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I. Chemistry Today * chemistry – the study of the materials that make up the universe and the changes they undergo II. Scientific Method – a systematic approach to research which all scientists follow A) Stating a problem B) Researching the nature of the problem - assign variables 1. independent variable – the pre-determined variable in an experiment; x-axis 2. dependent variable – the measured variable in the experiment; y-axis C) Forming a hypothesis D) Designing an experiment E) Collecting data 1) qualitative data – general observations 2) quantitative data – data containing numerical measurement F) Using data to decide validity of hypothesis - forming a theory III. Basic Defenitions of Matter A) Matter – anything that has mass and occupies space B) Mass – a measure of the amount of matter in an object * weight – the reaction of gravity to mass; varies with location C) Substances – a form of matter with constant composition; 2 groups of pure substances: 1) compound – a chemical combination of 2 or more elements with a fixed proportion of atoms in it; requires chemical process to separate 2) element – substances that can not be broken down by any chemical means * represented by a one or two-lettered symbol D) Mixtures – non-chemical combinations of 2 or more substances; composition can vary * can be easily separated without changing the components 1) homogeneous mixture – one that appears the same throughout 2) heterogeneous mixture – one in which the separate components are visible E) Physical Change – can be observed without modifying the substance F) Chemical Change – observed as a result of a chemical change

Matter

Mixtures

Homogeneous

Heterogeneous

Substances

Compounds

Elements

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IV. Graphing. A visual way to see patterns in data. In this class we will always use a standard Cartesian graph (squares of equal value) * x-axis – horizontal axis; represents the independent variable * y-axis – vertical axis; represents the dependent variable directly proportional – as “x” increases, “y” increases

x =K y

inversely proportional – as “x” increases, “y” decreases

OR y = Kx

xy = K OR

y=

K x

S. After doing an experiment on the effect of temperature on the time for dissolving a sugar cube, you obtain the following data:

Temp (oC) Time (s) Temp (oC) Time (s) Temp (oC) Time (s) Temp (oC) Time (s) 20 25 30 35

68.1 64.9 61.7 58.5

40 45 50 55

55.3 52.1 48.9 45.7

60 65 70 75

42.5 39.3 36.1 32.9

80 85 90 95

29.7 26.5 23.3 20.1

1. Graph the data on the sheet of graph paper below. Be sure to properly title the graph and label your axes.

2. Is this directly proportional,

inversely proportional, or neither? Neither

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3. Draw a best-fit line through your data. Choose two points which fall on the line and use them to find the slope.

slope =

y 2 − y1 61.7 − 68.1 = = −0.64 x 2 − x1 30 − 20

4. Choose one of the two points you used and find the equation for the line. Be sure to express your equation in the form: y = mx+b. Rewrite this equation substituting “T” for x, and “t” for y.

y = mx + b → 68.1 = (−0.64)(20) + b 68.1 = −12.8 + b → b = 68.1 + 12.8 = 80.9 t = −0.64T + 80.9 5. What should the dissolving time be at a temperature of 5oC?

y = −0.64 x + 80.9 = (−0.64)(5) + 80.9 = 77.7 sec 6. Estimate the time required to dissolve a sugar cube in boiling water (100oC).

y = −0.64 x + 80.9 = (−0.64)(100) + 80.9 = 16.9 sec 7. Describe what you think would happen to the data (and therefore the graph) if there were already 3 sugar cubes dissolved in the beaker before performing the experiment. The dissolving times would most likely all increase by the same amount. This would cause the graph to have the same slope, but a higher y-intercept. V. The Laboratory A. Equipment with which you should be familiar:

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B. Symbols you should know: SYMBOL

MEANING

SYMBOL

MEANING

Flammable Solid

RED - Flammable Gas or Liquid BLUE – Dangerous when wet

Poisonous

Strong Oxidizer

Radioactive

Corrosive

Strong Irritant

Biohazard

C. Important Safety Rules to know: 1. Never directly smell or taste anything in the lab – learn to waft if smell is needed. 2. When diluting an acid, always add acid to the water, especially with H2SO4. 3. Always READ THE DIRECTIONS FIRST!!!!! 4. Stick to the lab directions. Unauthorized experiments = trouble. 5. Always work with good ventilation. 6. Always heat substances slowly. 7. Always weigh objects using a weigh boat, beaker, or other container. 8. Always use the maximum number of significant digits allowed by your measuring device.

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VI. Handling Numbers A) Significant Figures 1) Basic Rules: a. All digits 1-9 are significant b. All zeros in a “sandwich” are significant c. All zeros that end a decimal fraction are significant d. All zeros in front of a fraction and not in a sandwich are not significant e. All zeros at the end of a number greater than 10 not in a sandwich are not significant. f. A “lined” zero (θ) is significant. * Try the “Atlantic-Pacific” rule to remember: - If the decimal point is Present, count from the Pacific side - If the decimal point is Absent, count from the Atlantic side 2) Multiplying and Dividing * When multiplying and dividing measurements, the answer should have a number of significant figures equal to the multiplicant with the least number of sig figs For example:

36.2 x

4.3 = 155.66 2 sig figs

3 sig figs

Calculator answer; needs to be rounded to 2 sig figs

155.66 Keep these 2 digits

160 Drop these digits

Final Rounded Answer

3) Adding and Subtracting * When adding and subtracting measurements, round your answer to the decimal place represented by the least precise number – round it to the “worst” decimal place For example: Nearest 1’s digit Nearest 0.01 Nearest 10’s digit

123 40.55 + 270 433.55

123 40.55 + 270 433.55 Keep this

drop this

Perform the following: 1) 11,254.1 + 0.1983

2) 66.59 – 3.113

11,254.3

63.48

3) 8.16 x 5.1355

41.9

4) 0.0154 / 883

1.74 x 10-5

430

UNIT I – CHEMICAL FOUNDATIONS B) Scientific Notation base - must be greater than or equal to 1 and less than 10

4.56 x 10

6

power

5

* the number of sig figs in a number expressed in scientific notation corresponds to the number of sig figs in the base number Express the following in scientific notation: 1) 568.672

2) 0.00000772

5.68672 x 102

7.72 x 10-6

Express the following as decimal numbers: 1) 3.54 x 10-8

2) 9.010 x 107

0.000 000 0354

90,1θ0,000

Perform the following calculations. Make sure your answers are rounded to the correct number of sig figs.

1)

(5.444 x108 )(1.0001x10 −23 ) = (2.43 x10 −10 )(5.3063 x1030 )

(5.0404 x10 −22 )(3.2 x105 ) 2) = (7.020 x10 −10 )(6 x10 40 )

4.22 x 10-36

4 x 10-48

C) Accuracy vs. Precision – look at the following measurements: * accuracy - how close a measurement is to the actual value * precision – how close a set of measurements are to each other

Actual Value: 3.532 m Trial 1 3.539m Trial 2 3.530m Trial 3 3.529m These measurements are both accurate (close to the actual value) and precise (close to each other)

Actual Value: 3.532 m Trial 1 4.192m Trial 2 0.035m Trial 3 10.112m These measurements are neither accurate nor precise

Actual Value: 3.532 m Trial 1 4.523m Trial 2 4.520m Trial 3 4.529m These measurements are not accurate, but they are precise. Perhaps the measuring device is uncalibrated or the procedure is faulty.

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VII. Measurement – gives quantities in a way that all can understand A) Units – scientists use the SI system (Systeme’ Internationale)

Unit

Abbreviation Quantity Measured

meter gram second mole Kelvin

m g s mol K

length mass time number of items temperature

* When a base unit is too big or too small for the measurement you are performing, a prefix can be added to change the unit: Which unit would be appropriate to measure the: Tera-

(T-)

1) distance from Holland to Detroit?

kilometers (km) Giga- (G-)

2) volume of vaccine administered in a shot?

mL (cm3 or cc)

Mega- (M-)

3) mass of an atom?

kilo- (k-)

picograms (pg) or smaller? (base) deci- (d-) centi- (c-) milli- (m-)

4) width of a proton?

nanometers (nm) 5) volume of a tank of gasoline?

micro- (µ-)

liters (L)

nano- (n-)

6) number of bytes of memory on your computer’s hard drive?

Gigabytes (GB)

pico- (p-)

* there are also base units for charge and light intensity (Coulomb and Candela) * there are combined units for: 1) Volume * 1 mL = 1 cm3 1L

g

= 1 dm3

mL

4) Pressure Pascals (Pa) kg m• s 2

=

N

2) Density

=

3) Velocity

m

g cm 3

5) Energy Joules (J) m2

= Pa

kg •m2 s2

s

6) Force Newtons (N)

=J

kg • m s2

=N

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VIII. The Factor-Label Method of Solving Problems – Dimensional Analysis * requires a known value and an equivalency * example: I know 1m = 1000mm. How many meters are equivalent to 2430mm? 1. Write down the known value.

2430mm

2. Set up your conversion factor.

2430mm x _________

3. Match units on the bottom of the conversion factor with the known value.

4. Put the units desired on the top.

2430mm x

5. Place the known equivalency into the conversion factor.

2430mm x

m mm 1 m 1000 mm

2430 mm x 1 m = 2.43 m 1000 mm

6. Simplify. DEFINITIONS 1 ton = 2000 lbs 16 oz = 1 lb 1 gal = 4 qts 1 foot = 12 in

2430mm x _________ mm

APPROXIMATIONS 1 inch = 2.54 cm 1 liter = 1.06 qts 1 km = 0.6214 mi 1 kg = 2.2046 lbs

Perform the following operations: 1) 5.6 dm = ? m

2) 0.504 L = ? mL

1m 5.6dm ∗ 1 = 0.56m 10 dm 3) 3.55 x 108 mg = ? kg

3.55 x10 8 mg ∗

4) 2.06 x 10-5 km = ? cm

1kg = 355kg 10 6 mg

5) 45.5 cm = ? in

45.5cm ∗

2.06 x10 −5 km ∗

10 5 = 2.06cm 1km

6) 162 lbs = ? g

1in = 17.9in 2.54cm

7) 14.3 gallons = ? L

14.3 gal ∗

103 mL 0.504 L ∗ = 504mL 1L

4qts 1L ∗ = 54.0 L 1gal 1.06qts

9) 3.45 x 10-5 g/mL = ? g/L

3.45 x10 −5 g 103 mL ∗ = 0.0345 g L mL 1L

1kg 103 g ∗ = 73,500 g 2.2046lbs 1kg

162lbs ∗

8) 25 miles/hr = ? km/hr

25mi 1km ∗ = 4θ km hr hr 0.6214mi 10) 6.2 m3 = ? cm3

(10 ) cm 2 3

6 .2 m 3 ∗

1m

3

3

= 6.2 x10 6 cm 3

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IX. Density - an intensive property; what does that mean? The property does not depend on the size of the sample. Mass and volume are examples of extensive properties (they depend on sample size).

Densities of Some Common Densities of Some Common Gases at 25oC Liquids at 25oC Substance Hydrogen Helium Air Oxygen SF6

Density (g/L) 0.0837 0.179 1.28 1.33 6.52

Substance Ether Ethanol Water Mercury

Density (g/mL) 0.719 0.781 1.00 13.3

Densities of Some Common Solids at 25oC

Substance Styrofoam Sodium Magnesium Aluminum Iron

Density =

Density (g/mL) 0.145 0.68 1.38 2.70 7.86

Substance Copper Silver Lead Gold Osmium

Density (g/mL) 8.96 10.50 11.34 19.30 22.6

mass Volume

1) What is the density of a cube with sides 2.51cm in length which has a mass of 27.1g?

V = (2.51cm)3 = 15.813251cm 3 → D =

m 27.1g = = 1.71 g cm3 V 15.8cm 3

2) What is the mass of 50.0 mL of water? ethanol?

m m → 1.00 g mL = → m = (1.00 g mL )(50.0mL) = 50.0 g V 50.0mL m m D = → 0.781 g mL = → m = (0.781 g mL )(50.0mL) = 39.1g V 50.0mL

D=

3) If the mass of the copper rectangular solid below is 154.82g, what is the length of side “x”?

x

m 154.82 g → 8.96 g mL = → (8.96 g mL )V = 154.82 g V V 154.82 g V= = 17.279mL = 17.279cm 3 = (5.4cm)(1.0cm) x → x = 3.2cm g 8.96 mL D=

5.4 cm 4) Diamonds are measured in carats, and 1 carat = 0.200g. The density of diamond is 3.51 g/cm3. What is the volume of a 5.0-carat diamond?

5.0carats ∗

0.200 g 1cm 3 ∗ = 0.28cm3 1carat 3.51g

1.0 cm