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Chapter 3 Matter and Energy

Chapter 3 Matter and Energy. Matter. Matter is anything that occupies space and has mass. Even though it appears to be smooth and continuous, matter is actually composed of a lot of tiny little pieces we call atoms and molecules. Atoms and Molecules.

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Chapter 3 Matter and Energy

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  1. Chapter 3 Matter and Energy

  2. Matter • Matter is anything that occupies space and has mass. • Even though it appears to be smooth and continuous, matter is actually composed of a lot of tiny little pieces we call atoms and molecules. Tro's "Introductory Chemistry", Chapter 3

  3. Atoms and Molecules • Atoms are the tiny particles that make up all matter. • In most substances, the atoms are joined together in units called molecules. Tro's "Introductory Chemistry", Chapter 3

  4. Classification of Matter Matter can be classified in two ways: 1- according to its physical state 2- according to its composition Tro's "Introductory Chemistry", Chapter 3 4

  5. Classification of Matter According to its Physical State (STATES OF MATTER) Matter can be classified as solid, liquid, or gas MATTER SOLID e.g. stone, charcoal, diamond LIQUID e.g. water, wine, vinegar GAS e.g. oxygen, carbon dioxide Tro's "Introductory Chemistry", Chapter 3

  6. Solids • The particles in a solid are packed close together and are fixed in position. • Due to this close parking solids are incompressible. • The inability of the particles to move around results in solids retaining their shape and volume when placed in a new container and prevents the particles from flowing. • Solids may be further classified as: • Crystalline Solids • Amorphous Solids Tro's "Introductory Chemistry", Chapter 3

  7. Crystalline vs Amorphous • Some solids have their particles arranged in an orderly geometric pattern—we call these crystalline solids. • Salt and diamonds. • Other solids have particles that do not show a regular geometric pattern over a long range—we call these amorphous solids. • Plastic and glass. Tro's "Introductory Chemistry", Chapter 3

  8. Liquids • The particles in a liquid are closely packed, but they have some ability to move around. • The close packing results in liquids being incompressible. • The ability of the particles to move allows liquids to take the shape of their container and to flow. However, they don’t have enough freedom to escape and expand to fill the container. Tro's "Introductory Chemistry", Chapter 3

  9. Gases • In the gas state, the particles have complete freedom from each other. • The particles are constantly flying around, bumping into each other and the container. • In the gas state, there is a lot of empty space between the particles. • On average. Tro's "Introductory Chemistry", Chapter 3

  10. Gases, Continued • Because there is a lot of empty space, the particles can be squeezed closer together. Therefore, gases are compressible. • Because the particles are not held in close contact and are moving freely, gases expand to fill and take the shape of their container, and will flow. Tro's "Introductory Chemistry", Chapter 3

  11. Summary: Properties of Solids, Liquids and Gases Tro's "Introductory Chemistry", Chapter 3

  12. Matter Pure Substance Mixture Constant Composition Variable Composition Classification of Matter by Composition Tro's "Introductory Chemistry", Chapter 3

  13. Classification of Matter as a pure substance A pure substance is made of a single type of particle (i.e., atom or molecule). The composition of a pure substance does not change from one sample to another and because of this, all samples have the same characteristics (or properties) Tro's "Introductory Chemistry", Chapter 3

  14. Classification of Matter as a Pure Substance • Pure substances can further be sub-divided into two groups: • Elements • Compounds Elements: Pure substances that cannot be broken down into simpler substances e.g., copper, helium, sodium Compounds: Pure substances that are made of two or more elements in definite proportions e.g., sodium chloride NaCl, Carbon dioxide CO2 Tro's "Introductory Chemistry", Chapter 3

  15. Classification of Matter as a Mixture A mixture is a combination of two or more substances in which each substance retain their distinct characteristics (or properties). e.g., a mixture of rice and sand • Mixtures can also be further sub-divided into two groups: • Homogeneous mixture • Heterogeneous mixture Homogeneous mixture: Has uniform composition through out the sample e.g.,solutions such as tea with sugar, salt solutions Heterogeneous mixture: Does not have a uniform composition through out the sample. e.g., sand and water Note: HOMO means the same while HETERO means different Tro's "Introductory Chemistry", Chapter 3

  16. Example—Classify the Following as Homogeneous or Heterogeneous Mixtures • A cup of coffee • A mixture of table sugar and black pepper • A mixture of sugar dissolved in water • Sand and water -homogeneous -heterogeneous -homogeneous -heterogeneous Tro's "Introductory Chemistry", Chapter 3

  17. Classifying Matter

  18. How Do We Distinguish Matter? acid water • Looking at both flasks, it is had to tell the difference between the two substances • How can we tell if one flask contain water and the other contains an acid? • We can only tell by studying their properties Tro's "Introductory Chemistry", Chapter 3

  19. Properties of Matter • Each sample of matter is distinguished by its characteristics. • The characteristics of a substance are called its properties. Tro's "Introductory Chemistry", Chapter 3

  20. Types of Properties of Matter • Physical Properties Properties of matter that can be observed without changing its composition. • e.g., coke is dark brown • Chemical Properties Properties of matter that can be observed only when matter changes its composition. • e.g., gasoline is a very flammable liquid Tro's "Introductory Chemistry", Chapter 3

  21. Some Physical Properties Tro's "Introductory Chemistry", Chapter 3

  22. Example: Some Physical Properties of Iron • Iron melts at 1538 °C • Iron boils at 4428 °C. • Iron’s density is 7.87 g/cm3. • Iron conducts electricity, but not as well as most other common metals. Tro's "Introductory Chemistry", Chapter 3

  23. Some Chemical Properties Tro's "Introductory Chemistry", Chapter 3

  24. Example: Some Chemical Properties of Iron • Iron is easily oxidized in moist air to form rust. • When iron is added to hydrochloric acid, it produces a solution of ferric chloride and hydrogen gas. • Iron is more reactive than silver, but less reactive than magnesium. Tro's "Introductory Chemistry", Chapter 3

  25. Example—Decide Whether Each of the Observations About Table Salt Is a Physical or Chemical Property physical • Salt is a white, granular solid. • Salt melts at 801 °C. • A liquid burns with a blue flame. • 36 g of salt will dissolve in 100 g of water. • Salt solutions conduct electricity. • When a clear, colorless solution of silver nitrate is added to a salt solution, a white solid forms. • When electricity is passed through molten salt, a gray metal forms at one terminal and a yellow-green gas at the other. physical chemical physical physical chemical chemical Tro's "Introductory Chemistry", Chapter 3

  26. Changes in Matter • Changes that alter the state or appearance of matter without altering its composition are called physical changes. • Changes that alter the composition of matter are called chemical changes. Tro's "Introductory Chemistry", Chapter 3

  27. PhysicalChanges in Matter • Physical Changes—Changes that do not affect composition of matter. • Heating water. • Raises its temperature, but it is still water. • Evaporating butane from a lighter. • Dissolving sugar in water. • Even though the sugar seems to disappear, it can easily be separated back into sugar and water by evaporation. Tro's "Introductory Chemistry", Chapter 3

  28. Changes in Matter, Continued • Chemical Changes— involve a change in composition. • A chemical reaction. • Silver combines with sulfur in the air to make tarnish. • Rusting is iron combining with oxygen to make iron(III) oxide. • Burning results in butane from a lighter to be changed into carbon dioxide and water. Tro's "Introductory Chemistry", Chapter 3

  29. Is it a Physical or Chemical Change? • A physical change results in a different form of the same substance. • The kinds of molecules don’t change. i.e., composition stays the same . • A chemical change results in one or more completely new substances. • The new substances have different molecules than the original substances. i.e., composition changes. • Appearance may or may not change. • You will observe different physical properties because the new substances have their own physical properties. Tro's "Introductory Chemistry", Chapter 3

  30. Phase Changes ArePhysical Changes • Vaporizing = liquid to gas. • Melting = solid to liquid. • Subliming = solid to gas. • Freezing = liquid to solid. • Condensing = gas to liquid. • Deposition = gas to solid. • Changes in the state of matter require heating or cooling the substance. Tro's "Introductory Chemistry", Chapter 3

  31. Example—Classify Each Change as Physical or Chemical, Continued • Evaporation of rubbing alcohol. • Sugar turning black when heated. • An egg splitting open and spilling out. Physical change Chemical change Physical change Tro's "Introductory Chemistry", Chapter 3

  32. Practice—Classify Each Change as Physical or Chemical • Sugar fermenting. • Bubbles escaping from soda. • Bubbles that form when hydrogen peroxide is mixed with blood. Tro's "Introductory Chemistry", Chapter 3

  33. Different Physical Property Different Physical Property Technique Technique Boiling point Boiling point Distillation Distillation State of matter (solid/liquid/gas) State of matter (solid/liquid/gas) Filtration Filtration Adherence to a surface Adherence to a surface Chromatography Chromatography Volatility Volatility Evaporation Evaporation Density Density Decanting Decanting Separation of Mixtures • Separating mixtures based on different physical properties of their components. Tro's "Introductory Chemistry", Chapter 3

  34. Distillation Tro's "Introductory Chemistry", Chapter 3

  35. Filtration Tro's "Introductory Chemistry", Chapter 3

  36. Law of Conservation of Mass • The law of conservation of mass states: “Matter is neither created nor destroyed in a chemical reaction.” • The total amount of matter present before a chemical reaction is always the same as the total amount after. • Example: 58 grams of butane burns in 208 grams of oxygen to form 176 grams of carbon dioxide and 90 grams of water. • butane + oxygen  carbon dioxide + water • 58 grams + 208 grams  176 grams + 90 grams • 266 grams = 266 grams Tro's "Introductory Chemistry", Chapter 3

  37. Practice—A Student Places Table Sugar and Sulfuric Acid into a Beaker and Gets a Total Mass of 144.0 g. Shortly, a Reaction Starts that Produces a “Snake” of Carbon Extending from the Beaker and Steam Is Seen Escaping. If the Carbon Snake and Beaker at the End Have a Total Mass of 129.6 g, How Much Steam Was Produced? Tro's "Introductory Chemistry", Chapter 3

  38. Energy • Energy is anything that has the capacity to do work. • Unlike matter, energy does not have mass and does not occupy any space. • Although chemistry is the study of matter, matter is effected by energy. • It can cause physical and/or chemical changes in matter. Tro's "Introductory Chemistry", Chapter 3

  39. Law of Conservation of Energy • “Energy can neither be created nor destroyed.” • The total amount of energy in the universe is constant. There is no process that can increase or decrease that amount. • However, we can transfer energy from one place in the universe to another, and we can also change energy from one form to another. Tro's "Introductory Chemistry", Chapter 3

  40. Kinds of EnergyKinetic and Potential • Potential energy is energy that is stored. • Water flows because gravity pulls it downstream. • However, the dam won’t allow it to move, so it has to store that energy. • Kinetic energy is energy of motion, or energy that is being transferred from one object to another. • When the water flows over the dam, some of its potential energy is converted to kinetic energy of motion. Tro's "Introductory Chemistry", Chapter 3

  41. Some Forms of Energy • Electrical Energy • Kinetic energy associated with the flow of electrical charge. • Heat or Thermal Energy • Kinetic energy associated with molecular motion. • Light or Radiant Energy • Kinetic energy associated with energy transitions in an atom. • Nuclear Energy • Potential energy stored in the nucleus of atoms. • Chemical Energy • Potential energy in compounds. Tro's "Introductory Chemistry", Chapter 3

  42. Converting Forms of Energy • When water flows over the dam, some of its potential energy is converted to kinetic energy. • Some of the energy is stored in the water because it is at a higher elevation than the surroundings. • The movement of the water is kinetic energy. • Along the way, some of that energy can be used to push a turbine to generate electricity. • Electricity is one form of kinetic energy. • The electricity can then be used in your home. For example, you can use it to heat cake batter you mixed, causing it to change chemically and storing some of the energy in the new molecules that are made. Tro's "Introductory Chemistry", Chapter 3

  43. How do We Measure Energy?Units of Energy • The SI unit for energy is the joule (J) • Other units such as calorie, Calorie, KWh are widely used • calorie (cal) is the amount of energy needed to raise one gram of water by 1 °C. • 1 kcal = energy needed to raise 1000 g of water 1 °C. • 1 food calories (Cal) = 1 kcals. Tro's "Introductory Chemistry", Chapter 3

  44. Some Common Uses of Energy Use Tro's "Introductory Chemistry", Chapter 3

  45. Example 3.5—Convert 225 Cal to Joules • Write down the Given quantity and its unit. Given: 225 Cal 3 sig figs • Write down the quantity you want to Find and unit. Find: ? J • Write down the appropriate Conversion Factors. Conversion Factors: 1 Cal = 1000 cal 1 cal = 4.184 J • Write a Solution Map. Solution Map: Cal cal J • Follow the solution map to Solve the problem. Solution: • Significant figures and round. Round: 225 Cal = 9.41 x 105 J 3 significant figures

  46. Practice 1: The complete combustion of a wooden match produces 512 cal of heat. How many kilojoules are produced? Answer: 2.14 kJ Practice 2: An energy bill indicates that the customer used 955 KWh. How many calories did the customer use? Answer: 8.22 x exp(8) cal.

  47. Practice 1: The complete combustion of a wooden match produces 512 cal of heat. How many kilojoules are produced? Answer: 2.14 kJ Tro's "Introductory Chemistry", Chapter 3

  48. Practice 2: An energy bill indicates that the customer used 955 KWh. How many calories did the customer use? Answer: 8.22 x exp(8) cal.

  49. Energy Changes • Processes that involve energy changes can be: • Exothermic • Endothermic Tro's "Introductory Chemistry", Chapter 3

  50. Exothermic Processes • When a change results in the release of energy it is called an exothermic process. • An exothermic chemical reaction occurs when the reactants have more chemical potential energy than the products. • The excess energy is released into the surrounding materials, adding energy to them. • Often the surrounding materials get hotter from the energy released by the reaction. Tro's "Introductory Chemistry", Chapter 3

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