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

• Big # = positive exponent.

• Small # = negative exponent.

• Base x +Power moves decimal place to the right.

• Final # is bigger than the base.

• Base x -Power moves the decimal place to the left.

• Final # is smaller than the base.

Chemicals

Pure Substance

Cannot be separated by physical means.

Mixture

Can be broken down into parts.

Homogenous

Same look all the way through.

Brass

Heterogenous

Visibly different.

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.

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.

• 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

The point where liquid and gas coexist in a supercritical fluid.

Supercritical Fluid

A phase where liquid and gas coexist.

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.