Chapters 1-4 Flashcards
(51 cards)
1
Q
chemical element
A
pure subtance(a substance with constant composition that can’t be broken down by physical processes) that can’t be decomposed into other substances by ordinary means
2
Q
atom
A
- the smallest particle of an element that cannot be chemically or mechanically divided into smaller particles
- smallest representative unit/particle of an element
- size- 10-10 m and spherical
3
Q
compound
A
- a pure substance that is composed of 2 or more elements linked together in fixed proportions that can be broken down to those elements by some chemical process
- elements combine to form compounds
4
Q
molecule
A
- 2 or more atoms chemically bonded together in characteristic proportions by forces called chemical bonds
- smallest representative unit of a compound
- some elements also exist as molecules (O2)
5
Q
solid
A
- particles are in a fixed pattern
- vibrate
- definite shape and volume
6
Q
liquid
A
- particles are close together
- arranged randomly and free to move
- definite volume
- flows to assume the shape of its container
7
Q
gas
A
- particles are far apart
- move at high speeds
- no definite volume or shape
- expands to fill its container but is also compressible
- can be squeezed into a smaller volume if there is applied pressure and container is rigid
- aka vapor
8
Q
chemical property
A
- a property of a substance that can only be observed by reacting it to form another substance
- Ex: high flammability
9
Q
physical property
A
- property that can be observed without changing the identity of the substance
- don’t change the substance’s identity (ex. density)
10
Q
intensive property
A
- independent of amount of substance present
- pure substances have distinctive properties
- shiny, dull, malleable, hard, colors
- sometimes we use several extensive properties to find an intensive one
- Ex: density
11
Q
extensive properties
A
- dependent on amount present
- Ex: mass, volume, length, width
12
Q
mixture
A
- any matter that is not a pure substance
- a combination of pure substances in variable(not definite) proportions in which the individual substances retain their chemical identities and can be separated from one another by a physical process
13
Q
homogenous mixture
A
- a mixture in which the components are distributed uniformly throughout and have no visible boundaries or regions
- can also be called a solution if it is made of liquids(usually), or they may also be solids or gases
- Ex: sugar water
14
Q
mass
A
the property that defines the quantity of matter in an object
15
Q
matter
A
- anything that has mass and occupies space
- all matter is made up of either pure substances(very few exist in nature) or mixtures
16
Q
substance
A
matter that has a constant composition and cannot be broken down to simpler matter by any physical process; aka pure substance
17
Q
physical process
A
a transformation of a sample of matter, such as a change in its physical state, that does not alter the chemical identity of any substance in the sample
18
Q
determining types of matter
A
19
Q
element
A
- a pure substance that can’t be broken down into simpler substances
- Some elements exist as diatomics in nature
- H2, N2, O2, F2, Cl2, Br2, I2 (H plus the 7 shape)
20
Q
compounds
A
- a pure substance that is composed of 2 or more elements bonded together in fixed proportions and that can be broken down into those elements by a chemical rxn.
- typically have properties very different than those of the elements of which they are composed
21
Q
heterogenous mixture
A
- a mixture in which the components are not distributed uniformly, so that the mixture contains distinct regions of different compositions.
- to identify, you can look for boundaries between the liquids in a liquid mixture OR check that it is not clear/transparent(light can’t pass through such liquids b/c it is scattered by tiny solid particles that are suspended(not dissolved) in the liquid)
- Ex: salad dressing
22
Q
energy
A
the capacity to do work
23
Q
law of constant composition
A
every sample of a particular compound always contains the same elements combined in the same proportions
24
Q
Ion
A
- a particle consisting of 1 or more atoms that has an overall positive or negative electrical charge
- are electrostatically attracted to one another
- may consist of single atoms(Ca2+, Cl-) or can contain 2 or more atoms bonded together
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cation
an ion with a positive charge
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anion
an ion with a negative charge
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Separating Mixtures
* Filters
* separate solid particles from liquid and gas mixtures
* key parameter = pore size(small enough to trap target but not so small that enormous pressure is needed to force adequate air flow
* Using differnces in **volatilities**(how easily they can be converted from liquids to gases)
* distillation
* desalinating seawater b/c water is more volatile
* converting freshwater into distilled(distillation+ion exchange to remove all dissolved ions)
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sublimation
* transformation of solid directly to vapor(gas)
* can happen to snow on a cold, sunny winter day
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Deposition
* when a gas is directly transformed into a solid without ever being a liquid
* when water vapor forms a layer of frost on a cold night
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matter changes
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SI Units
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Significant Figures
* indicate certainty in a measured value
* typically, we use all digits with known certainty plus one uncertain digit
* RULES
* all nonzeros are significant
* leading zeroes are NOT significant
* middle zeroes sre significant
* trailing zeroes
* end in a decimal: significant
* no decimal: ambiguous
* 200 could have 1,2,3
* use scientific notation to remove ambiguity
* exact numbers(12 items/dozen) have infinite sig figs
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Precision
* how well the results of repeated measurements agree with each other
* we can express precision by calculating the average of all the values, finding the standard deviation, and the constructing a confidence interval
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accuracy
* how close the results are to the true value of a quantity
* you can check the accuracy of a balance by taking the mass of objects with known mass
* a thermometer can be calibrated by measuring the temp at which a substance changes state
* periodically analyze control samples that contain known quantities of a substance
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radioactivity
the spontaneous emission of high-energy radiation and particles by materials
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cathode-ray tube(CRT)
* the tube is glass and most of the air has been removed
* Electrodes within the tube are attached to the poles of a high-voltage power supply and the anode is connected to the positive terminal
* electricity passes through the glass tube in the form of a beam of **cathode rays** emitted by the cathode
* ****streams of electrons emitted by the cathode in a partially evacuated tube
* can only be seen in this b/c the end of the CRT is coated with a phosphorescent material
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The Rutherford Model
* JJ Thomson found that cathode ray beams are deflected by magnetic and electric fields
* Direction shows that cathode rays aren't rays of energy, but are just particles with a negative charge
* Using the strengths of two opposing fields, he calculated mass-to-charge ratio of the particles
* this+behavior was always the same no matter what metal is used
* Established existence of electrons
38
Milikan's oil drop experiment
* wanted to measure the charge of an electron so he could determine its mass
high-energy x-rays remove electrons from molecules found in air in the lower of two connected chambers.
* as oil drops fall from the upper chamber into the lower one, they collide with the electrons and pick up their charge
* Milikan measured the mass of the drops in the absence of an electric field(only gravity)
* then, repeated with an electric field so he could make drops fall at different rates and suspend some midair
* Millikan determined that the charge on each drop was a whole-number multiple of a minimum charge (this is the charge on one electron)
39
Thomson's plum pudding model
* the atom is a diffuse sphere of positive charge with negatively charged electrons embedded in the sphere
* like raisins in a plum pudding
* model didn't last long b/c discovery of radioactivity
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radioactivity
* Henri Becquerel originally thought radiation consisted of X-rays
* studied particles emitted by pitchblende(a mineral that is the principal source of uranium) b/c it produces radiation that can be detected on photographic plates.
* found that radiation contains particles and rays(radioactivity)
* **B particles** penetrate solid materials better than **a particles**
* B particles are simply high-energy electrons
* a particles are positively charged(2+) b/c they were deflected in the opposite direction of B particles
* a particles are more than 103 times as big as B
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Hans Geiger and Ernest Marsden's gold foil experiment
* disproved Thomson's plum-pudding model
* bombarded a thin gold foil with a beam of a particles emitted from a radioactive source
* if plum pudding was correct, most a particles would pass through the diffuse positive spheres of gold atoms, but a few would interact with the electrons(the raisins) and be slightly deflected.
* What really happened:
* 1 in every 8000 particles was deflected through the foil at an angle of 90˚
* Very few (1 in 100,000) bounced back in the direction the particles came(crazy)
* So....plum pudding can't account for large angles of deflection
* these deflections occurred b/c the a particles occasionally encountered small, yet massive, regions of highly positive charge
* An atom consists of a massive, but tiny, positively charged **nucleus** surrounded by a diffuse cloud of negatively charged electrons.
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nucleus
* the positively charged center of an atom that contains nearly all the atom's mass
* **nucleon**
* either a proton or a neutron in a nucleus
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proton
a positively charged subatomic particle present in the nucles of an atom
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neutron
an electrically neutral(uncharged) subatomic particle found in the nucles of an atom
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atomic mass unit(amu)
* unit used to express the relative masses of atoms and subatomic particles; it is exactly 1/12 the mass of one atom of Carbon with six protons and six neutrons in its nucles
* equal to a dalton(Da)
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properties of subatomic particles
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isotopes
* atoms of an element containing different numbers of neutrons
* Z is the same, but diff #neutrons
* A = mass # = #protons + #neutrons
* Z = atomic number = #protons
* X = symbol
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systematic errors
* when several attempts are all off by a set factor
* Ex: a scale is always 1 lb too high
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random errors
caused by a faulty instrument/experimenter
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