chem exam1

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Laws

concise verbal or mathematical statement of a relationship b/w phenomena that is always the same under the same condition. Ex. Newtowns second law of motion, force = mass times acceleration.

Theory

is a unifying principle that explains a body of facts and/or those laws that are based on them. Hypotheses that survive many experimental tests of their validity may evolve into theories. Are always constantly tested. Ex. Big bang theory.

Scientific Method

a systemic approach to research. Problem/question, Observation/research, Formulate a hypothesis, Experiment, Collect & Analyze results, Conclusion, Communicate the results

Matter

anything that occupies space and has mass

States

Solid: has both definite shape & a definite volume. The particles that make up a solid are very close together and many times are restricted to a very regular framework called a crystal lattice. Liquid: has a definite volume but no definite shape. It conforms to the shape of its container. The particles are moving much more that in the solid. They are usually clumps of particles moving relatively freely among other clumps. Gas: has neither a definite shape nor volume. It expands to fill its container. The particles are far apart, moving rapidly with respect to each other, and act independently of each other.

Extensive property

measurable value depends on how much matter is being considered. Examples: Mass, which is the quantity of matter in a given sample of a substance, is an extensive property. Volume, defined as length cubed, is another extensive property. Length, The value of an extensive quantity depends on the amount of matter.

Intensive property

measurable value does not depend on how much matter is being considered. Examples: Density, defined as the mass of an object divided by its volume, is an intensive property. Temperature, Color, Unlike mass, length, and volume, temperature and other intensive properties are not additive.

The boiling point of water on the Kelvin is

373K

Room temperature on the Kelvin, Celsius and Fahrenheit

298K, 25C, 77F

Scientific notation

is used to express very large & very small numbers.

1.234 kg

4 significant figures

606 m

3 significant figures

0.08 L

1 significant figure

2.0 mg

2 significant figures

0.00420 g

3 significant figures

8 oz

1 cup

16 oz

1 pint

32oz

1 quart

32 oz

0.946 L

128oz

1 gal

1 lb

454 grams

2.2 lb

1 kg

1 gal

3.784L

1cm3

1mL=1cc

1hr

3600seconds

1 inch

2.54 cm exactly

1mi

5280ft

1qt

0.946L

1cc

1cm3 = 1mL exactly

Democritus

The Greek philosopher postulated the existence of the atom.

Dalton 4 hypothesis he proposed to describe the nature of matter

Elements are composed of extremely small particles called atoms; All atoms of a given element are identical, having the same size, mass, & chemical properties. The atoms of one element are different from the other elements; Compounds are composed of atoms of more than one element. In any compound the ratio of the #s of atoms of any two of the elements present is either an integer or a simple fraction; A chemical reaction involves only the separation, combination, or rearrangement of atoms; it does not result in their creation or destruction.

The law of definite proportions was presented by

Joseph Proust.

What was the significance of Rutherford's experiments

He discovered the nucleus (not the neutron); By the gold foil method, measuring the scattering of alpha particles. Most of the particles passed through the gold foil w/little or no deflection. A few were deflected at wide angles. And occasionally, bounced back.; Quoted: "it was as incredible as if you had fired a 15-in shell at a piece of tissue paper and it came back and hit you"

How did this change the model of the atom proposed by Thompson

Rutherford reasoned that if Thomson's model was correct then the mass of the atom was spread out throughout the atom. Then, if he shot high velocity alpha particles (helium nuclei) at an atom then there would be very little to deflect the alpha particles. He decided to test this with a thin film of gold atoms. As expected, most alpha particles went right through the gold foil but to his amazement a few alpha particles rebounded almost directly backwards; These deflections were not consistent with Thomson's model. Rutherford was forced to discard the Plum Pudding model and reasoned that the only way the alpha particles could be deflected backwards was if most of the mass in an atom was concentrated in a nucleus. He thus developed the planetary model of the atom which put all the protons in the nucleus and the electrons orbited around the nucleus like planets around the sun.

Proton (+1)

mass: 1.673 x 10-24

Electron (-1)

1.675 x 10-24

Neutron (0)

9.109 x 10-28

The nucleus is the dense central core of the atom. What subatomic particles are contained within the nucleus?

Proton + neutron

Atomic Number (Z)

Number of Protons

Atomic Number

Number of Protons, Number of Electrons

Number of Neutrons

Mass Number (A) - Atomic Number

group I

Alkali (+)

group II

Alkaline Earth metals (+)

group 6A

(-) Other non-metals

group 7A

(-) Halogens

Group 8A

(-) Noble gases

Radioactivity

spontaneous emission of particles and/or radiation

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