PROPERTIES

& PHASES

OF MATTER

Matter is anything that has mass and takes up space.

Properties of matter describe the characteristics and behavior of matter, including changes.

The soda in the bottle has a mass of 1 kg.

The bus has a large mass of 14000 kg, or 15 tons.

Aspirin and sucrose (table sugar) are both made of carbon, hydrogen, and oxygen, but you wouldn’t use aspirin to sweeten your cereal or take a spoonful of sugar for a headache. Even though sugar and aspirin contain the same elements, differences in their structure determine their individual behaviors.

Salt and water have different composition, so it isn’t surprising that they have different properties. Salt is made up of the elements sodium and chlorine, while water is made up of hydrogen and oxygen. You couldn’t wash your hair with salt and you wouldn’t sprinkle water on your popcorn.

Macroscopic View of MatterYou see a variety of properties of matter everyday.

Iron, for example, is a grey, shiny solid. Iron turns liquid at high temperatures. Iron conducts electricity and is magnetic. Iron is strong, but rusts when exposed to water and air.

Before we start talking about the phases of matter, which you are already familiar with, we need to talk about molecules, and how they move.

Robert Brown, while studying samples of water under the microscope, noted pollen molecules suspended in the water moving

continuously and in irregular directions.

Brown repeated these observations using dye powder in water.

The constant, random motion of tiny chunks of matter is called Brownian Motion.

But do only molecules of water display Brownian Motion? Is all matter in motion?

The Kinetic Theory states that sub microscopic particles of all matter are in constant, random motion. The energy of moving objects is called kinetic energy.

Potential vs. Kinetic Energy

Definition: A physical change is a change in the way something looks or feels. The starting material and the ending material are still the same but look different.

A chemical change is the change of one or more substances into other substances.

• Another name for a chemical change is a chemical reaction.

• Reactants are the starting chemicals in a chemical reaction.

• Products are the new chemicals made in a chemical reaction.

An example of a chemical reaction is when iron reacts with oxygen in air and water to make rust. The reactants are iron, water, and oxygen; the product is rust.

The Phases of Matter

• Solid• Liquid• Gas• Plasma

A solid has definite shape and volume.

Solids have 2 phases: amorphous and crystalline.

Solids are usually hard because their molecules have been packed together. The atoms or molecules of a solid will spin, but not move from their position.

Amorphous solids are solids that have relatively short chains of atoms (tens to hundreds of atoms long). The atom chains move and give the solid the ability to change shape, yet remain solid to the touch. Amorphous solids do not flow.

Crystalline solids are solids that have long chains of atoms (millions of atoms long). The atom chains cannot move, so the solid cannot change shape.

Crystal Lattice

• Appears only in a solid.• Shapes are clearly defined and symmetrical. • Particles are in a 3-D pattern which repeats.

Amorphous Material

• Incomplete crystal lattice• Candles and cotton candy are examples• No defined shape or form

A liquid has definite volume, but takes the shape of the container. Liquids can flow. Liquids are difficult to compress (push the molecules together). The molecules move freely within the bounds of the liquid, though they can escape.

Molecules of a liquid are cohesive, meaning they stick together.

When a solid melts, its crystal lattices disintegrate and particles lose their 3-D pattern. However, when some materials called liquid crystals melt, they lose their

Rigid organization in only one or 2 dimensions. The forces holding the particles together are fairly weak. When the lattices are broken, the crystal can flow like a liquid. Liquid crystal displays (LCDs) are used in watches, thermometer, laptop computers, and calculators because they can melt and solidify with varying electrical charges.

A gas takes the shape and volume of the container. Gases can flow.

The molecules in a gas bounce around, hitting each other and the container they are in. Another word for gas is vapor.

Molecules in solids do not move much and have very little energy.

Liquids move around moderately quickly and have a moderate amount of energy.

Gas molecules move very fast and have a lot of energy.

Solids do not fill their container at all.

Liquids fill the bottom of their container.

Gases fill their container completely.

Plasma is the most common phase of matter in the universe, but the least common found on Earth. Plasmas are gases made of positively and negatively charged atoms and molecules. Examples of plasma include lightening, the gas found in fluorescent light bulbs, the gas found on stars, and the Aurora Borealis (Northern Lights).

Examples of Plasma:

PlasmaMolecules are dissociated into component atoms; electrons move freely among positively charged ions. The plasma state pertains to high energy gas, more relevant to astrophysics than planetary sciences.

SolidAtoms or molecules are held in place, closely packed together; bonds are tight. A solid has a fixed shape and volume.

GasAtoms or molecules move essentially unconstrained. Low density state of matter, having neither fixed volume or shape. A gas will expand to fill the available volume.

LiquidAtoms or molecules remain together, but move relatively easy. A liquid will assume the shape of its container, but has a fixed volume depending upon the temperature.

The process by which matter undergoes phase transitions.

In order to change phases, energy must be added or taken away.

To add energy, you can add heat or decrease pressure (spreads molecules apart).

To take away energy, you can take away heat (cool down) or increase pressure (packs molecules together).

FREEZINGLiquid Solid

As temperature gets colder, molecules move closer together, slow down, and eventually become solid. This happens when pressure increases as well.

MELTING

Solid Liquid

As temperature gets warmer, molecules begin to move around faster and the solid becomes liquid. The same happens when pressure decreases.

Melting Point

• Temperature where a solid becomes a liquid.

• Each substance has their own melting point.

• The melting point of water is 0˚C.

Freezing Point

• Temperature where a liquid becomes a solid.

• Water freezes at 0˚C.

Heat of Fusion

• Energy released when 1 kg of a substance becomes a solid.

• Amount of heat that must be lost when a liquid becomes a solid.

• Joule- unit of energy.

EVAPORATION

&

BOILING

Liquid Gas

As the molecules of a liquid warm up, they move faster and faster, and sometimes break free of the confines of the liquid to become a gas. This happens with decreased pressure, as well.

Boiling Point

• Temperature where a substance goes from liquid to gas.

• Each substance has their own boiling point.• The boiling point of water is 100˚C.

Liquids that evaporate quickly are volatile.

Evaporation is the process by which particles of a liquid form a gas by escaping from the surface of the liquid. The surface area, temperature, and humidity all affect the rate of evaporation.

Heat of Vaporization

• Energy of 1 kg of a liquid when it becomes a gas at its boiling point.

• Amount of heat required to change a substance from a liquid to a gas.

CONDENSATIONGas Liquid

As the molecules of a gas lose heat, they slow down and begin to bump together. If they hit each other without a lot of energy, they may stick together. If enough gas molecules stick together, they form a drop of liquid. This happens with increased pressure, as well.

SUBLIMATION

Solid Gas

The molecules of the solid are so cold that any amount of heat speeds them up sp fast they instantly become a gas, skipping the liquid phase, and escaping the solid.

Ice can sublimate to some extent and become water vapor. Think about what happens when you leave a tray of ice cubes in the freezer for several weeks…the ice cubes shrink. Where does the water vapor go? Onto your food, causing freezer burn, or onto the surface of the freezer, causing ice build-up.

DEPOSITION

Gas Solid

When the molecules of a gas a cooled super-fast, they will slow down to the point where they cannot move, stick together, and become a solid.

The Phase Diagram

Shows the standard curve for the phases of any substance.

As pressure increases or the temperature decreases, the molecules are pushed together and the substance moves towards becoming a solid. As the pressure decreases or the temperature increases, the molecules move farther apart and the substance moves towards becoming a gas.

The triple point is the temperature and pressure at which all three phases of a substance can exist at the same time. This point differs for each substance.

At the left are two phase diagrams for water. On the lower graph we have specified the line for 1 atmosphere, and we can see that the point where this crosses the melting point line is 0ºC (273K), and the point where the 1 atmosphere line crosses the boiling point is 100ºC (373K). Note at the triple point of water, as long as the atmospheric pressure stays low, no matter what the temperature is, water sublimates from a solid to a gas. Remember this for future discussions on the possibility of liquid water on the surface of Mars, where the atmospheric pressure is 0.6% that of Earth's, or roughly 4.56 mm.

The melting curve of ice/water is very special. It has a negative slope due to the fact that when ice melts, the molar volume decreases. Ice actually melts at a lower temperature at higher pressures. (Think of how an ice skater glides along on her skates; the ice momentarily melts due to her weight, and then refreezes when the pressure is released.)

The phase diagram for water.

You must be able to look at a phase diagram and determine a substance’s phase based on given temperature and pressure.

Lets look at some other substances.

A phase diagram for carbon dioxide illustrates the more common forward slope of the melting point line. Notice that the triple point of carbon dioxide is well above 1 atmosphere. Notice also that at 1 atmosphere carbon dioxide can only be the solid or the gas. Liquid carbon dioxide does not exist at 1 atmosphere. Dry ice (solid carbon dioxide) has a temperature of -78.5 degrees F (-61 degrees C, 212 K) at room pressure, which is why you can get a serious burn (actually frostbite) from holding it in your hands. Although carbon dioxide liquid doesn't exist at normal room pressures, it does exist at slightly elevated pressure.

At left is a qualitative phase diagram for nitrogen. Its triple point occurs at an atmospheric pressure of 0.123 and a temperature of 63.15 K. At lower pressures, nitrogen will sublimate. Remember this point when we discuss Triton, a moon of Neptune, towards the end of the quarter. The normal melting and boiling point for nitrogen (that is, at 1 atmos.) is 63.3 and 77.4 K (-320 degrees F!!) respectively. Liquid nitrogen is cold.