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28 Cards in this Set

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Element:
implest form of matter with unique physical and chemical properties.
An element consists of only one kind of atom.
Pure substance:
matter whose composition is fixed.
Each element is unique because the properties of its atoms are unique.
Molecule:
independent structural unit consisting of two or more atoms chemically bonded together.
Compounds:
two or more different elements that are chemically bound together.
-elements are present in fixed parts by mass (chemical formula)
-the properties are different from those of its component elements
Mixtures:
groups of two or more substances (elements and/or compounds) that are physically intermingled.
-components of a mixture can vary in their parts by mass
-mixtures retain many of the properties of its components.
-can be separated by physical means
Law of Conservation of Mass:
-mass cant be created or destroyed
-the total mass of substance doesn’t change during chemical reactions
-the number of substances can change but the total amount of mass doesn’t
Law of Definite (or constant) Composition:
-no matter what its source, a particular compound is composed of the same elements in the same parts (fractions) by mass.
Fraction by mass:
is that part of the compound’s mass contributed by the element.
Law of Multiple Proportions:
If elements A and B react to form two compounds, the different masses of B that combine with a fixed mass of A can be expressed as a ratio of small whole numbers.
Kinetic Molecular Theory:
Gas volume changes greatly with pressure
Solids/Liquids resist significant changes in volume
Kinetic Molecular Theory contin:
Gas volume changes greatly with temperature
50 to 100 times greater than it does for solids or liquids
Gas have relatively low viscosity
Gases flow much more freely than solids or liquids
Most gases have relatively low densities

Gases are miscible.
Air: 18 different gases mixed together
Liquids are not always miscible
Water and alcohol are miscible
Water and gasoline are nonmiscible
Pressure:
force applied over area P=F/A
Liquids:
have a combination of these attributes that changes continually a region that is orderly, one moment becomes random the next, and vice versa.
Surface Tension:
the energy required to increase the surface area by a unit amount, units of J/m2
Surfactants:
(surface-active agents)
Soaps, petroleum recovery agents and biological fat emulsifiers, decrease the surface tension of water by congregating at the surface and disrupting the hydrogen bonds.
Viscosity:
its resistance to flow, viscosity decreases with heating
Crystalline Solid:
well defined repeating patterns
-because their atoms, molecules, or ions occur in an orderly arrangement
Amorphous Solid:
have poorly defined shapes because of their lack of long range ordering throughout the samples.
solid to liquid
0 degrees (boiling and freezing point)
the stronger the bonds the stronger the melting points
high melting point- strong bonds
reforming strong bonds in hard. strong bonds are ionic (wrist grabbing example)


molecular bonds are week bonds (pinky example)

the stronger the bond the more KE is needed.
Crystal Lattice and the Unit Cell:
-the lattice consists of all points with identical surroundings
-the arrangements of the particle points defines the lattice
Unit Cell:
the smallest portion of the crystal that is repeated in all three directions.
The Coordination Number:
the number of the nearest neighbors surround it.

There are 7 crystal systems!
Simple Cubic Unit Cell:
the centers of the eight identical particles defines the corners of the cube.
Coordination Number= 6
Body-Center Cubic Unit:
identical particles lie at each corner and the center of the cube.
-those at the corners don’t touch each other
-however, they all touch the center.
Coordination Number= 8
Face-Centered Cubic Unit:
identical particles lie at each corner in the center of each face but not in the center of the cube.
Coordination Number=12
Packing efficiency and the creation of the unit cells:
the higher the coordination number of the crystal, the greater the number of particles in a given volume (3-D space)
Amorphous Solids:
non crystalline solids
-somewhat ordered regions connected by large disordered regions.
allotropes:
(carbon)

same element (substance) different forms. Solids only.