Chapter 3ALCOS 7

Solid, Liquids, and Gases

Section 1: States of Matter• Solids

– Definite volume and definite shape– Particles are packed tightly together in fixed

positions

• 2 Forms of Solids– Crystalline & Amorphous

• 1. Crystalline Solids– Solids that have particles arranged in a

regular, repeating pattern.– Made up of crystals

• 2. Amorphous Solids– The particles are not arranged in a regular

pattern

Liquids• Particles are free to move in a container but

remain in closer contact with one another.• Does not have a definite shape, but it does

have a definite volume.• Particles move around more freely than the

particles in a solid.• Viscosity

– The resistance of a liquid to flowing• Fluid

– Substance that flows

• Surface Tension– The surface of water can act like a sort of skin

due to this property of liquids.– The result of an inward pull among the

molecules of a liquid that brings the molecules on the surface closer together.

Gases• Particles can spread apart and fill all the

spaces available to them.• Undergoes changes in volume most easily.• Does not have a definite shape or a defnite

volume.

Section 2 Changes in State• Changes between a Solid & a Liquid

– Melting and Freezing• Melting

– Change from a solid to a liquid– The characteristic temp. at which a pure solid

changes to a liquid is its melting point!– Melting Point of Pure Water – O degrees C

• Freezing– Change in state from a liquid to a solid (reverse

of melting!)– Pg. 78– The freezing point of water is the same as its

melting point. O degrees Celcius

Changes Between Liquid & Gas• Vaporization

– A liquid becomes a gas• 2 Types

– 1) Evaporation 2)Boiling• Evaporation

– Vaporization that takes place only on the surface of a liquid.

– Ex. A shrinking puddle.

• Boiling– Liquid to gas- BELOW the surface as well as at

the surface• Boiling Point

– Temp at which a liquid boils.– 100 degrees C– The boiling point of a substance is affected by

the pressure of the air above the substance– The lower the pressure, the less energy needed

for the particles of the liquid to escape into the air.

• Condensation– The opposite of vaporization– Occurs when particles in a gas lose enough

thermal energy to form a liquid. – Ex. Clouds typically form when water vapor in

the atmosphere condenses into liquid droplets. When the droplets get heavy enough, they fall to the ground as rain.

• An uncovered pot of soup is simmering on a stove, and there are water droplets on the wall above the back of the stove. What sequence can you infer has occurred?

• A. melting, then boiling• B. freezing, then thawing• C. condensation, then vaporization• D. vaporization, then condensation

• DDDDDDDDDDDD!!!!!

Changes Between Solid & Gas• Sublimation

– A SOLID turns directly into a GAS!!!– Pieces of dry ice (solid carbon dioxide) becomes

smaller through this process. – Page. 81 Dry Ice

• In cold climates, the amount of snow on the ground may decrease even if the temperature stays below zero degrees Celsius. The process that best explains this is SUBLIMATION!!

Section 3 – Gas Behavior• Measuring Gas

– When working with a gas, it is helpful to know its volume, temperature, and pressure.

• Volume– Amount of space that a gas takes up– Cm3, mL, and L– Volume of a gas is the same as the volume of its

container because gas particles move and fill the space available.

– Weather balloons are filled with only a small amount of helium because the VOLUME of the balloon will increase as the air pressure decreases at higher altitudes.

• Temperature– Particles within any substance are always

moving.– Measure of the average energy of random

motion of the particles of a substance. – Faster the particles move, the greater their

energy and the higher the temperature.– The average speed of gas is very fast.

• Pressure– The force of a gas’s outward push divided by the

area of the walls of the container– Measured in pascals (Pa) or kilopascals (kPa)– Pressure = force / area– The GREATER the SPEED of gas particles in a

container the GREATER the PRESSURE!

Boyle’s Law• Robert Boyle in 1600s• Boyle found that when the pressure of a gas

increases at constant temperature, its volume will DECREASE.

• When the pressure is decreased, the volume increases.

• To test Boyle’s law, you could change the volume of a gas and measure its PRESSURE at constant TEMPERATURE.

• Shows relationship between volume and density of a gas.

• The graph of Boyle’s law shows that as the volume of a gas at constant temp. is changed, its pressure varies INVERSELY with the volume.

• A graph that shows that the pressure of a gas varies inversely with its volume demonstrates?– Boyle’s Law!!!!

Charles’s Law• Jacques Charles- 1700s• Interested in Balloons• When the temperature of a gas is increased

at a constant pressure, its volume increases.• When the temperature of a gas is decreased

at constant pressure, its volume decreases.

• According to Charles’s Law:• When the temperature of a gas decreases

at constant volume is pressure decreases. • When the temperature of a gas increases at

constant volume, its pressure increases.

• When an inflated balloon is exposed to cold air, the volume of the balloon decreases.

• When the temperature of a gas in a balloon increases, the volume of the balloon will increase.

http://www.youtube.com/watch?v=kKs1bZKxGgc

Charles’s Law Graph• A graph that shows that the volume of a gas

is directly proportional to its temperature under constant pressure.

• Shows the relationship between TEMPERATURE and VOLUME of gas.

• When a graph of two variables shows a straight line passing through the point (0,0) the two variables are DIRECTLY proportional to each other.

Thermal Energy• When a substance cools, it looses thermal

energy to its surroundings.• The temperature of a substance increases

when the THERMAL energy of the substance increases.