Chapter 3 ALCOS 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.

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.