVERT FROM (oF) to (oC) before you can go to Kelvin. THERE IS NO DIRECT ROUTE!

Volume How much space something takes up. From your math classes, how do you get the volume of a cube? What would the units be?

Volume The volume of an irregularly shaped object can be found by submerging it in water, and measuring how much the water rose. What would the units be? - Notice how the water is curved? That’s called a “meniscus”. When you see one of those, always read the measurement at eye level and at the center.

Density Measures how much “stuff” is in a certain amount of space. Suit cases 40 pairs 1 bathing 2 shirts of socks suit 1 Pair Jeans

Density How to find density Units ? Example: Density= mass/volume The mass of a sample of a liquid is 10 grams. Its volume is 5 ml. What’s the density? D= 10grams/5ml D= 2g/ml

Uncertainty in Data So far we know a measurement tells you 2 things 1. The number 2. The unit The last thing is how precise the measurement is.

Accuracy and Precision Accuracy: Refers to how close a measured value is to an accepted value. If you weigh a 1 lb. bag of potatoes and the scale reads ½ a lb. then the measurement is NOT accurate.

Accuracy and Precision Precision: Refers to how close a series of measurements are to one another. If I weigh a bag of apples 5 times, and I get the weights 2 pounds, 2.1 pounds, 1.9 pounds, 2 pounds, and 2 pounds, then that scale is relatively precise.

A classic illustration

Precision in measurement The precision in measurement is indicated by the number of digits reported. The reported digits are called SIGNIFICANT FIGURES. This basically says that the more significant figures there are in a measurement, the better the measurement is.

Counting Significant Figures Significant Figures (aka sig figs) include all known digits plus one estimated digit. - Meter stick

Counting significant figures Here’s the easiest way I know to count sig figs THE USA METHOD If the decimal point is Present, start counting from the Pacific side. If the decimal point is Absent, start counting from the Atlantic side. Start counting at the first NON-ZERO. Once you start, don’t stop until you’re out of numbers.

COUNTING SIG FIGS So how many sig figs does each have? 12345 12345. 10000 10000. 0.0000234 10000001