Chem 130 Exam 1

Dividing Scientific Notation

1. divide numbers 2. subtract exponents 3. adjust answer ex.) 6.30 x 10^-3 kg _______________ 9.0 x 10^-6 L = .7 x 10^3 (fix SF) = .70 x 10^3 (fix decimal and exponent) = 7.0 x 10^2 kg/L (add unit)

Adding and Subtracting Scientific Notation

1. make the powers of 10 the same by moving the decimal 2. add numbers 3. adjust answer change to like terms... ex.) 4.20 x 10^3 g 42.0 x 10^2 + 6.00 x 10^2 g = 6.00 x 10^2 _____________ = 48 x 10^2 (fix SF) = 48.0 x 10^2 (fix decimal, change expo) = 4.80 x 10^3 g (add unit)

How to write Scientific Notation: and how to take a decimal out of it

1. move the decimal point so that it is behind the first number 2. multiply by 10 to the power of how many places you moved the decimal <----------------- exponent is positive ------------------> exponent is negative 3. ONLY INCLUDE SIGNIFICANT FIGURES (divide to check your answer) ex.) 23100 m = 2.31 x 10^4 m .0010 L = 1.0 x 10^-3 L 4000 g = 4 x 10^3 g How to take out of Scientific Notation: ex.) 5.2 x 10^-4 m = .00052 m 1.0 x 10^3 g = 1000 g (bar over 2nd 0 to show significance) 4.0 x 10^-2 L = .040 L

Multiplying Scientific Notation

1. multiply numbers 2. add exponents 3. adjust answer to show correct SF, decimal placement, and unit ex.) 2.0 x 10^2 m x 8.10 x 10^4 m ______________ 23.49 x 10^6 (fix SF) 23 x 10^6 ( fix decimal place, will alter exponent) 2.3 x 10^7 (add unit) 2.3 x 10^7 m^2

Potential Energy

energy of POSITION or chemical composition

Kinetic Energy

energy of vibration or MOTION

Rounding answers derived from Multiplication and Division

ex.) ? lb = 1.67 x 10^-18 ug (1 g/ 10^6) (1 lb/453.6 g) = 1.67 x 10^-18 (10^6) (453.6) Step 1: decide which of the numbers in the calculation affect the uncertainty of the answer 1.67 x 10^-18 = the 1.67 DOES affect uncertainty because it is a rounded calculation. 10^6 = an EXACT number, not a measurement. DOES NOT affect uncertainty. 453.6 = rounded calculation, DOES affect Step 2: consider the degree of uncertainty in each of our exact values. determine their relative uncertainties by counting the # of significant figures. 3SF in 1.67 x 10^-18 4SF in 453.6 * the # of SF reflects the degree of uncertainty in the value - larger # of SF = smaller uncertainty Step 3: reflect the most uncertain value used in our calculation 1.67 x 10^-18 ug has 3SF so... we round the calculated result of 3.681657848325 x 10^-27 to... 3.68 x 10^-27

Derived Unit

use of 2 or more base units (ex. km/hour)

Rounding and Significant Figures

* Rounding should be expressed in a way that reflects the proper degree of uncertainty. ex.) ? lb = 4.9800 g (must convert g to lb - how many grams are in 1 pound?) = 4.9800 g (1 lb/453.6 g) <--- g cancel out = 4.9800/ 453.6 = 0.010978 ( move decimal to express SF) 1 lb = 1.098 x 10^-2 lb

Percentage by Mass

* a value that tells us the # of mass units of the part for each 100 mass units of the whole. ex.) 8.0 kg blood or 8.0 g blood or... ___________ ___________ 100 kg body 100 g body for x % by mass... x (any volume unit) part ____________________ 100 (same mass unit) whole

Rules for determining SIGNIFICANT FIGURES

* all digits 1-9 are significant ex.) 3.4g = 2SF) * leading zeros are NEVER significant ex.) 0.00422 m = 3SF * in between zeros are ALWAYS significant ex.) 10.04s = 4SF * trailing zeros are ONLY significant if there is a decimal point or a bar somewhere ex.) 120.0 m = 4SF 2000 g = 1 SF

Dimentional Analysis

* converting from one unit to another using conversion factors which come from EQUALITIES. * conversion factors = ratios that equal 1; can be identified by the word "per". ex.) 1 foot = 12 inches 1 foot/ 12 inches or 12 inches/ 1 foot

Accuracy - reporting values from measurements

* how closely a measured value approaches the true value of the property. ex.) penny true mass = 2.525 g 5 students use the same balance to report slightly different values: 2.680, 2.681, 2.680, 2.679, 2.680 range of values = +/- 0.001 g of 2.680 g 2.680 - 2.525 = o.155 g (inaccurate by this) * scientists assume that the number in the last reported decimal place has an uncertainty of +/- 1, unless stated otherwise. * trailing zeros ex.) if the measurement is right at the 8 mL mark, you would report 8.00 mL to recognize that it was between 7.99 mL and 8.01 mL

Precision - reporting values from measurements

* how closely a series of measurements of the same object resemble each other. closer = more precise * precision does not necessarily equal accuracy *ALL MEASUREMENTS ARE UNCERTAIN TO SOME DEGREE

Properties of Matter

* physical properties are observable without changing the identity of the substance. physical states: solid liquid gas (plasma) ALSO... color, texture, luster, conductivity (heat transfer), melting point (solid to liquid), boiling point (liquid to gas), solubility (does it dissolve), density (closely packed particles), specific heat capacity

Addition and Subtraction - calculations with SF PLACE

* the answer must be rounded so that it reflects the accuracy of the WORST measurement ex.) 6.25 g + 4.1 g = ? calculator says 10.35 g, but according to the rule, we can only go to the tenths place. so... 6.25 g + 4.1 g = 10.4 g

Multiplication and Division - calculations with SF COUNT

* the product or quotient should be rounded to the same number of significant figures as in the measurement with the fewest significant figures ex.) 9.5 cm * 5 cm = ? calculator says 47.5 cm^2 but, according to the rule we can only have the same number of SF as the factor with the LEAST amount of SFs. so... 9.5 cm * 5 cm = 50 cm^2 (the zero here is a placeholder)

Kelvin - K

* the value of K = absolute zero, always designed to equal C * ABSOLUTE ZERO = the point beyond which the motion of the particles (and therefore the temp.) cannot be decreased. 0 K = -273.15 C = -459.67 F

Measurement Method

* write a number for each place that the instrument has marks for; the KNOWN number *add a number for ONE estimated place _100s_ _10s_ _1s_ . _10ths_ _100ths_ _1000ths_

Mass

*a measurement of the AMOUNT OF MATTER in an object *the property of matter that leads to gravitational attractions between object and therefore gives rise to weight.

Celsius - C

0 degrees C = temp. at which water freezes 100 degrees C = temp. at which water boils * thus, a degree Celsius is 1/100 of the temp. difference between freezing and boiling water

Measurement in Scientific Notation

2.10 x 10^6 mg 2.10 = significant 10^6 = not significant ex.) 2040 m = 3SF 0.010 g = 2SF 200 L = 1SF 2.12 * 10^3 s = 3SF 60,606,000 = NOT A MEASUREMENT/ NO SF 36 students = NOT A MEASUREMENT/ NO SF

Fahrenheit - F

32 degrees F = temp. at which water freezes 212 degrees F = temp. at which water boils * a degree Fahrenheit is 1/180 of the temp. difference between freezing and boiling (212-32 = 180) *a F is smaller than a C - there are 180 F per 100 C ( 1.8 F per 1 C)

Specific Heat Capacity

AMOUNT OF HEAT ENERGY required to raise the temperature of 1 gram of a substance by 1 degree; C= q/m * AT

Calorie

AMOUNT OF HEAT ENERGY required to raise the temperature of 1 gram of water to 1 degree celcius

Unit Analysis Process

Convert 4567. 36 micrograms to kilograms. ? kg = 4567.36 ug (1 g/ 10^6 ug) (1 kg/ 10^3 g) * remember to cancel out like units = 4567.36 (1 kg/ 10^9) fix decimal placement which also changes exponent = 4.56736 x 10^-6 kg add unit

Prefixes *** MUST be attached to a unit. NEVER use a prefix alone (ex. a kilo of beans)

Giga (G) 1,000,000,000 x = 10^9 Mega (M) 1, 000, 000 x = 10^6 Kilo (K) 1, 000 x = 10^3 Hecto (h) 100 x = 10^2 Deca (da) 10 x = 10 Deci (d) 1/10 x = 10^-1 Cemti (c) 1/100 x = 10^-2 Milli (m) 1/1000 x = 10^-3 Micro (u) 1/1,000,000 x = 10^-6 Nano (n) 1/1,000,000,000 x = 10^-9

METRIC SYSTEM

Using METER for distance: *from bottom to top, multiply by 10 at each unit to get the measurement you need ex.) how many centimeters in a kilometer? centimeter is 0 x 10 at decimeter = 10 x 10 at meter = 100 x 10 at decameter = 1000 x 10 at hectometer = 10,000 x 10 at kilometer = 100,000 = 100,000 cm King kilometer Henry hectometer Died decameter By BASE - METER Drinking decimeter Chocolate centimeter Milk millimeter m= meter = distance l = liter = volume g = gram = weight

Appropriate Units

Width of a pencil? milliimeters Mass of an elephant? kilograms Area of the room? meters^2 Area of a bacteria colony? micrometers ^2 Volume of a water droplet? mL Distance to the moon?

Temperature

a measure of KINETIC ENERGY

Weight

a measure of the FORCE of gravitational attraction between it and a significantly large body, such as Earth or the Moon.

Density

a measure on COMPACTNESS; D= mass/volume

Significant Figure

a number in a MEASUREMENT

Endothermic

a process that ABSORBS energy

Exothermic

a process that RELEASES energy

Conversion Factor

a ratio that is equal to one and is used to CONVERT from one unit to another: 1 foot/12 inches

Sublimation

change in physical state of a substance FROM A SOLID TO A GAS (ex. dry ice)