UNIT 1 Matter and Energy

Chapter 3-Matter

MATTER

CLASSIFICATION OF MATTER

All matter can be classified according to its phase and its composition

Phases of Matter

Plasma – high temperature, ionized phase of matter as found on the sun.

GasGas – neither definite volume nor definite shape; particles are at great distances from one another

LiquidLiquid – definite volume but indefinite shape; particles close together but not in fixed positions

SolidSolid – definite volume and shape; particles packed in fixed positions

All matter can be classified into 4 phases (physical states)

The amount of internal thermal energy (heat) determines the state of matter.

Composition of Matter

Property – any characteristic that allows us to recognize a particular type of matter and to distinguish it from other types of matterEach substance has a unique set of physical and chemical properties.Physical Properties are measured without changing the substance.

e.g., color, density, odor, melting pointChemical Properties describe how substances react or change to form different substances

e.g., rusting, sodium reacts with water, radioactive decay, lack of reactivity

Properties of Matter

Properties of Matter-PracticeDIRECTIONS: Classify each of the following propertiesas either physical or chemical.

1. Blue color2. Density3. Flammability4. Solubility5. Reacts with acid to form hydrogen gas6. Supports combustion7. Sour taste8. Melting point9. Reacts with water to form a gas10.Hardness

Using Properties of MatterSeparation techniques exploit the differences in properties of matter

1. Filtration - remove solid from liquid2. Distillation - boil off one or more components of

a mixture3. Chromatography - exploit the solubility of

components

Changes of Matter***Both physical and chemical changes are ALWAYS

accompanied by a transfer of energy***

PHYSICAL CHANGE - changes in the physical properties of matter

Properties of a material change but the composition remains the same

Changes of Matter

3 basic categories» Change of state (e.g. melting, freezing, condensing, sublimation, etc.)» Mechanical change (e.g., ripping, chopping, breaking, cutting, etc.)» Dissolving a solute into a solvent (e.g., forming a solution from CuSO4)

Can be classified as reversible and irreversible Which of the above would be reversible/irreversible?

Changes of MatterCHEMICAL CHANGE-one or more substances transforms into one or

more chemically different substances

Composition of matter ALWAYS changes (i.e., change in identity)

Created by chemical reactions

Changes of Matter

Indicators of a chemical reaction:1. Color change2. Formation of a gas3. Formation of a solid 4. Formation of an odor5. Heat/light released/absorbed6. Change in pH

Changes of MatterDIRECTIONS: Classify each of the following examples as a physical or chemical change.

1. Sodium hydroxide dissolves in water.2. Hydrochloric acid reacts with sodium hydroxide to produce a salt, water, and heat.3. A pellet of sodium is sliced in two.4. Water is heated and turned to steam.5. Potassium chlorate decomposes to potassium chloride and oxygen gas.6. Iron rusts.7. Ice melts.8. Acid on limestone produces carbon dioxide gas.9. Milk sours.10. Wood rots.

ENERGY

EnergyEnergy makes changes in matter possible. We use it to do things for us. It moves cars along the road and boats over the water. It bakes a cake in the oven and keeps ice frozen in the freezer. It plays our favorite songs on the radio and lights our homes. Energy is needed for our bodies to grow and it allows our minds to think.

Scientists define energy as the ability to do work.Modern civilization is possible because we have learned how to change energy from one form to another and use it to do work for us and to live more comfortably.

Units of energy: joule (J) and calorie (cal)1 calorie = 4.184 J

Changes in EnergyEnergy transforms during changes in matter.

e.g., Chemical energy is converted to thermal energy when we burn wood in a fireplace or burn gasoline in a car's engine

2nd Law of ThermodynamicsSystems in nature tend to go from higher energy to lower energy.

e.g., - warm objects have more energy than cold objects; energy flows from warm to cold until there is no temperature difference

- many chemical reactions occur because the energy of the matter involved is lower after the reaction than before

Changes in EnergyAlthough energy transforms during changes in matter, the total amount of energy never changes.

e.g., Hot coffee transfers energy to its surroundings (the room, your hand, etc.) until there is no longer a temperature differenceWhat happens to the energy in the hot coffee as it cools?

The energy lost by the coffee cup is exactly EQUAL to the energy gained by the room.

1st Law of Thermodynamics“Law of Conservation of Energy” Energy can never be created or destroyed, just converted from one form to another.

Thermochemistry

The motion of molecules can be increased/decreased by adding/removing energy to/from a substance.

Specifically, the study of the changes in heat energy that accompany changes in matter is referred to as thermochemistry.

Changes in heat energy can be: exothermic or endothermic

ThermochemistryA calorimeter is used to measure the energy given off or absorbed during physical and chemical changes.

Thermochemistry

The same amount of heat causes a different change in temperature in different materials.

e.g., It takes 4.184 J of heat energy to raise the temperature of 1 g water by 1oC;

adding the same amount of heat to the same mass of gold raises the temperature of gold by 32.4oCWHY??? Different materials have different abilities to store thermal energy (heat).

Specific Heat - the quantity of heat energy needed to raise the temperature of 1g of a material by 1oC

• Each substance has its own specific specific heat

Specific Heat ProblemsThe amount of heat energy transferred can be calculated using the following relationship:

PROBLEM: Phosphorus tetrachloride is a compound used in the manufacture of pesticides and gasoline additives. How much heat is required to raise the temperature of 96.7 g of this chemical from 31.7oC to 69.2oC? The specific heat of phosphorus tetrachloride is 0.874 J/goC.

To solve this, you must use 5-step problem solving!

q

Specific HeatPROBLEM: Phosphorus tetrachloride is a compound used in the manufacture of pesticides and gasoline additives. How much heat is required to raise the temperature of 96.7 g of this chemical from 31.7oC to 69.2oC? The specific heat of phosphorus tetrachloride is 0.874 J/goC.

Step 1. m = 96.7 g cp = 0.874 J/goC T1 = 31.7oC T2 = 69.2oC q = ?

Step 2. q = mcp(T2-T1)Step 3. q = (96.7 g)(0.874 J/goC)(69.2oC -

31.7oC)Step 4 and 5. q = 3169 J

Phase ChangesPhase Change - transition when a solid, liquid or gas changes from one phase to another due to the increased/decreased motion of molecules Phase changes often occur due to the absorption or release of heat energyPhase changes come from the competition between temperature and attractive intermolecular forces

• Intermolecular forces tend to attract molecules together into rigid structures

• As the amount of thermal energy increases in a substance, this rigid structure is disrupted

SOLID - LIQUID• melting - (solid to liquid) - increased molecular motion due to absorbed heat• freezing - (liquid to solid) decreased molecular motion due to released heatBoth occur at the same temperature called the melting point or the freezing point

Phase Changes

Phase Changes

LIQUID - GAS• vaporization (boiling/evaporating) - (liquid to gas) - increased molecular motion due to absorbed heat• condensation - (gas to liquid) decreased molecular motion due to released heatBoth occur at the same temperature called the boiling point or the condensation point

Phase Changes

SOLID - GAS• sublimation - (solid to gas) - increased molecular motion due to absorbed heat• deposition - (gas to solid) decreased molecular motion due to released heat

Phase ChangesEnergy can be absorbed or released by changes in temperature and during phase changes.During a phase change, no temperature change is noticeable since the heat energy goes into or comes out of the internal potential energy of the molecules.

Phase ChangesLatent Heat - thermal energy which is absorbed or released by a phase change

• Heat of fusion - the amount of energy needed to change 1 g of material from solid to liquid (or vice versa)• Heat of vaporization - the amount of energy needed to change 1 g of material from liquid to gas (or vice versa)

The heat of vaporization is much greater than the heat of fusion because breaking bonds between atoms or molecules takes much more energy than exchanging bonds.