Mr. Bouyer 6th Grade Science
Day 1 | Day 2 | Day 3 | Day 4 | Lab | Vocabulary Test

Solid Liquid Gas Plasma Thermal expansion Phase change Melting Freezing	Sublimation Snow Vaporization Evaporation Condensation Freexing point Melting point	Boiling point Crystal Amorphous Metastable Fluid Viscosity STP Gas Law

Matter is known to exist in 4 phases
or
Wait is it 5 phases ?:
Solid
Liquid
Gas
Plasma

Then what is the difference between water and ice? You might use something like "definite shape" or "takes the shape of it's container" to describe the difference. While this distinction is certainly correct, it does not address the difference in the structure of the particles of matter.

To understand the "real" difference in the phases of matter, you must understand the difference in the energy of the phases. Energy is found inside matter. You can think of this energy as the motion of the particles making up the matter. As the energy increases inside matter, the particles move faster and faster. An increase in particle motion causes most matter to expand and a decrease in particle motion causes most matter to contract. This characteristic of matter is called thermal expansion.

Defining states of matter according to particle motion:

Solid particles have the least amount of energy. Their motion is so weak that the particle cannot push other particles out of the way. Because of this the particles of a solid are packed close together and the motion seems to be a vibration.

Liquid particles have enough energy to push other particles out of the way. When the particles of a liquid bump into each other, they push the particles farther apart and move past them. This causes the "flow" of a liquid.

Gas particles have a high amount of energy. The particles collide with enough force to push the particles so far apart that they escape the attraction of the surrounding particles. Gas particles have the most energy of any "regular" phase of matter. These particles will naturally move from an area of high concentration to an area of low concentration, diffusion.

Plasma particles have extremely large amounts of energy. The collisions in a plasma are so violent that electrons are knocked away from their atoms. Plasma can be thought of as a gas consisting of positive ions and electrons instead of atoms.

Phase change: The physical change of matter from one phase to another. A phase change takes place because the particles of a substance gain or lose energy, causing them to change their motion.

Names for the possible phase changes:
Melting - solid changes to liquid
Freezing - liquid changes to solid
Sublimation - solid changes to gas
Snow gas changes to solid
Vaporization - liquid changes to gas
• Evaporation - vaporization that takes place at the surface of a liquid.
Condensation - gas to liquid



Every pure substance has a:

Freezing point temperature - the temperature at which a liquid changes to a solid. Water freezes at 0 oC, 32 oF Table salt freezes at 801 oC Diamond freezes at 3700 oC Freezing point depression - the addition of a nonvolatile solute makes the solution freeze at a lower temperature than the pure solvent. The change in freezing point depends only on the concentration of the solute particles, not on the composition of the solute.

Melting point temperature - the temperature at which a solid changes to a liquid. Water (ice) melts at 0 oC, 32 oF Table salt melts at 801 oC Diamond melts at 3700 oC

Boiling point temperature - the temperature at which a liquid boils. Water boils at 100 oC, 212 oF Table salt boils at 1413 oC Diamond boils at 4200 oC Boiling point elevation - the presence of nonvolatile solute particles in a solvent causes the boiling point of a solution to be raised. The addition of these particles means a higher tempeature is needed to change phase. The change in boiling point depends only on the concentration of the solute particles, not on the composition of the solute.

Test Your Concept Understanding: The most common element in the universe is hydrogen and the most common phase of matter in the universe is plasma. Why are each very hard to find on earth? The reason is not the same for both.

Day 2

What type of substance is glass?

Types of solids:
Additional information about solids from chemistry class.

1. Crystalline - The particles are arranged in a regular, repeating pattern. Crystalline solids are true solids and tend to hold their shape. The shape of the crystal is determined by the bond angle between the particles. Many natural minerals have crystalline shapes.

   Crystallographer

   Basic crystal shapes: cubic - there are 3 axes, all of equal length. hexagonal - there are 4 axes, 3 of equal length and 1 longer. tetragonal - there are 3 axes, 2 of equal length and 1 longer. orthorhombic - there are 3 axes, all of unequal length.

2. Amorphous - The particles have no regular pattern. These substances exhibit characteristics that are usually associated with solids, such as rigidity, hardness, and elasticity. However, amorphous substances have no crystalline form. Amorphous substances can be thought of as supercooled liquids. The application of an external force over a period of time causes these materials to flow and become permanently deformed.

   Substances that occur in a long-lasting amorphous form are said to be metastable.

Fluid - any substance that flows. Liquids and gases are fluids.

Viscosity - the resistance of a fluid to flow.

• Water has a low viscosity.
• Honey has a high viscosity.

Activity:

• As a group (your table), ask your science facilitator for material to do the following. Make each model as sturdy as you can so that it will hold its shape.

Follow these steps to construct a cubic crystal model. Cut 4 straws into thirds. Use thin wire to connect the 12 pieces into a cubic form. Follow these steps to construct a tetragonal crystal model. Cut 4 straws in half. Take four of the halves and cut each of them in half again. Use thin wire to connect the 8 shorter pieces into the two square ends. Wire the 4 long straws to the ends to complete the tetragonal form. Follow these steps to construct a orthorhombic crystal model. Cut 4 straws in half. Take 4 of the halves and cut off 1/3 of the length. Use thin wire to connect two of the short pieces and two of the medium length pieces into a rectangle to make one end. Repeat this to make the other end. Wire the 4 long straws to the ends to complete the orthorhombic crystal model.

Day 3

Why does the volume of a gas increase when it is heated?

Gas volume is changed by temperature and pressure. The distance between the particles of a gas will change as the temperature and pressure change. Because of this, you must know the temperature and pressure at which a gas volume is measured.

Standard Temperature and Pressure - "STP"

"Standard Temperature" is 0^o Celcius.
• All calculations involving gas temperature must use Kelvin temperature.
• K = C^o + 273
• Notice it is K - not ^oK
• You say "Kelvins" - not "Degrees Kelvin"

"Standard Pressure" is 1 atmosphere (at sea-level)

• Pressure can be defined as an amount of force exerted per unit of area.
• Pressure can be expressed in units of atmospheres, millimeters of mercury, or kiloPascals.
• 1 atm = 760 mm Hg = 101 kPa
• mm Hg is millimeters of mercury. This describes the height of a vertical column of mercury that the pressure will support against gravity.
• kPa is kiloPascals. A Pascal is a unit of force equal to one Newton per square meter. It is describing the pressure exerted by the molecules of the gas striking a surface.

Gas Laws: Used to describe the characteristics of a gas as conditions change.
Additional gas law information from chemistry class.

Boyle's Law - used when pressure changes.

• The volume of a fixed amount of gas varies inversely with the pressure of the gas.
• As pressure increases, volume decreases.
• As pressure decreases, volume increases.

  The equation for Boyle's Law is:

  

Charles' Law - used when temperature changes.

• The volume of a fixed amount of gas varies directly with the temperature of the gas.
• As temperature increases, volume increases.
• As temperature decreases, volume decreases.

  The equation for Charles' Law is:

  

Homework Assignment 043:
This assignment must be turned in by the beginning of class tomorrow to receive credit.
Scoring criteria

1. Convert the following temperatures:
   1. 273 ^oC to K
   2. 1500 K to ^oC
   3. 100 ^oC to K
   4. 500 K to ^oC
2. A sample of gas has a volume of 9 liters at 1 atmosphere of pressure. What is its volume when the pressure is increased to 3 atmospheres?
3. Two liters of water vapor are collected from boiling water. If the temperature is increased to 127 ^oC, what will be the volume of this sample of water vapor?
4. In the real world, both temperature and pressure usually change when working with a gas. How would you calculate a new volume if both temperature and pressure change?

Day 4

Is normal atmospheric pressure in Red Rock, Oklahoma more or less than "standard" atmospheric pressure?

The Combined Gas Law: a combination of Boyle's law and Charles' law.

The equation for the Combined Gas Law is:

Combined Gas Law Practice Problems: A gas occupies 750 ml at STP. What will be its volume at 500 mm Hg and 300 K?   The pressure on 100 cm3 of gas increases from 1 atm to 2 atm while the temperature drops from 20 oC to -10 oC. What is the new volume?

In-class Assignment 044:
This assignment must be turned in by the end of class today to receive credit.
Scoring criteria

Use the combined gas law to work the following problems:

1. A gas volume of 250 cm³ is measured at 760 mm Hg and 25 ^oC. What will be the new volume when conditions are changed to 800 mm Hg and 20 ^oC?
2. The volume of a gas at STP is 1550 liters. What will be the new gas volume if the temperature is increased by 75 K and the pressure is decreased by 50 kPa?

Plasma is a gas consisting of positive ions and electrons instead of atoms.
This phase of matter usually occurs at such high temperatures that the particle collisions are so violent they break electrons away from atoms.

Glass is an amorphous substance.
Antique window glass has been shown to be thicker at the bottom than at the top, indicating that glass will flow downward over a long period of time. This fits with the idea of glass being a "supercooled" liquid.

Heating a gas increases the speed of the molecules. This causes the collisions between the molecules to become more violent, pushing the farther apart - increasing the volume of the gas.
While most substances will expand when heated, the amount of increase is much larger in gases than in any other phase of matter.

Normal atmospheric pressure at Red Rock, Oklahoma is less than the "standard".
Standard atmospheric pressure is measured at sea-level. Red Rock, Oklahoma is about 800 feet above sea-level, meaning that there is less air above us here than at sea-level.