UNIT 1 Matter and Energy UNIT 1 Matter and Energy Chapter 3-Matter

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. Gas Gas – neither definite volume nor definite shape; particles are at great distances from one another Liquid Liquid – definite volume but indefinite shape; particles close together but not in fixed positions Solid Solid – 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 matter Each substance has a unique set of physical and chemical properties. Physical Properties are measured without changing the substance. e.g., color, density, odor, melting point Chemical 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-Practice DIRECTIONS: Classify each of the following properties as either physical or chemical. 1.Blue color 2.Density 3.Flammability 4.Solubility 5.Reacts with acid to form hydrogen gas 6.Supports combustion 7.Sour taste 8.Melting point 9.Reacts with water to form a gas 10.Hardness

Using Properties of Matter Separation techniques exploit the differences in properties of matter 1.Filtration - remove solid from liquid 2.Distillation - boil off one or more components of a mixture 3.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 CuSO 4 ) Can be classified as reversible and irreversible Which of the above would be reversible/irreversible?

Changes of Matter CHEMICAL 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 change 2.Formation of a gas 3.Formation of a solid 4.Formation of an odor 5.Heat/light released/absorbed 6.Change in pH

Changes of Matter DIRECTIONS: 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 ENERGY

Energy Energy 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 = J

Changes in Energy Energy 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 Thermodynamics Systems 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 Energy Although 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 difference What 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

Thermochemistry A 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 J of heat energy to raise the temperature of 1 g water by 1 o C; adding the same amount of heat to the same mass of gold raises the temperature of gold by 32.4 o C WHY??? 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 1 o C Each substance has its own specific specific heat

Specific Heat Problems The 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 31.7 o C to 69.2 o C? The specific heat of phosphorus tetrachloride is J/g o C. To solve this, you must use 5-step problem solving! q

Specific Heat 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 31.7 o C to 69.2 o C? The specific heat of phosphorus tetrachloride is J/g o C. Step 1. m = 96.7 gc p = J/g o C T 1 = 31.7 o C T 2 = 69.2 o C q = ? Step 2. q = mc p (T 2 -T 1 ) Step 3. q = (96.7 g)(0.874 J/g o C)(69.2 o C o C) Step 4 and 5. q = 3169 J

Phase Changes Phase 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 energy Phase 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 heat Both occur at the same temperature called the melting point or the freezing point 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 heat Both 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 Changes Energy 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 Changes Latent 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.