Turn in Homework

Journal: Warm Up1. 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• 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 SNa Mg K Ca Cl F AlFe 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: 67,500,000,000,000.0Decimal 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:

a. 86700000

b. 0.00000052

c. 63100

Journal #4

Now its your turn!!!!

Convert the following values into scientific notation:

a. 86700000 = 8.67 x 107

b. 0.00000052 = 5.2 x 10-7

c. 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

• Error = accepted value - experimental value

• Percent error = ___|error | ___ x 100accepted value

Journal #5• 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. 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 FiguresHow 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• 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

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 5 sig figs• 3.967 has 4 sig figs• 9.006 has 4 sig figs• 0.0004 has 1 sig fig • 8.1000 has 5 sig figs• 501.040 has 6 sig figs• 3,000,000 has 1 sig fig• 10.0 has 3 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