Midterm Flashcards
What are the states of matter?
Solid, Liquid, Gas
Liquid
no definite shape, but have a definite volume, able to flow
Solids
definite shape and volume not compressible
Gas
no definite shape or volume, molecules very far apart
Elements
the simplest type of substance with unique physical and chemical properties. Consist of only 1 atom that cannot be broken down into simpler substances by chemical or physical means
Compounds
a structure that consists of two or more atoms that are chemically bound together thus behaves as an independent unit
heterogeneous
consists of two or more phases of variable composition that differ in properties (ie. oil floating in water)
Homogeneous
has the same properties and composition throughout the sample. (ie. saltwater to brine is a homogeneous aqueous solution)
Who created the periodic table?
Dmitri Mendeleev
physical properties
properties measured without changing the chemical composition of the substance
Chemical properties
substances potential to react with some other substances in its enviornment
mass
measure of the amount of matter in a sample
Volume
measure the amount of space the matter takes up
Density
the ratio of an object’s mass to its volume
Weight
based on gravity
All non zero numbers are (BLANK)
significant
Zeros in between digits or numbers are (BLANK)
significant
Trading zeros are significant when there is a decimal (BLANK) them
before (ie. 505.400 has 4 sig figs)
Leading zeros are (BLANK)
not significant
Hoe many sig figs. are in 0.00751
3
Zeros at the end of digits, when their is no decimal point are (BLANK)
ambigious
10000 has how many sig. figs.
1
672001 has how many sig. figs.
6
For addition, subtraction, multiplication and division. your answer should have (BLANK) number of decimal points
fewest (ie. 7.821- 2.1 = 5.7)
When using sig. figs in math round (BLANK)
the final answer
accuracy
how close a measurement is to the real value
precision
reproducibility or how close the measurements are to each other
What is Aristotle’s theory on matter and atoms?
proposed an continuous model of matter without atoms
The law of conservation of mass
mass is neither created nor destroyed in a chemical reaction but merely changes form
law of definite proportions
a compound is always made up of the same relative masses of elements that composed it.
What does forensic science deal with
the application of science to legal matters and crime solving
which of the following states of matter is generally considered the most ordered?
solid
copper sulfate, CuSO4, is sometimes used to create the blue color in toilet water. Copper sulfate is an example of what?
a compound
Pure substances
have a uniform composition and cannot be separated by physical methods
The mobile phase in thin-layer chromatography is often
a liquid such as water
to whom does credit for the creation of the periodic table go?
Dmitri Mendeleev
Which element uses the symbol Na
Sodium
What atomic symbol corresponds to iron
Fe
Which of the following atomic symbols represents the coinage metals, copper, silver, and gold.
Cu, Ag and Au
Which of the following elements are metals?
Iron, lead, calcium
In the case study described in Chap 1 why didn’t Agent Rawalt believe the Mexican government’s claim about the death of the informant?
The color of the soil from the bodies didn’t match the color of the soil from the ranch they were supposedly found
Which of the following measures how much matter is contained in a simple?
Mass
What is the difference between mass and weight
Weight is a measure of the pull of matter to the earth, while mass is a measure of how much matter is in a sample
How many sig. figs. are there in the number 0.00204
3
How many sig. figs. does 23.120 have
5
Good accuracy and good precision in three measurements means that all three have what in common
value close to each other and close to the true value
When a material floats in water, what is its density
less than 1.0 g/mL
What 2 measurements determine density, and in what relationship to each other?
mass divided by volume
What is the density of a material with a mass of 23.9g and a volume of 27.5 mL
0.869 g/mL
How did Pitera’s shovel provide evidence of his burying bodies?
The shovel still had soil on it specific t the burial site
DNA evidence cannot be used to identify remains in a funerary urn, for what reason?
Cremation destroys all DNA
The continuous model of matter, postulated by Aristotle, believed in what is the smallest material
nothing was; matter should be able to be divided over and over.
The law of conservation mass states
mass is neither created nor destroyed in a chemical reaction, but merely changes form.
What is the mass of the missing material in the following equation? (BLANK) g carbonic acid (22.0g CO2 + 9.0 g H2O)
31.0 g
According to Daltons Atomic Theory, how do atoms combine?
in whole number ratios
The compounds NO and NO2 represent which of the postulates of Daltons’ atomic theory?
Atoms combine in simple, whole number ratios to form compounds
Which sub-atomic particle has a positive charge
proton
Rutherford’s gold foil experiment proved what the matter?
That it has regions of dense, positive charge.
How are two samples of an element referred to when they possess differing numbers of neutrons?
as isotopes
What is the ground state of an atom
the state in which all electrons are in the lowest possible energy level.
An electron that has been pushed into a higher energy level is said to be in what state?
an excited state
What is the orbital of an electron?
the region of space with the highest probability of finding the electron
An s orbital has what shape
spherical
How could forensic chemists tell if a sample from the inside of a funerary urn was cement instead of human ashes?
The percentage of silicon was much higher in cement (about 19%) than in human ashes (about 1%)
