Chem 121 terms
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What is chemistry?
The study of matter.
Rules for sig figs (5)
- 1. Nonzero are always sig figs
- 2. Zeroes at beginning are never sig
- 3. Zeroes between non zero are always
- 4. Zeroes at the end of a number with decimal are always sig
- 5. Zeroes at the end of a number with no decimal points may or may not be sig depending on exactness of the number.
Quantity of matter in an object.
What are the three states of matter?
Solid,liquid and gas
What s density?
Mass per unit volume
Comparison of density with that of water.
Capacity to do work
Energy of motion-any moving object
Stored energy-drawn bow, water held bavk by dam
Amount of heat necessary to raise 1 gram of a substance by 1°C
A form of energy, measured in calories
Units are multiplied and divided while crossing out unit labels. For conversions.
Testing of hypotheses and theories by collecting facts.
Substances are used up and others formed.
Substances do not change their identity.
Fixed composition, cannot be further purified
Combination of two or more pure substances
Pure substances can be (2):
- Elements-cannot be subdivided by physical or chemical means
- Compounds-elements united in fixed ratios
Mixtures can be (2):
- Homogeneous matter-uniform composition throughout
- Heterogeneous matter-nonuniform composition
The smallest particle that retains the chemical properties of the element. The interaction among atoms accounts for the properties of matter.
Dalton's atomic theory (5)
- All matter is made up of tiny, indivisible particles called atoms
- All atoms of a given element have the same chemical properties.
- In ordinary chemical reactions, no atom of any element disappears or is changed into another element.
- Compounds are formed by the chemical combination of two or more different kinds of atoms. In a given compound, the relstive numbers of each type of atom are constant and most commonly expressed as integers.
- A molecule is a tightly bound combination of two or more atoms that act as a single unit.
- Evidence for dalton's theory-
- Antoine lavoisier discovered the law of conservation of mass-no matter can be eier created or destroyed.
Law of constant composition-any compound is always made up of elements in the same proportion by mass.
Monotomic, diatomic and polyatomic elements
How many atoms cling together-helium and neon are monatomic, oxygen contains two atoms in each molecule.
Diatomic molecules (7):
- Free atoms do not exist
- O2 oxygen
- H2 hydrogen
- N2 nitrogen
- F2 fluorine
- Cl2 chlorine
- Br2 bromine
- I2 iodine
- O3 ozone
- P4 phosphorus (one form)
- S8 sulfur ( one form)
- Diamond-millions of carbon atoms
Z-number of protons in the nucleus
- Atomic mass unit-relative scale of masses of atoms
- 1 amu is 1/12 the mass of a carbon atom containing 6 protons and 6 neutrons
Particles and charges
- Proton +1
- Electron -1
- Neutron neutral
Sum of the number of protons and neutrons in its nucleus. Electrons are so small they dont count
Determined by different number of neutrons. Has different mass number.
Weighted average of the masses in amu of its isotopes found on earth. The weight is very close to its mass number because protons and neutrons have an approx mass of 1 amu
Invented periodic table. Started by arranging elements in order of increasing atomic weight. He noted that certain properties occur periodically.
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