Turn in Homework Journal: Warm Up 1. Explain the difference between a physical and chemical change. 2. Explain the difference between homogenous and heterogeneous mixtures. 3. What are 3 ways that a mixture can be separated?

2.2 & 2.3 & 2.4 Notes

Element vs. Compound 2 or more elements combined Simplest form of matter Can NOT be separated into simpler substances by chemical means Building blocks of other substances Examples: oxygen, hydrogen, etc 2 or more elements combined Substance that can be separated into simpler substances by chemical means H2O

Properties of compounds compared to the elements Sugar, C6H12O6: sweet, white, edible Carbon, C: black, tasteless solid Other interesting examples Salt, NaCl 2 Na + Cl2 = 2 NaCl

Symbols and Formulas Chemical Symbol: a one or two letter symbol for the name of an element Journal #1: Element symbols that you must memorize the name!!!! C H He N O P S Na Mg K Ca Cl F Al Fe Cu Ag Au Hg Pb Sn

Chemical Reactions: Chemical Change Changing reactants to products Reactants: starting substances Products: substances that are formed Equation example Reactants  Products H2 + I2  2 HI(g)

Journal #2: Write down the following chemical reaction NH4NO3  N2 + O2 + H2O Label the reactants and products

Conservation of Mass Mass is neither created nor destroyed Total mass of reactants = total mass of products

Journal # 3 NH4NO3  N2 + O2 + H2O When 20 grams of ammonium nitrate (NH4NO3) break down, 7 grams nitrogen (N2) and 4 grams of oxygen (O2) form. How many grams of water are formed?

Journal # 3 Answer NH4NO3  N2 + O2 + H2O 20 grams = 7 g + 4 g + X g When of ammonium nitrate (NH4NO3) break down, 7 grams nitrogen and 4 grams of oxygen form. How many grams of water are formed? X = 20 - 7- 4 = 9

During any chemical reaction, the amount of matter is unchanged!!! Mass is neither created nor destroyed Matter is neither created nor destroyed

3.1 The Importance of Measurement

Scientific Notation Mathematical abbreviation for measured values Coefficient x 10n The coefficient is greater than or equal to one and less that 10. Example: 67,500,000,000,000.0 Decimal moves 13 places to the left 6.75 x 1013

Example: 0.00000489 Decimal moves 6 places to the right 4.89x10-6

Journal #4 Now its your turn!!!! Convert the following values into scientific notation: 86700000 0.00000052 63100

Journal #4 Now its your turn!!!! Convert the following values into scientific notation: 86700000 = 8.67 x 107 0.00000052 = 5.2 x 10-7 63100 = 6.31 x 104

Accuracy Measure of how close a measurement comes to to the actual or true value of whatever is measured

Precision Measure of how close a series of measurement are to one another Depends on more than one measurement!

Error accepted value Error = accepted value - experimental value Percent error = ___|error | ___ x 100 accepted value

Journal #5 accepted value Error = accepted value - experimental value Percent error = ___|error | ___ x 100 % accepted value You measured the diameter of a ball to be 0.489 m. The package states that the ball has a diameter of 0.5 m. Identify the error and percent error of your measurement.

You measured the diameter of a ball to be 0. 489 m You measured the diameter of a ball to be 0.489 m. The package states that the ball has a diameter of 0.5 m Error: 0.5 - 0.489 = 0.011 Percent error = 0.011 x 100 = 2.2 % 0.5

Significant Figures How do we round in Chemistry??? Significant Figures give the reader an idea of how well you could actually measure/report your data. Rules for significant figures: 1) ALL non-zero numbers (1,2,3,4,5,6,7,8,9) are ALWAYS significant. 2) ALL zeroes between non-zero numbers are ALWAYS significant. 3) ALL zeroes which are SIMULTANEOUSLY to the right of the decimal point AND at the end of the number are ALWAYS significant. (2.400) 4) ALL zeroes which are to the left of a written decimal point and are in a number >= 10 are ALWAYS significant. (300.0)

How Many sig figs? 49,582 has __ sig figs 3.967 has __ sig figs Rules for significant figures: 1) ALL non-zero numbers (1,2,3,4,5,6,7,8,9) are ALWAYS significant. 2) ALL zeroes between non-zero numbers are ALWAYS significant. 3) ALL zeroes which are SIMULTANEOUSLY to the right of the decimal point AND at the end of the number are ALWAYS significant. (2.400) 4) ALL zeroes which are to the left of a written decimal point and are in a number >= 10 are ALWAYS significant. (300.0) 49,582 has __ sig figs 3.967 has __ sig figs 9.006 has __ sig figs 0.0004 has __ sig fig 8.1000 has __ sig figs 501.040 has __ sig figs 3,000,000 has __ sig fig 10.0 has __ sig figs

How Many sig figs? 49,582 has 5 sig figs 3.967 has 4 sig figs

Using rounding in calculations Addition/Subtraction: The answer to an addition or subtraction problem should be rounded to the same number of decimal places as the measurement with the least number of decimal places. Example: 900.049 + 2.2 = 902.249 needs to be rounded to 902.2

Multiplication/Division: answer needs to be rounded to the same number of significant figures as the measurement with the least number of significant figures Example: 200 x 4.579 = 915.8 needs to be rounded to contain only 1 significant figure so your answer is 900

The End