Terminology
- Volatility
- More easily evaporated.
Significant Figures
- All trailing zeroes following decimals are significant.
- Leading zeroes are non-significant regardless if they exist before of after the decimal place.
- Otherwise, all leading and trailing zeroes are non-significant.
Rounding Significant Figures
- Find the right digit to remove to round.
- .5 rounds down!. .5## where numbers are not 0 round up!.
- When performing arithmetic, your answer cannot have more sig fig than either original #.
- Multi-step operation = don't round until the very end.
Scientific Notation
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Big # = positive exponent.
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Small # = negative exponent.
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Base x +Power moves decimal place to the right.
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Final # is bigger than the base.
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Base x -Power moves the decimal place to the left.
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Final # is smaller than the base.
Chemicals
- Pure Substance
- Cannot be separated by physical means.
- Mixture
- Can be broken down into parts.
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- Homogenous
- Same look all the way through.
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Brass
- Heterogenous
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Spaghetti
Differentiating Characteristics
Good ones are specific and intensive (doesn't change).
Extensive characteristics such as mass are bad because they may change.
- Density
- Mass/volume
- Energy?
- Amount of energy exchanged per unit of mass.
- Phase Transitions
- A popular differentiating characteristic.
- Uses temp at which material changes phase, measured at 1 atm.
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- Boiling Point
- The temperature at which liquid changes to gas or vice versa.
- The substance is a gas when temps are higher than the boiling point.
- The substance is a liquid when temps are lower than the boiling point.
- Melting Point
- The temperature at which solid changes to liquid or vice versa.
Phase Transitions
- Deposition
- Gas to solid.
- Sublimation
- Solid to gas.
- Vaporization
- Liquid to gas.
- Condensation
- Gas to liquid.
- Freezing
- Liquid to solid.
- Melting
- Solid to liquid.
Temperature Scales
- Kelvin
- The zero point signifies the lowest theoretical temperature.
- K = C + 273.15
- Celsius
- The zero point signifies the freezing point of water.
- K = C + 273.15
Cooling Curves
Describes phase transitions. x-axis is time. y-axis is temp. The decreasing slopes represent phase states. The horizontal lines represent the phase transition processes. As time increases and temp decreases, the system releases energy.
- Tb
- The boiling point.
- Represents the point where liquid/gas phase change occurs.
- Tm
- The melting point.
- Represents the point where liquid/solid phase change occurs.
Energy Relations
- System
- The thing that's acted upon.
- Surroundings
- The external environment.
- Energy
- Ability to do work or cause changes in a system.
- Measured in Joules = energy needed to apply 1 newton of force over 1 meter.
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- 1 J = 1 N/m
- Energy Absorbed
- Energy that is absorbed into the system from the surroundings.
- Melting/vaporization/sublimation.
- Energy Released
- Energy that is released from the system into the surroundings.
- Freezing/condensation/deposition.
Phase Diagrams
Temp of phase change is dependant on external pressure.
x-axis is temp. y-axis is pressure. As pressure increases, so does the temperature needed to transition.
- Triple Point
- All three phases coexist.
- Critical Point
- Liquid and gas coexist in a supercritical fluid.
Vapor Pressure Curves
Tells us the vapor pressure of liquids at different temperatures.
- Vapor Pressure
- The pressure a vapor exerts on the air at the surface at which it evaporates.
Separation Techniques
- Filtration
- Uses a physical barrier to separate solids from a mixture.
- Crystallization
- Induces liquid to solid by altering solubility based on temp/concentration.
- Distillation
- Separates liquid from gas based on boiling points.