Unit Two Flashcards
Precision
How close a series of measurements are to each other
Precise = consistent
Percent error
A measure of accuracy, the difference between the experimental value and the accepted value
Percent error = |experimental - accepted| / accepted x 100
Significant figures
The number of significant digits
Sig fig rules
- Nonzero numbers are always significant (117 = 3 sig figs)
- Zeroes between nonzero numbers are always significant (10017 = 5 sig figs)
- Zeroes at the end of a number are only significant if there is a decimal point present (117.00 = 5 sig figs, 11700 = 3 sig figs)
- Zeroes at the beginning of a number are NOT significant (00.117 = 3 sig figs)
Adding and subtracting sig figs
Calculate the answer and then round to the last decimal place that all of the given values had in common that was significant
17.1 - 1.17 = 15.9
Multiplying and dividing sig figs
Determine which given value has the lowest number of sig figs and then calculate your answer and round to that number of sig figs
117 x 1.1700000 = 137
When taking measurements in the lab, you are allowed to estimate…
1 digit
Accuracy
How close a measurement is to the accepted value
Accurate = correct
Length
Meter
m
Mass
Kilogram
kg
Time
Second
s
Temperature
Kelvin
K
Volume
Liter
L
Amount of substance
Mole
mol
Million
Mega
M
Thousand
Kilo
k
Tenth
Deci
d
Hundredth
Centi
c
Thousandth
Milli
m
Millionth
Micro
μ
Billionth
Nano
n
Trillionth
Pico
p
Order of prefixes?
M_ _ KHDBDCM_ μ _ n
Temperature can be measured in…
Fahrenheit
Celsius
Kelvin (most used in science)
Celsius and Kelvin equation
K = °C + 273
Fahrenheit and Celsius equation
°F = 1.8°C + 32
Scientific notation
Used to make really big or really small numbers easier to deal with
X * 10^y
Dimensional analysis
Units or labels are factored out top to bottom
Dimensional analysis rules
- Identify starting and ending units
- Start with the given and line up conversion factors
- Multiply all top numbers and divide by each bottom number
- Check answer and units
Group/family
Vertical column
Period
Horizontal row
Metals
Most elements, shiny, ductile, good conductors of electricity and heat, generally solid at room temperature, high density, malleable, high melting point, tend to gain electrons
Nonmetals
Poor conductors of heat and electricity, low density, usually gases at room temperature, brittle and dull looking, tend to lose electrons
Metalloids
Have properties of both metals and non metals (hybrids)
Alkali Metals
Group one Highly reactive Low melting and boiling points Ductile and malleable One electron in outermost shell Good conductors of heat and electricity Explode in water Lose valence electrons to their elements Form a +1 ion Group 1 (except hydrogen) 1 valence electron Soft metals--usually exist in compounds Highly reactive--react violently with water Form +1 ions
Alkaline earth metals
Group 2 Shin low densities, melting and boiling points Silvery-white Somewhat reactive 2 valence electrons Reactive metals (slightly less than Group 1) Mineral ions like Mg2+ important in body 2 valence electrons Form +2 ions
Halogens
Highly reactive Electronegativity All three states of matter 7 valence electrons Low melting and boiling points In elemental form, are toxic and can produce salts Can't be found in nature Group 17 Most reactive nonmetals Found in nature as diatomic elements Readily combine with metals to form salts
Noble gases
Colorless Odorless Low chemical reactivity Monatomic Valence is full--8 in outer shell except helium Nonflammable Oxidation #0--doesn't form compounds easily Conduct electricity Group 18 Gases Unreactive (8 valence electrons) Called noble gases because they don't react
Transition metals
Good conductors Malleable High melting point (except mercury) Solid at room temperature High density Colorful when in a compound
Lanthanides and actinides (rare earth metals)
Silver, silvery-white, or gray High luster, tarnish in air High electrical conductivity Have common properties Naturally occur together in minerals Found with nonmetals in 3+ oxidation state Make up inner transition metals
