Matter and Energy Zumdahl Chapter 3 Grand Prismatic Spring in Yellowstone National Park Source: David Maisel/Stone/Getty Images Why does soda fizz when you open the bottle? Universe Classified Matter is the part of the universe that has mass and volume Energy is the part of the universe that has the ability to do work Chemistry is the study of matter The properties of different types of matter The way matter behaves when influenced by other matter and/or energy 3.1 Matter AIMS -learn about matter and its three states What is matter?? Aristotle’s View….not science, but logic. Matter What is Matter??? Anything that has mass and occupies a volume “Matter is the real substance of which actual physical objects - the 'things' of this world - are composed.” Sir Roger Penrose. Can also be thought of as being composed of protons, neutrons, and electrons (more on that later) All Matter exists in one of 4 Physical States Gaseous-no definite shape or volume Liquid-definite volume, but not shape Solid-definite shape and volume Plasma-like gases, but atoms are made up of free electrons and ions of the element. Figure 3.1: Liquid water takes the shape of its container. Some Characteristics of Gases, Liquids and Solids and the Microscopic Explanation for the Behavior gas liquid solid assumes the shape assumes the shape of the retains a fixed volume and volume of its part of the container and shape container which it occupies rigid - particles locked particles can move particles can move/slide into place past one another past one another compressible lots of free space between particles not easily compressible little free space between particles flows easily particles can move past one another flows easily particles can move/slide past one another not easily compressible little free space between particles does not flow easily rigid - particles cannot move/slide past one another Examples of substances and their commonly found state Solid Ice cube, diamond, iron bar, rock Liquid Gasoline, water, alcohol, blood Air, helium, oxygen, natural gas Gas What determines the Physical State of a particular substance? Temperature Melting point or boiling point of substance What causes a substance to change into another Physical State? Addition of energy -melting -boiling Subtraction of Energy -freezing -condensing (condensation) Densities of Physical States Gases Least dense Occupy about 16oo greater volume than liquids Liquids Density similar to solids, little less Solids Most dense of states AeroGel—an ultra-low density solid Aerogels have a very good thermal resistance . This photo shows a 2.5 kg Brick being supported by only 2 grams of aerogel Mercury, on the other hand, is a very dense liquid, denser than some solids Figure 3.2: The three states of water. 3.2 Physical and Chemical Properties and Changes AIMS learn to distinguish between physical and chemical properties -learn to distinguish between physical and chemical changes Properties Characteristics of the substance under observation Properties can be either directly observable or the manner something interacts with other substances in the universe Properties of Matter Physical Properties are the characteristics of matter that can be observed without changing its composition Characteristics that are directly observable Chemical Properties are the characteristics that determine how the composition of matter changes as a result of contact with other matter or the influence of energy Characteristics that describe the behavior of matter What is a Physical Property? A physical property is a characteristic of a substance that does not change as you determine that property. Example: In order to determine that a domino is black, all you do is look at it. The domino remains unchanged during the test Example: In order to determine if a rock contains the mineral magnetite, you could place a paperclip nearby and see if it sticks. The rock remains unchanged during this test. Examples of Physical Properties Odor Color Physical state Boiling/melting point Density Magnetic/not Hardness Radioactivity Malleability Ductility Gallium metal has such a low melting point (30°C) that it melts from the heat of a hand. An iron pyrite crystal (gold color) on a white quartz crystal. Source: Chip Clark What is a Chemical Property? A chemical property is a characteristic of a substance which, when determining, will change an example would be …when determining the flammability of a substance, we must burn it, and thereby change it. chemical properties refer to the ability of a substance to form new substances Some Chemical Properties Flammability -is the material flammable? Reactivity -does material react with another chemical, in what way? pH What is the pH of the substance? Classify Each of the following as Physical or Chemical Properties The boiling point of ethyl alcohol is 78°C. Diamond is very hard. Physical property – describes inherent characteristic of alcohol – boiling point Physical property – describes inherent characteristic of diamond – hardness Sugar ferments to form ethyl alcohol. Chemical property – describes behavior of sugar – forming a new substance (ethyl alcohol) Changes in Matter Physical Changes are changes to matter that do not result in a change the fundamental components that make that substance State Changes – boiling, melting, condensing Chemical Changes involve a change in the fundamental components of the substance Produce a new substance Chemical reaction Reactants Products What is a Physical change? Any change that does not change the chemical makeup of a substance Examples include: Changes in physical state Crushing, grinding, tearing What is a Chemical change? Any change that results in materials with a different chemical nature. Examples: Electrolysis Burning (combustion) Silver tarnishing Figure 3.3: Electrolysis, the decomposition of water by an electric current, is a chemical process. Electrolysis Link Signs of a Chemical Change Color Change Formation of a gas (not from a phase change) Energy absorbed or given off Gets cold or hot Gives off light/electric charge/other energy Formation of a precipitate Oxygen combines with the chemicals in wood to produce flames. Is a physical or chemical change taking Source: Jim Pickerell/ Stone/Getty Images place? Classify Each of the following as Physical or Chemical Changes Iron metal is melted. Iron combines with oxygen to form rust. Sugar ferments to form ethyl alcohol. Classify Each of the following as Physical or Chemical Changes Iron is melted. Iron combines with oxygen to form rust.. Physical change – describes a state change, but the material is still iron Chemical change – describes how iron and oxygen react to make a new substance, rust Sugar ferments to form ethyl alcohol. Chemical change – describes how sugar forms a new substance (ethyl alcohol) Classification of Matter Matter Pure Substance Constant Composition Homogeneous Homogeneous = uniform throughout, appears to be one thing Mixture Variable Composition pure substances solutions (homogeneous mixtures) Heterogeneous = non-uniform, contains regions with different properties than other regions 3.3 Elements and Compounds AIM: to understand the definitions of elements and compounds Elements Cannot be separated into simpler substances Fundamental form of matter Examples include iron, oxygen, aluminum, and hydrogen There are 90 naturally occurring elements, about 118 known elements Compounds Have same composition no matter where they are found ALWAYS made up of atoms of 2 or more elements, chemically combined Can be broken into the constituent elements by chemical changes Elements and Compounds Substances which can not be broken down into simpler substances by chemical reactions are called elements Most substances are chemical combinations of elements. These are called compounds. Compounds are made of elements Compounds can be broken down into elements Properties of the compound not related to the properties of the elements that compose it Same chemical composition at all times A Model of an oxygen molecule…. Is this an element or a compound? Element Element Compound Would you put elemental sodium metal and chlorine gas on your popcorn????? Or would you put a compound composed of sodium ion and chloride ion (NaCl) on it? Mixtures vs. Pure Substances Pure Substances vs. Mixtures Pure Substances All samples have a unique set of physical and chemical properties Constant Composition all samples have the same composition Homogeneous (meaning same throughout) Separate into components based on chemical properties Include Elements and Compounds Mixtures Different samples may show different properties Variable composition Homogeneous or Heterogeneous (different throughout) Separate into components based on physical properties All mixtures are made of pure substances Creamtop milk bottles Grain Probe, for sampling corn, soybeans, etc Types of Mixtures Solid mixtures can simply be a mix of various substances, such as pancake mix, or a can of peas and carrots Solid mixtures also include alloys which are physical mixtures of metals. examples 14 K gold, steel, brass Examples Liquid mixture--Ocean water contains water, dissolved salts, oxygen, and other gases Solid mixture--14 K gold contains gold and other metals (only physically combined) Liquid mixture--Blood contains water, dissolved ions, proteins, red blood cells Element, Compound, or Mixture? Types of Mixtures Liquid mixtures fall into the following 3 categories... Solution—particles are dissolved and don’t settle out. Typically transparent, cannot be filtered Colloid-particle size a little bigger, still don’t settle out. Colloids exhibit Tyndall Effect, appear cloudy, murky, or opaque Salt water, Kool-Aid Milk, cloudy water, fog Suspension—particles are fairly large, and will settle out of the mixture, separate upon standing still, can be filtered Air/dust, river water/gravel/mud/sand, Behaviors of Mixtures Suspension - particles are readily sedimented by gravity or by centrifugation. Soil suspension sedimentation by gravity Suspension of blood cells centrifugation at 500 x g No change after centrifugation at 10,000 x g True solutions and colloidal mixtures remain dispersed even following centrifugation. Hemoglobin (true solution) Milk (colloidal mixture) Separation of Mixtures Separate mixtures based on different physical properties of the components Physical change Different Physical Property Technique Boiling Point Distillation State of Matter (solid/liquid/gas) Adherence to a Surface Filtration Chromatography Volatility Evaporation A honey extractor, separates honey from comb Graded sieves Filter paper Used coffee filter Separatory Funnel Figure 3.4: When table salt is stirred into water (left), a homogeneous mixture called a solution forms (right). Figure 3.5: Sand and water do not mix to form a uniform mixture. After the mixture is stirred, the sand settles back to the bottom. Figure 3.6: Distillation of a solution consisting of salt dissolved in water. Identity Each of the following as a Pure Substance, Homogeneous Mixture or Heterogeneous Mixture Gasoline A stream with gravel on the bottom a homogenous mixture a heterogeneous mixture Copper metal A pure substance (all elements are pure substances) Figure 3.10: The organization of matter. Organization of Matter Quia - Mixtures, elements and compounds “Rags to Riches” Game Energy and Energy Changes Capacity to do work chemical, mechanical, thermal, electrical, radiant, sound, nuclear Energy may affect matter e.g. raise its temperature, eventually causing a state change All physical changes and chemical changes involve energy changes Heat Heat: a flow of energy due to a temperature difference 1. Exothermic = A process that results in the evolution of heat. 2. Example: when a match is struck, it is an exothermic process because energy is produced as heat. Endothermic = A process that absorbs energy. Example: melting ice to form liquid water is an endothermic process. Units of Energy One calorie is the amount of energy needed to raise the temperature of one gram of water by 1°C joule kcal = energy needed to raise the temperature of 1000 g of water 1°C 4.184 J = 1 cal In nutrition, calories are capitalized 1 Cal = 1 kcal Example - Converting Calories to Joules Convert 60.1 cal to joules Converting kcal to Joules Convert 56.7 kcal to joules Converting kJ to kcal Convert 45.06 kJ to kcal Figure 3.11: In ice, the water molecules vibrate randomly about their positions in the solid. Their motions are represented by arrows. Figure 3.12: Equal masses of hot water and cold water separated by a thin metal wall in an insulated box. Figure 3.13: The H2O molecules in hot water have much greater random motions than the H2O molecules in cold water. Figure 3.14: The water samples now have the same temperature (50°C) and have the same random motions. Energy and the Temperature of Matter The amount the temperature of an object increases depends on the amount of heat added (Q). If you double the added heat energy the temperature will increase twice as much. The amount the temperature of an object increases depends on its mass If you double the mass it will take twice as much heat energy to raise the temperature the same amount. A burning match releases energy. Source: ElektraVision/ PictureQuest Specific Heat Capacity Specific Heat (c) is the amount of energy required to raise the temperature of one gram of a substance by one Celsius degree J By definition , the specific heat of water is 4.184 g C Amount of Heat = Mass x specific heat x Temperature Change Q = m x c x T Example – Calculate the amount of heat energy (in joules) needed to raise the temperature of 7.40 g of water from 29.0°C to 46.0°C JJ Specific Heat of Water = 4.184 gg-CC Mass = 7.40 g Temperature Change = 46.0°C – 29.0°C = 17.0°C Q = m x c x T J Heat 4.184 7.40g 17.0C 526 J g C Example – A 1.6 g sample of metal that appears to be gold requires 5.8 J to raise the temperature from 23°C to 41°C. Q s m T Is the metal pure gold? Q s m T T 41C - 23C 18C 5.8 J J s 0.20 1.6 g x 18C g C Table 3.2 lists the specific heat of gold as 0.13 Therefore the metal cannot be pure gold. J g C Heating and Cooling Curves Heating Curve As heat added to solid, it first raises the temperature of the solid to the melting point Then added heat goes into melting the solid Temperature stays at the melting point Heat of Fusion As more heat added it raises the temperature of the liquid to the boiling point Then added heat goes into boiling the liquid Temperature stays at the boiling point Heat of Vaporization As more heat added it raises the temperature of the gas Figure 13.2: The heating/cooling curve for water heated or cooled at a constant rate. Heating/Cooling Curve web site http://www.kentchemistry.com/links/Matter/H eatingCurve.htm Energy Requirements for State Changes In order to change a liquid to a gas, must supply the energy required to overcome the all the intermolecular attractions Not break bonds (intramolecular forces) The energy required to boil 1 mole of a liquid is called the Heat of Vaporization Hvaporization = 40.6 kJ/mol for water at 100°C Energy Requirements for State Changes In order to change a solid to a liquid must supply the energy required to overcome the some of the intermolecular attractions The energy required to melt 1 mole of a solid is called the Heat of Fusion Hfusion = 6.02 kJ/mol for ice at 0°C Structures of the States of Matter In solids, the molecules have no translational freedom, they are held in place by strong intermolecular attractive forces In liquids, the molecules have some translational freedom, but not enough to escape their attraction for neighboring molecules may only vibrate they can slide past one another, rotate as well as vibrate In gases, the molecules have “complete” freedom from each other Why do Molecules Attract Each Other? Intermolecular attractions are due to attractive forces between opposite charges + Ion to - ion + End of polar molecule to - end of polar molecule H-bonding especially strong Larger the charge = Stronger attraction Even non-polar molecules have attractions due to opposite charges London Dispersion Forces Figure 13.4: Intramolecular (bonding) forces exist between the atoms in a molecule and hold the molecule together. Intermolecular forces exist between molecules.