Chemistry notes

Measurement-significant figures. 1) all non-zero digits are significant. 2) zeros between significant numbers are significant. 3) leading zeros are not signifcant. 4) zeros to the right of a number and to the right of a decimal point are significant. 5) zeros at the end of a number where no decimal is indicated are not significant. 6) zeros to the right of a number and to the imebiate left of a decimal are significant

Measurement-scientific notation. 1)count the number of places from the "decimal point" to the area between the first and second digits 2) the remaining number is the coefficent 3) multiply by 10 raised to the number of digits. Rounding- count the number of digits starting at the first significant number. Look at the number to the right: if 5 or greater round up, if 4 or lower stay the same

Addition and subtraction with significant figures- 1) count the number of significant figures in the decimal portion of each number in the problem. (The digits to the left of the decimal are not used to determine the number of decimal places in the final answer. 2) addition or subtraction in the normal fashion. 3) round the answer to the least number places in the decimal portion of any number in the problem

multiplication and division(all numbers). 1) count the number of significant figures in the decimal portion of each number in the problem. (The digits to the left of the decimal place in the final answer). 2) multiply or divide normal fashion. 3) round answer to the least number of places in the decimal portion of any number in the problem(significant numbers)

density is the ratio of mass to volume. It describes how much "stuff" is i a specific volume.

d=m/v units- grams/mL or kg/L

Example:

what is the density of a block of wood that weighs 

weight

103 mg=g

106 µg=g

109ng=g 

1012 pg=g

103g=Kg

2.21 lb.=Kg

454g =lb

16 oz = lb

2000 lb= ton

Length

1in=2.54cm

10mm=cm

102cm=m

103mm=m

106µm=m

109nm=m

1012pm=m

103m=Km

0.622mi=Km

36in=yd

5280ft=mi

39.37in=m

Volume

1.06qt=L

103mL=L

106µL=L

109nL=L

1012pL=L

4qt=gal

32oz=qt

Time

60sec=min

60min=hr

Dimensional anaylisis

allows you to measure from one land to another( allows you to convert or solve a series of problems in one step. conversion factors are setup by units)

chemistry is the study of the composition of matter

organic chemistry is the study of carbon compounds- living things

inorganic chemistry is the study of non-living things(metals)

physical chemistry is the study of phsical properties

biochemistry is the study of the chemistry of living things and how the compounds effect the body of the organism monipulation of living things

nuclear chemistry is the study of the nucleus

matter is of two things pure substances and mixtures

Pure substance-

A homogeneous sample of matter that has the same composition and distinct properties

Pure substances ae made of elements-

Composed of only one type of atom. Simplist form of matter.

And compounds-

Made of 2 or more elements in defined properties can be seperated into simpler substances by chemical reactions 

Mixtures-

Combination of 2 or more substances each of which retain their own composition and properties 

There are two kinds of mixtures homogeneous-

Contains 2 or more pure substances mixed together (not chemically combined)

And heterogeneous-

Contains 2 or more pure substances mixed un-evenly 

chemical changes involve new substances being formed

inducators of a chemical change

  1. unexpected color change
  2. change in tempature
  3. gas is produced
  4. precipitate is formed (solid product)

there are very few icothermic

temp stays the same

Introduction to solids 

-have definite shape and definite volume 

Water of hydration- water molecules that are an integral part of crystal structure 

Efflorescence- when the atmospheric vapor pressure is lower than the vapor pressure of the hydrate, the water of hydration is lost to the atmosphere

Hygroscopic- absorbing of attracting moisture from the air

Desiccant- a hydroscopic substance used as a drying agent 

Allotropes- the same compound but different chemical properties 

Evaporation- conversion of liquid to a gas below the boiling point of the liquid 

Boiling point- is the temperature at which the vapor pressure of the liquid is the same as the external air pressure 

Viscosity- resistance to flow the stronger the IMF’s, the thicker or more viscous the liquid and the flow is reduced- like molasses, syrup

Surface tension- downward and inward forces that minimize the surface area of a liquid- water beads up on a clean, freshly waxed car. IMF’s create this effect. Surface of a liquid acts as though it has a skin

Atomic Theory

Democritus- matter is made of tiny indivisible particles called atoms 

(Not a theory because there was no experimental evidence)

Dalton

Year of discovery 1802 

  1. All elements are composed of small indestructible particles called atoms
  2. Atoms of the same elements are identical. They are different from all other elements 
  3. When atoms combine, the combine in whole number ratios to make compounds 
  4. During a chemical change, atoms are rearranged to make new compounds 

JJ Thomason 

Year of discovery 1897 

His claim about atoms was that they have electrons (negative) they have an electric current 

He used an experiment where he shot an electric current through a glass tube filled with gas at a low pressure and used the negative side of a magnet to move the electrons 

He came up with the plum-pudding theory of an atom (blueberry) 

 

 

Rutherford –year of discovery 1911

The claim of Rutherford was that atoms are made mostly of empty space and the nucleus is made of positive charges 

  1. Some particles were deflected 
  2. Some particles bounced back 
  3. Most particles went through unchanged

In Rutherford’s experiment he shot alpha particles through gold most of the alpha particles went through the foil but some bounced back and off the foil

Bohr

Year of discovery 1913

His discovery was that electrons where found in different orbital outside the nucleus he experimented with light 

 

He discovered 

  1. Nucleus is in the center of the atom 
  2. Electrons in orbit around the nucleus 

 

 

The Bohr model was the planetary model 

Chadwick discovered the neutrons 

Goldstein discovered the protons

Nuclear chemistry 

Types of radiation 

  • Alpha- this is a helium atom it can be stopped by paper
  • Beta- this is a electron it can be stopped by wood 
  • Gamma- this is a dangerous high energy electro magnetic radiation it can be stopped by concrete (this is an x-ray with an attitude) 

Nuclear that can be emitted or absorbed by a nucleus 

An electrons symbol is β or –ie

A positron is a positive electron

 

Half-life 

Period of time that it takes an isotope to become half its original mass 

  1. Problem that looks for the amount remaining 

Half-life= given

Ao- initial amount= given 

Time= given 

(How many half-lives divide original amount by 2x that many times)

  1. Given initial and final quantity

Fission-splitting of a large nucleus into smaller nuclei of relatively equal size

Fission reactors must control two factors:

  1. Neutron moderation-slow down the neutrons so they can be absorbed by the nucleus.
  2. Neutron absorption-decrease the number of slow moving neutrons-use control rods to absorb neutrons. A meltdown occurs when the control rods are ineffective at slowing reactions and the heat produced can not be removed fast enough 

Fusion-occurs when small nuclei combine to form a nucleus of greater mass 

Detecting radiation-the radiation emitted by radioisotopes is called ionizing radiation. Radiation cannot be detected by the senses so instruments must be used that can detect the ionizing radiation. 

  1. Geiger Counter- primarily detects beta radiation via gas inside a tube in the instrument that gets ionized and can produce a detectable electrical current.
  2. Scintillation Counter- uses specially coated phosphor surface to detect radiation. Ionizing radiation strikes the surface and produces bright flashes of light or scintillation, which are recorded electrically, this counter can detect all types of radiation.
  3. Film Badge- several layers of photographic film that is covered in a light proof paper is worn by people working around radiation. At intervals the paper is developed and the strength and type of radiation exposure can be determined from the darkened film.

We can also use radiation in order to enforce the law by detecting forgeries and analyzing gun powder, and in the farming industry we use it in pesticides and herbicides, and in the medical field it is used to cure or control disease.

 

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