theory test 1

States of Matter

Solid, Liquid, Gas.

Changes in States of Matter

Depend on kinetic activity of molecules; increased temperature increases molecular motion causing state changes.

Effect of Temperature on Molecules

Temperature ↑ → molecules move faster → collisions increase → molecules move farther apart → change of state.

Melting (Solid → Liquid)

Heat causes molecules in a solid to expand and become liquid.

Evaporation (Liquid → Gas)

Heat absorbed by liquid molecules allows them to become gas.

Kelvin Scale

International temperature scale; K = 273 + °C

Celsius Scale

Centigrade system; °C = K − 273; °C = 5/9(F − 32).

Fahrenheit Scale

Used mainly in hospitals; F = (9/5 × °C) + 32.

Kinetic Activity

Motion of molecules.

Absolute Zero

Temperature where molecular kinetic activity ceases.

Melting Point

Temperature where solid becomes liquid.

Boiling Point

Temperature where liquid becomes gas at atmospheric pressure.

Sublimation

Solid → Gas without becoming liquid.

Evaporation

Liquid molecules escape into gas below boiling point.

Vapor Pressure

Pressure from molecules hitting liquid surface and escaping.

Critical Temperature

Temperature above which a gas cannot be liquefied at any pressure.

Gas Molecular Characteristics

Small molecules in constant random motion; collisions are elastic.

Effect of Temperature on Kinetic Activity

Kinetic activity increases directly with temperature.

Atmospheric Pressure

Pressure exerted by air on Earth.

Pressure Equivalents

1 atm = 760 mmHg = 14.7 psi = 33.93 ft H₂O.

Gas Pressure Measurement

Mercury barometer; aneroid barometer.

mmHg → cmH₂O

1 mmHg = 1.36 cmH₂O.

psi → cmH₂O

1 psi = 70.34 cmH₂O.

Heat Capacity

Calories needed to raise 1 g by 1°C or 1 lb by 1°F.

Conduction

Heat transfer in solids.

Convection

Heat transfer in liquids and gases.

Radiant Heat

Heat transfer without direct contact.

Vaporization

Liquid → Gas; requires heat energy.

Evaporation example

Liquid → Gas.

Condensation

Gas → Liquid.

Absolute Humidity

Actual water vapor content in gas.

Relative Humidity

Actual water vapor / capacity × 100.

Effect of Temperature on Humidity

Warm air holds more water.

Warm air holds more water.

Force exerted by like molecules at liquid surface.

Cohesion

Attraction between like molecules.

Adhesion

Attraction between unlike molecules.

LaPlace's Law

P = 2 × ST / r.

Avogadro's Law

Equal volumes of gas at same pressure & temperature contain same number of molecules.

Avogadro's Number

6.023 × 10²³ molecules per gram molecular weight.

Gram Molecular Weight Volume

1 gmw occupies 22.4 L.

Molecular Weight of Oxygen

32 g/mol.

Boyle's Law

Pressure ∝ 1/Volume (temperature constant).

Charles's Law

Volume ∝ Temperature (pressure constant).

Gay-Lussac's Law

Pressure ∝ Temperature (volume constant).

Dalton's Law

Total pressure = sum of partial pressures.

Combined Gas Law

(P₁V₁)/T₁ = (P₂V₂)/T₂.

Nitrogen (N₂)

78.084%; 593.43 mmHg.

Oxygen (O₂)

20.95%; 159.22 mmHg

Argon (Ar)

0.934%; 7.09 mmHg.

Carbon Dioxide (CO₂)

0.0314%; 0.23 mmHg.

Water Vapor Pressure & Temperature

PH₂O depends on gas temperature.

PH₂O in Lungs

47 mmHg at 37°C (always saturated).

STPD / BTPS / ATPS

Standardized reference conditions for gas calculations.

Diffusion

Movement from high → low concentration.

Graham's Law

Diffusion ∝ 1 / √density.

Henry's Law

Gas dissolved in liquid ∝ partial pressure.