CHAPTER 2 SOLIDS, LIQUIDS, & GASES

I. States of Matter - n n A. Solids - have definite volume & definite shape matter can exist in the universe in 4 states or phases - solid, liquid, gas, plasma

1. Particles in a solid - are packed tightly together - stay in fixed positions - shape - are hard to separate

n n In a solid, the molecules are tightly bound together - n n which holds a shape. n n They vibrate in place (Molecular Motion)

2. Types of Solids n n a. Crystalline solids - particles form regular repeating patterns Iron pyrite

- ex.s sugar, salt, sand, snow n n Melting point - the distinct temp. at which a crystalline solid melts. The crystal structure of snow

The molecular structure of salt & a microphotograph of salt crystals.

b. Amorphous Solids n n Particles are not arranged in regular patterns. n n Do not have distinct melting point temperatures (just get softer & softer) n n behave like slow moving, super-cooled liquids

- Can lose their shape under certain conditions Ex.s - plastics, rubber, glass, wax, tar

Wax - an amorphous solid

B. Liquids n n No definite shape but a definite volume - takes on the shape of its container. n n Particles not held as closely together - free to move - flow. (Molecular Motion)

- 100 mL of water = 100 mL in any shaped container. (Definite volume)

n n Liquids do not easily compress or expand. n n Viscosity - (a property of liquids) is the resistance of a liquid to flow n n - honey has a high viscosity compared to water

Is lava liquid? Is it viscous?

C. Gases n n Have no definite shape or volume - volume can change. n n Will fill any available space - a small amount of gas can fill a large volume. n n Will expand without limit.

-Gases can be compressed. A larger amount forced into a smaller space. (A change of volume)

The tanks worn by this diver contain several hours of air. How does this work?

Molecules of a gas are free to move. They move very rapidly and are in constant motion. (Molecular Motion)

This is the Eagle Nebula. Its gas & dust are expanding in space.

What would happen if this balloon had a hole in it? What “limits” the gas?

D. Plasma n n 1. Plasma is - a super-heated, electrically charged gas. n n Plasma is rare on earth. n n Plasma is extremely energetic & dangerous.

Examples of plasma - the sun

Light bulbs & Neon lights

Lightning

Remember - particles of matter always move. (Molecular Motion) n n Solids - particles vibrate in place, tightly bound together n n Liquids - particles are freer, move faster - flow n n Gases - particles even more free, rapid movement n n Plasma - very rapid movement, lots of energy

Temperature affects particle movement. Heat - move faster. Cold - move slower. n n Absolute zero- n n the temp. at which all molecular motion ceases. n n o C n n 0 o Kelvin n n o F

This is dry ice (CO 2 ). What happens to it as the temperature rises? What are its molecules doing?

This is water ice (H 2 O). What happens to it as the temperature rises? What are its molecules doing?

II. Gas BehaviorGas Behavior n n A. Measuring Gases n n 1. - volume can change - gas will fill any available space so will be the same volume as its container n n 2. - temperature is the average energy of motion of the particles of a substance

(3. Temperature) - The faster the particles are moving, the greater their energy and the higher the temperature - A thermometer - a speedometer for molecules! - Gas molecules at 20 o C - travel at 500 meters per second (typically)

4. Pressure n n Gas particles - constantly move & collide with each other & the walls of their containers.

(4. Pressure) n n This results in an outward push by the gas. n n This outward force is called pressure. n n Pressure = Force/Area n n Measured in units of kilopascals(kPa)

Objects like a soccer ball or balloon, have gas under pressure inside that keeps them inflated. This is a pressurized space suit. - What happens if any of these get a hole in them?

4. Relating Pressure & Volume n n Gases behave in predicable ways. n n Robert Boyle - English scientist in the 1600’s - found that when the pressure of a gas is increased at a constant temperature, the volume of the gas decreases. When the pressure decreases, the volume increases.

BOYLE’S LAW

n n Boyle’s Law also applies to situations where volume of a gas changes. n n Then the pressure also changes. What would happen to the pressure & the volume if you squeezed one of these balloons in your hands?

5. Relating Pressure & Temperature n Thought Exercise: n Think of a sand storm. n Would pouring a handful of sand over your arm feel different than being in a strong storm? n HOW?

The greater the speed of the sand particles, the more energy they carry & transfer. n n Gas particles also travel at great speeds. n n Remember: pressure measures how much gas particles push outward on their container. n n - the greater the speed of the gas particles, the greater the pressure. n n - Temp. is the average speed of particles.

Charles’s Law ’s French Scientist Jacques Charles n n When the temperature of a gas at a constant volume is increased, the pressure of the gas increases. n n When the temperature is decreased, the pressure of the gas decreases.

Charles’s Law

III. Graphing Gas Behavior n n Graphs are diagrams that tell how 2 variables or factors are related. n n - graphs can be used to make predictions

Collecting data - use a data table

Data from a data table can then be graphed. This graph shows the linear relationship between temp. & volume which are directly proportional.

This graph shows the relation- ship between pressure & volume which varies inversely.

IV. Changes of State - physical change of matter from one state or phase to another. (ex. solid - liquid)Changes of State n n A. Energy & changes in state n n 1. A substance changes state when its thermal (heat) energy increases or decreases by a sufficient amount. n n 2. Thermal energy - the energy of a substances particles n n - transferred from one substance to another

- always flows from a warmer substance to a cooler substance n n Remember: the arrangement & motion of particles in a substance determine whether substances are solid, liquid, or gas. n n - particles of solids have the least thermal energy, gas the most.

B. Changes of State or PhaseChanges of State or Phase n n 1. MELTING - solid to liquid n n - melting point of a substance is determined by how strongly its particles are attracted. n n - Thermal energy makes molecules vibrate faster. At a certain temperature (the melting point) they can break free.

Melting wax

Melting ice - ice begins to melt at 0 o C, the temperature at which molecules are moving fast enough to flow as a liquid.

Molten silver - What happens to the molecules as the metal cools?

Do substances require the same amount of thermal (heat) energy to melt? THINK of melting: - water ice - steel - plastic - rock

2. Freezing - liquid to solid n n Liquid loses energy as it cools. n n Molecules slow down. n n When water reaches 0 o C, its molecules are moving so slowly that it starts to form into regular patterns - ice crystals n n This is the same temperature at which ice melts!

So what does happen to molten silver molecules as the metal cools?

3. Vaporization - liquid to gas n n Occurs when a liquid gains enough energy to become a gas. n n Two main types: n n - evaporation - molecules on the surface escape n n - ex.s a drying puddle, sweating n n - boiling -takes place inside a n n liquid & on the surface

Note: Evaporation happens at the surface & boiling inside the liquid. Boiling is actually water molecules turning into a bubble of gas inside the liquid & then bubbling out as densities change. Which requires more energy?

- a. boiling point - is the temperature a which a liquid boils n n Boiling points of substances: n n - water (at sea level) = 100 o C n n - salt = 1413 o n n - diamond = 4827 o C n n Boiling point is affected by air pressure. The lower the air pressure, the less energy is needed for molecules to escape. Water will boil at 95 o C in Denver, Colorado.

4. Condensation - gas to liquid n n Occurs when gas particles lose enough energy to become a liquid. n n - ex.s clouds, mist,breath on a mirror n n Steam is NOT condensation (water vapor) but tiny drops of liquid water suspended in the air.

Water vapor condensing on a flower. This happens when the water vapor touches a cooler surface & loses thermal energy. Think of a cold glass on a humid day.

Fog - water vapor cooling & condensing in the rainforest.

5. Sublimation - solid to gas n n Occurs when the surface particles of a solid gain enough energy to become a gas. n n - particles do NOT pass through a liquid state. n n Ex.s - dry ice, naphthalene(moth balls,) iodine, water ice

Dry ice - CO 2 Note that the fog you see is not CO 2 gas, (you can’t see that) - it’s water vapor condensing in the cold surrounding the dry ice.

Dry ice - CO 2 Sublimating - Iodine

Water ice & snow will also sublimate. How could this happen? Hint: It happens in very cold places like Antarctica.

C. Identifying Substances Through Changes of States/Phase n n The properties of substances can help to identify them. n n - boiling/melting points nn nn n n If you were given 3 colorless liquids you could identify them by their boiling & melting points.

Freezing - Boiling Water 0 o o C Ethanol -117 o - 79 o Chloroform - 64 o - 61 o