Do Now/Agenda Work on measurement/sig figs review problems Today: Finish Unit 1 Next classes: lab and review Unit 1 Test Thur 9/15 (B), Fri 9/16 (A)

Sig Figs Warm Up Don’t round until the very end! Base your rounded answer off of your given measurements/values.

Volume Volume=amount of space an object takes up Ways we can measure volume: For liquids: using glassware When using a graduated cylinder, read the value from the bottom of the meniscus

Volume Ways to measure volume For regular solids: length x width x height

Volume Ways to measure volume For irregular solids: water displacement 40 mL 40-20 = 20 mL

Density Density=the amount of mass in a given volume.

Which cube has a greater density? Both cubes take up the same amount of space (volume), but cube A has more matter (mass)

Using the Density Formula mass density volume

Density Practice: Round answer to proper number of sig figs! 3.23 g/mL 7 g/mL 5 mL 2.0 g/cm3 204 g  2.0 x 102 g 3.23 g/mL, 7.0 g/mL, 5 mL, 6.82 g/mL

Accuracy vs. Precision

Accuracy vs. Precision Accuracy=how close the results are to the correct answer (Bull’s eye!) To determine accuracy, we look at the average of our results. Precision= how often the same results are measured/obtained To determine precision, we look at the consistency of our results.

AVERAGE ACCURATE NO

each trial/measurement precise NO

Accuracy vs. Precision Practice YES YES

Accuracy vs. Precision Practice 4.67 NO 99 YES YES NO

Percent Error A quantitative way we can look at the accuracy of a set of data if the true value is known For this class, we’ll say the data is accurate if the percent error is less than 5%

The freezing point of water is 273. 2 K, but it was measured at 250 The freezing point of water is 273.2 K, but it was measured at 250.1 K. What is the percentage error? Subtract first, then divide, then multiply by 100 23.1 273.2 ×100% 250.1−273.2 273.2 ×100%= =0.084×100% =𝟖.𝟒% NOT ACCURATE

Percent Error Practice 2) 4.49 % 3) 888% 4) 3.88%

Telephone 602,000,000,000,000,000,000,000 6.02 x 1023

Scientific Notation Scientific notation is used to express very large or ­very small numbers more easily. It is written as a (decimal between 1 & 10) x 10 raised to an exponent

How to express a number in terms of scientific notation: 1. Move the decimal point of your number so that you have a decimal between 1 and 10

How to express a number in terms of scientific notation: 2. Count the number of spaces (n) and which direction you moved the decimal point

How to express a number in terms of scientific notation: 3. If you moved the decimal point to the left multiply (x) your decimal by 10n 360,000  3.6 x 105 If you moved the decimal point to the right, multiply (x) your decimal by 10—n 0.00037  3.7 x 10—4

Category Normal Number Scientific Notation Population of the World 7,125,000,000 people   Distance from the Earth to the Moon 240,000 miles Raindrops in a Thundercloud 6,000,000,000,000 drops Density of Oxygen 0.001332 g/cm3 Mass of a Dust Particle 0.000000000753 kg

How to express a value given in scientific notation as a normal number: 1. Identify the exponent 3.6 x 105: exponent 5 3.7 x 10—4: exponent –4

How to express a value given in scientific notation as a normal number: 2. If the exponent is a positive number, move the decimal point the same number of places to the right 3.6 x 105: move decimal 5 places to the right

How to express a value given in scientific notation as a normal number: 3. If the exponent is a negative number, move the decimal point the same number of places to the left. 3.7 x 10—4: move decimal 4 places to the left

Category Normal Number Scientific Notation Speed of Light   3.00 x 108 m/s Distance from the Earth to the Sun 9.3 x 107 miles Cells in the Human Body 1.0 x 1014 cells Water on Earth’s Surface 1.40 x 108 square miles Diameter of a Grain of Sand 2.4 x 10-3 inches

Homework Accuracy, Precision, Density