109 CHEM General Chemistry University of Nebraska FALL 2008
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Matter
Anything that has mass and takes up space.
Matter
Pure Substances
Mixtures
Pure substance: matter with _______________ composition Mixture: matter with a ___________ composition
Pure Substances
Element
Compound
Element: form of matter that cannot be broken down into
simpler substances by _____________________________.
Compound: form of matter, made up of two or more elements,
that can be broken down into simpler substances by _____________ _______.
Mixtures
Homogeneous
Heterogeneous
Homogeneous mixture: a uniform mixture of
two or more substance whose ______________________ ______________.
Heterogeneous mixture: a _____________ mixture of
two or more substances whose proportions can be varied.
Properties of Matter
We learn about matter by observing its properties ____________ Properties those which the substance shows by itself without interacting with another substance such as color, melting point, boiling point, density _________ Properties those which the substance shows as it interacts with, or transforms into, other substances such as flammability, corrosiveness
Physical Properties
__________ properties a property that depends on the amount (mass, volume, etc) that is present
How much of each ingredient is used to make a pancake?
_________ properties a property that is independent of amount (density, temperature, etc)
Properties of Matter
_____________ properties of matter describes its "potential" to undergo some chemical change or reaction by virtue of its composition.
Changes in Matter
When a substance undergoes a physical change, its physical appearance changes.
Ice melts: a solid is converted into a liquid.
Physical changes DO NOT result in a change of ____________.
Changes in Matter
____________ Change:
change that alters the state or appearance of a substance but not it's composition.
Changes in Matter
___________ Change:
change involving a rearrangement of atoms to form different compounds
Sometimes it is difficult to determine whether a change is physical, chemical, or both.
A chemical reaction is usually accompanied by easily observed physical effects, such as the emission of _____________, the formation of a ___________, the evolution of ____, or a ______ change.
Chemical and Physical Properties/Changes
PROBLEM: In each case, decide if each property or change is physical or chemical Physical Chemical
Iron is transformed into rust. The color of sulfur is yellow. The density of uranium is 19.05 g/cm3. Dynamite explodes to form a mixture of gases. Aluminum melts at 933 K. Plants use CO2 from the air to make sugar.
Ener gy: T he a bi l i ty to do _____. Wor k: the a cti on of a for ce thr ough a di sta nce.
Ener gy i s fa mi l i a r to us i n a va r i ety of for ms. el ectr i ca l mecha ni ca l hea t l i ght ________________
We a l so know tha t di ffer ent for ms of ener gy ca n be ______________.
Eg. - a n el ectr i ca l motor conver ts el ectr i ca l ener gy i nto mecha ni ca l ener gy. - a stor a ge ba tter y conver ts chemi ca l ener gy i nto el ectr i ca l ener gy. -stea m engi ne conver ts hea t i nto mecha ni ca l ener gy.
BU T : we a l so know tha t when one ki nd of ener gy i s conver ted i nto a nother , __________________.
T her efor e: T he tota l a mount of ener gy i n the system a t the begi nni ng a nd a t the end i s ________. I n other wor ds: ________________________: ener gy i s nei ther cr ea ted nor destr oyed i n a chemi ca l or physi ca l cha nge.
Potenti a l ener gy: _______ ener gy. Ca n be stor ed i n
________________, or a s the posi ti on of somethi ng r el a ti ve to the center of the ea r th (wa ter behi nd a da m).
Ki neti c ener gy: ener gy of thi ngs i n _______. (a
wa ter fa l l ). M a ny ti mes ki neti c ener gy i s conver ted i nto ther ma l ener wi gy.
Systems th hi gh potenti a l ener gy tend to be _______ a nd wi l l cha nge i n a wa y to l ower the potenti a l ener gy pr esent. M uch of the ener gy i s _________ to the sur r oundi ngs.
D yna mi te ha s hi gh potenti a l ener gy a nd i s ther efor e ________. I t ea si l y r ea cts to for m si mpl er compounds wi th l ess ener gy.
Measurements in Chemistry
_____ defined by length, area and volume _________ the certain quantity of matter _________ to determine how long it takes for a chemical transformation to take place ______________ determines the direction of heat flow
Base Units
Systeme International (SI) (a newer version of the metric system) expresses each fundamental physical quantity in decimally related units
Unit Conversions
We frequently need to convert a measurement from one unit to another (i.e. grams to milligrams) When multiplying numbers we also multiply _____ and when dividing numbers we also divide _____
Magnitude
Expresses units larger or smaller than the base unit
Precision and Accuracy
Precision
A measure of how _______ several measurements are to each other As a general rule: the more _______________ there are, the more precise the measurement
Accuracy
- How close a measurement is to the
_________________________
Significant Figures
The number of digits expressed in a numerical value is call the number of significant figures. "Sig figs" are obtained by ___________ not counting How to determine "sig figs"
Read the number from left to right and count all the digits starting with the first non-zero digit Place a decimal point after the value when its trailing zeros are significant
Significant Figures
Non-zero numbers are always significant. Zeros between non-zero numbers (captive zeros) are always significant. Zeros before the first non-zero digit (leading zeros) are not significant. Zeros at the end of the number containing a decimal point are significant. Zeros at the end of a number without a decimal point are ambiguous
Precision in Calculations
When adding or subtracting, the number of decimal places in the result is the number of decimal places in the number with the ______________. When multiplying or dividing, the number of significant figures in the result is the same as in the quantity with the __________________ ______________. Postpone adjusting result to the correct number of significant figures until a calculation is complete
Rules for Significant Figures in Answers 1. For addition and subtraction. The answer has the same number of decimal places as there are in the measurement with the fewest decimal places. Example: adding two volumes 83.5 mL + 23.28 mL 106.78 mL Example: subtracting two volumes 865.9 mL - 2.8121 mL 863.0879 mL
Rules for Significant Figures in Answers 2. For multiplication and division. The number with the least certainty limits the certainty of the result. Therefore, the answer contains the same number of significant figures as there are in the measurement with the fewest significant figures.
Multiply the following numbers:
9.2 cm x 6.80 cm x 0.3744 cm = 23.4225 cm3
Precision in Calculations Rounding Off of Nonsignificant Figures
If the digit to be dropped which is next to the last sig fig is 5 or greater, add 1 to the last remaining digit. (what is 147.10629 to 6 sig figs?) If the digit to be dropped which is next to the last sig fig is less than 5, leave the last remaining digit as is. (what is 147.10629 to 5 sig figs?)
There are three temperature scales:
Kelvin Scale
Used in science. Same temperature increment as Celsius scale. Lowest temperature possible (absolute zero) is zero Kelvin. Absolute zero: 0 K = 273.15 oC.
Celsius Scale
Also used in science. Water freezes at 0 oC and boils at 100 oC. To convert: K = oC + 273.15.
Fahrenheit Scale
Not generally used in science. Water freezes at 32 oF and boils at 212 oF. To convert:
T(K) = T(C) + 273.15 T (C) = T (K) - 273.15