Measurements and Calculations

Measurements are quantitative data that scientists obtain “Measurements represent quantities” (Davis, Saquis, Frey and Saquis 33) Quantity = “something that has magnitude, size, or amount” (Davis et al. 33) Example: volume “A quantity is not the same as a measurement” (Davis et al. 33) Volume is a quantity Teaspoon is a unit of measurement for volume Measurements need a number and a unit! Speed Limit = 50 Distance traveled = 5 Without units, the numbers don’t make sense

Le Système International d’Unités (SI) Different standards used to be used to measure things By having different standards for measuring things, data can be confusing Scientists developed a list of common standards of measurements to be universal This is called the SI system

Le Système International d’Unités (SI) There are seven base units Quantity SI Unit Abbreviation Length meter m Time second s Mass kilogram kg Amount of Substance mole mol Temperature kelvin K Electric Current ampere A Luminous intensity candela cd

SI Units “defined in terms of standards of measurement” (Davis et al. 33) “The standards are objects or natural phenomena that are of constant value, easy to preserve and reproduce, and practical in size” (Davis et al. 33)

SI Base Units Length SI Base Unit = meter (m) Can be measured using a meter stick “A distance of 1 m is about the width of an average doorway” (Davis et al. 35) The meter can be adjusted with prefixes kilometer = 1000 meters centimeter = 1/100 meter Time = “interval between two occurrences” (“Chapter 1: Measurements and Calculations”) SI Base Unit = second (s)

SI Base Units Mass = “a measure of the quantity of matter” (Davis et al. 34) SI Unit Name = kilogram (kg) (about the mass of a textbook (Davis et al. 35)) 1 kg = 1000 grams Smaller masses are typically measured in grams (1/1000 kg) or even smaller masses in milligrams (1/1000000 kg) Mass can be measured using an electronic or triple beam balance Mass is not the same as weight! Weight is the measure of the Earth’s gravitational pull on an object Weight varies according to distance from Earth The farther you are away from Earth, the less weight you have. You will still have the same mass though! Davis, Raymond E., Mickey Sarquis, Regina Frey, and Jerry L. Sarquis. Modern Chemistry. Austin: Holt, Rinehart and Winston, 2009. Print.

SI Base Units Amount of substance (Davis et al. 34) Temperature SI Unit Name = mole (mol) “the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon-12” (Davis et al. 34) Temperature SI Unit Name = kelvin (K) kelvin temperature = 273.15 + °C

SI Base Units Electric current = “the time rate of flow of electric charge, in the direction that a positive moving charge would take and having magnitude equal to the quantity of charge per unit time” (“electric current”) SI Unit Name = ampere (A) Luminous Intensity = “a measure of the amount of light that a point source radiates in a given direction. It is expressed by the luminous flux leaving the source in that direction per unit of solid angle” (“luminous intensity”). SI Unit Name = candela (cd)

Works Cited “Chapter 1: Measurements and Calculations.” Course notes. Honors Chemistry Level 5. Department of Science, Serra Catholic. 30 September 2016. Davis, Raymond E., Mickey Sarquis, Regina Frey, and Jerry L. Sarquis. Modern Chemistry. Austin: Holt, Rinehart and Winston, 2009. Print. "electric current". Dictionary.com Unabridged. Random House, Inc. 4 Oct. 2016. <Dictionary.comhttp://www.dictionary.com/browse/electric-current>. "luminous intensity". Collins English Dictionary - Complete & Unabridged 10th Edition. HarperCollins Publishers. 4 Oct. 2016. <Dictionary.com http://www.dictionary.com/browse/luminous-intensity>.