Seven basic SI units
the meter (m), the kilogram (kg), the second (s), the kelvin (K), the ampere (A), the mole (mol), and the candela (cd).
significant figures (sig figs)
In order to determine the number of significant digits in a value, start with the first measured value at the left and count the number of digits through the last digit written on the right. For example, the measured value 36.7cm has three digits, or sign
express numbers in scientific notation
To write a number in scientific notation: Put the decimal after the first digit and drop the zeroes. To find the exponent count the number of places from the decimal to the end of the number.
dimensional analysis
a technique of problem-solving that uses the units that are part of a measurement to help solve the problem
error
the difference between the experimental value and the accepted value
Difference between error and mistake
An error is an action which is inaccurate or incorrect. In some usages, an error is synonymous with a mistake. In statistics, "error" refers to the difference between the value which has been computed and the correct value.
Differences between determinate error and indeterminate error
Systematic Error (determinate error) The error is reproducible and can be discovered and corrected. Random Error (indeterminate error) Caused by uncontrollable variables, which can not be defined/eliminated. ... Personal errors - occur where measurements
Ways to avoid determinate error and indeterminate error
Random errors: Take more data. Random errors can be evaluated through statistical analysis and can be reduced by averaging over a large number of observations.
Systematic errors: difficult to detect and cannot be analyzed statistically, because all of the
Precision vs. Accuracy
Precision:
- immunity to variation (hits the same spot every time)
- wider Confidence Interval = less precise study
Accuracy: immunity to systematic error or bias
- dart hits center
Calculate absolute error
To calculate the absolute error, use the formula, "Absolute Error = Measured Value - Actual Value." Begin by plugging the actual value into the formula, which will either be given to you or is the standardly accepted value. Then, make a measurement and pu
Calculate percent relative error
|accepted value - experimental value| \ accepted value x 100%
Define and calculate density.
Density is the measurement of how much mass of a substance is contained in a given volume, it is calculated by dividing the mass by the volume.
Determine the number of valence electrons in an atom
For neutral atoms, the number of valence electrons is equal to the atom's main group number. The main group number for an element can be found from its column on the periodic table. For example, carbon is in group 4 and has 4 valence electrons. Oxygen is
Write Lewis symbols for each of the following elements: phosphorus, flourine, boron (#11)
P (5 dots/electrons), F (7 dots), B (3 dots)
Identify the number of bonded pairs and non bonded electron pairs in a given Lewis structure
By knowing the structure of the compound you can easily identify the bond pair and lone pairs in a compound. For example in NH3 there are three H attached to the central atom N and there is an extra pair of electrons which have not taken part in bonding,
Use molecular shape and electronegativity to determine if a molecule is polar or nonpolar
The molecule's polarity will be determined on the negative and positive regions on the outer atoms in the molecule. Differences in electronegativity between two atoms can cause the polarization of the bond that connects them, but the overall polarity of a
physical properties
A characteristic of a pure substance that can be observed without changing it into another substance (appearance, texture, color, odor, melting point, boiling point, density, solubility, polarity)
Solution
A homogeneous mixture of two or more substances
Solute
A substance that is dissolved in a solution.
Solvent
A liquid substance capable of dissolving other substances
precipitate
A solid that forms from a solution during a chemical reaction.
saturated solution
a solution that cannot dissolve any more solute under the given conditions
unsaturated solution
A solution that contains less solute than a saturated solution does and that is able to dissolve additional solute
supersaturated solution
contains more dissolved solute than a saturated solution at the same temperature
Evaporation
The change of a substance from a liquid to a gas
Filtration
a technique that uses a porous barrier to separate a solid from a liquid
Recrystallization
The process by which bonds between atoms in minerals break and re-form in new ways during metamorphism.
Identify circumstances in which one desperation technique is better to use than another
...
mass percent formula
mass of solute/mass of solution x 100
beaker tongs
Used to move beakers containing hot liquids
Crucible Tongs
to hold hot crucibles
Why is a repeated heat-cool-weigh cycle important
because the results change every time and with this cycle comes closer to the actual result since all of the residue is finally gone