Victor 7th Grade - Phases of Matter

• Matter is...
• made up of particles called atoms
• the arrangement of these particles determines the state of matter, either solid, liquid, or gas.
• Matter can change between states when the temperature or pressure is changed
• phase changes are physical changes, NOT chemical changes.

• Solids...
• in a solid, the particles are in a fixed position relative to one another.  They cannot move very much.
• Solids have a definite shape and a definite volume.
• They can vibrate but they stay in the same relative position.
• If the particles are arranged in a regular sequence, a crystal results.  Salts are examples of crystals.

• Liquids...
• have a fixed or definite volume but take the shape of the container they are put in.
• the particles move relative to one another (they flow) but still stay close together.
• the particles can move around each other but not far apart from each other.
• liquids only exist for a limited (small) temperature range.  Water is only a liquid between 0 and 100 degrees celcius.

• Gas...
• Gases have no definite shape or volume.  They will expand or contract to fill all available space.
• particles in a gas are free to move independently from each other.
• the particles move freely and rapidly, and in no particular direction.

• Phase changes...
• a phase change is a physical change
• phase changes require the additional or removal of heat energy to the substance.
• there are four (4) phases of matter: solid, liquid, gas, and plasma.
• you must add heat energy to go from a solid to a gas, therefore a gas has more energy than a solid.
• melting is the process of adding heat energy to a substance and going from the solid phase to the liquid phase.
• vaporization is the process of adding heat energy and going from the liquid phase to the gas phase.  There are two (2) different types of vaporization:
• Evaporation: takes place at the surface of the liquid ONLY.
• Boiling: takes place throughout the liquid.

• Phase change...
• condensation is the process of removing heat energy from a substance and going from the gas phase to the liquid phase.
• freezing is the process of removing heat energy from a substance and going from the liquid phase to the solid phase.
• sublimation is the process of adding heat energy to a substance and going from the solid phase DIRECTLY to the gas phase without ever becoming a liquid.  Dry ice is the most common example of a substance that undergoes sublimation.

• Air temperature is usually measured in units called degrees (Celsius ^.C or Farenheit ^.F)
• Pure water freezes at degrees Celsius
• Pur water boils at^.100 degrees Celsius
• Heat is transfered in three (3) ways...
• radiation
• convection
• conduction

Earth absorbing solar energy

The upper movement of warm air and the downward movement of cool air form convection currents.

Thermal energy

Temperature is the average amount of energy of motion in the molecules of substance.

A thermometer is a thin glass tube with a bulb on one end that contains a liquid, usually mercury or colored alcohol.

Heat is the energy transferred from a hotter object to a cooler one.

Conduction is the direct trasfer of heat from one substance to another substance that it is touching.

Convection is the transfer of heat by the movement of a fluid.

• The three phases of matter are...
• solid
• liquid
• gas

Heat is need to change from phase to phase.

When matter becomes a solid its molecules slow down.

The temperature of liquid nitrogen is -196 degrees Celsius.

When molecules completely stop moving it is called Absolute Zero.

Scientists have come to within a few billionths of a degree above absolute zero.

Carbon dioxide gas is put into Coke to make it fizz.

Yes, a solid has a definite shape and a definite vollume.

Solid particles cannot move around they are packed together. They do have some thermal energy which allows the particles to vibrate. They are not compressible.

A liquid does not have a definite shape.  Liquids assume the shape of their containers.  Liquids have a fixed and definite volume.

Liquid particles move around slowly. Liquids are compressible.

Gas has no definite shape and no definite volume.

Gas particles move around very quickly. Gases are compressible.

Thermal energy is energy that comes from heat.

A change in phase always occurs with a change of heat.  Heat which is energy, either comes into the material during a change of phase or heat comes out of the material during this change.  (Although the heat content of the material changes, the temperature does not.)

Sublimation is the transition of a substance directly from the solid phase to the gas phase without passing through a liquid phase.

Deposition is the change of state directly from gas to solid (such as the formation of frost in the winter).

When a solid changes to a liquid, MELTING occurs.

When liquid changes to a gas, vaporization occurs.

When a solid goes directly to a gas, sublimation occurs.

When a gas changes to a liquid, condensation occurs.

When a liquid changes to a solid, freezing occurs.

In a solid, the particles are touching, and the only motion allowed to them is vibration.  (Particles in a solid are held together by forces which depend on the actual substance... ionic bonds, convalent bonds, metallic bonds, hydrogen bonds).

In a liquid are mainly touching, but some gaps have appeared in the structure.  These gaps allow the particles to move. The particles are arranged randomly. They are still touching and are still close together.

In a gas, the particles are entirely free to move around.

Temperature is a measure of the average kinetic energy of the idividual particles of an object.

Thermal energy is the energy of a substances particles.  (Thermal energy comes from heat)

Heat is a high temperature to a low temperature. (It is the quality of being hot)

• Heat is transferred through....
• conduction
• convection
• radiation

Conduction is the transfer of heat from one molecule to another through a substance.

Convection is the method of heat transfer within fluids (water).  It cannot take place in solids.

An example of convection is a pot of water being heated on the stove top.

A convection current is the continuous movements of water caused by the expansion of the water as its temperature rises.

Radiation is energy that comes from a source and travels through space and may be able to penetrate various materials.   Light, radio, and microwaves are types of radiation that are called non-ionizing.

• Conduction is heat transfer between part of the same material or different material which are adjacent to one another.
• Convection is heat transfer from one material to another via a medium, such as air or water.
• Radiation is heat transfer without any medium and through electromagnetic waves such as between Sun and Earth.

Heat moves from a warmer object to a cooler object.

Heat will flow from one substance to another until the two substances have the same temperature.

A change of state is the physical change of a material (solid, liquid, gas) to another form (solid, liquid, gas)

Matter changes from one state to another by heating the matter or cooling the matter.

An increase in thermal energy give particles more kinetic energy, which causes them to vibrate more.  As they vibrate more, the volume they take up increases.  For example, when ice water is heated up, the molecules spread out, take up greater space, and so the result is liquid (water).

Thermal expansion is the tendency of matter to change in volume in response to a change in temperature.

When a substance is heated, the particles begin moving more and usually maintain a greater distance of separation.

A heat engine uses energy provided in the form of heat to do work and then exhausts the heat which cannot be used to do work.

• Heat engine examples include:
• heat pump
• refrigerator

• It is difficult to measure the volume of a gas because...
• 1. gases have not definite volume (they take on the volume of the container they are in)
• 2. gases are compressable
• 3. gases are invisible

Pressure and temperature affect the volume of a gas.

Robert Boyle was an 17th century Irish chemist, physicist, and inventor.

He studied chemistry and combustion.

Boyle's Law stated that the volume of gas varies inversly with pressure.

• If pressure is down, volume is up.
• If pressure is up, volume is down.

We use psi as the units for pressure.

We use mL or m³ for units of volume.

We use the following formula to calculate Boyle's Law:

P_i x V_i = P₂ x V₂

• Thermal Energy increases when:
• ice melts
• the glass of water you left in your bedroom disappears
• Dry ice disappears

• Thermal Energy decreases when:
• Water droplets form on your mirror in the bathroom when you take a shower.
• You make popsicles from apple juice.

If temperature rises, substances expand.  Decreasing temperatures cause substances to contract.

Jacque Charles was a french scientist/physicist who studied oxygen, nitrogen, and hydrogen.

He developed a law of volume that describes how gases expand when heated.

When temperature goes up, volume goes up. When temperature goes down, volume goes down.

• We use the following formula to calculate Charle's Law:
• V_i / T_i = V_f / T_f

• Vi = initial volume
• Ti = initial absolute temperature
• Vf = final volume
• Tf = final absolute temperatature