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Chapter 4

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  1. Chapter 4 Matter and Energy by Christopher Hamaker Chapter 4

  2. Matter • Matter is any substance that has mass and occupies volume. • Matter exists in one of three physical states: • Solid • Liquid • Gas Chapter 4

  3. Gaseous State • In a gas, the particles of matter are far apart and uniformly distributed throughout the container. • Gases have an indefinite shape and assume the shape of their container. • Gases can be compressed and have an indefinite volume. • Gases have the most energy of the three states of matter. Chapter 4

  4. Liquid State • In a liquid, the particles of matter are loosely packed and are free to move past one another. • Liquids have an indefinite shape and assume the shape of their container. • Liquids cannot be compressed and have a definite volume. • Liquids have less energy than gases, but more energy than solids. Chapter 4

  5. Solid State • In a solid, the particles of matter are tightly packed together. • Solids have a definite, fixed shape. • Solids cannot be compressed and have a definite volume. • Solids have the least energy of the three states of matter. Chapter 4

  6. Physical States of Matter Chapter 4

  7. Changes in Physical States • Most substances can exist as either a solid, a liquid, or a gas. • Water exists as a solid below 0 °C; as a liquid between 0 °C and 100 °C; and as a gas above 100 °C. • A substance can change physical states as the temperature changes. Chapter 4

  8. Solid ↔ Liquid Phase Changes • When a solid changes to a liquid, the phase change is called melting. • A substance melts as the temperature increases. • When a liquid changes to a solid, the phase change is called freezing. • A substance freezes as the temperature decreases. Chapter 4

  9. Liquid ↔ Gas Phase Changes • When a liquid changes to a gas, the phase change is called vaporization. • A substance vaporizes as the temperature increases. • When a gas changes to a liquid, the phase change is called condensation. • A substance condenses as the temperature decreases. Chapter 4

  10. Solid ↔ Gas Phase Changes • When a solid changes directly to a gas, the phase change is called sublimation. • A substance sublimes as the temperature increases. • When a gas changes directly to a solid, the phase change is called deposition. • A substance undergoes deposition as the temperature decreases. Chapter 4

  11. Summary of State Changes Chapter 4

  12. Classifications of Matter • Matter can be divided into two classes: • Mixtures • Pure substances • Mixtures are composed of more than one substance and can be physically separated into its component substances. • Pure substances are composed of only one substance and cannot be physically separated. Chapter 4

  13. Mixtures • There are two types of mixtures: • Homogeneous mixtures • Heterogeneous mixtures • Homogeneous mixtures have uniform properties throughout. • Salt water is a homogeneous mixture. • Heterogeneous mixtures do not have uniform properties throughout. • Sand and water is a heterogeneous mixture. Chapter 4

  14. Pure Substances • There are two types of pure substances: • Compounds • Elements • Compounds can be chemically separated into individual elements. • Water is a compound that can be separated into hydrogen and oxygen. • An element cannot be broken down further by chemical reactions. Chapter 4

  15. Matter Summary Chapter 4

  16. Occurrence of the Elements • There are over 100 elements that occur in nature; 81 of those elements are stable. • Only 10 elements account for 95% of the mass of Earth’s crust: Chapter 4

  17. Elements in the Human Body • Oxygen is the most common element in Earth’s crust and in the human body. • While silicon is the second most abundant element in Earth’s crust, carbon is the second most abundant in the body. Chapter 4

  18. Names of the Elements • Each element has a unique name. • Names have several origins: • Hydrogen is derived from Greek. • Carbon is derived from Latin. • Scandium is named for Scandinavia. • Nobelium is named for Alfred Nobel. • Yttrium is named for the town of Ytterby, Sweden. Chapter 4

  19. Element Symbols • Each element is abbreviated using a chemical symbol. • The symbols are one or two letters long. • Most of the time, the symbol is derived from the name of the element. • C is the symbol for carbon. • Cd is the symbol for cadmium. • When a symbol has two letters, the first is capitalized and the second is lowercase. Chapter 4

  20. Other Element Symbols • For some elements, the chemical symbol is derived from the original Latin name. Chapter 4

  21. Types of Elements • Elements can be divided into three classes: • Metals • Nonmetals • Semimetals or metalloids • Semimetals have properties midway between those of metals and nonmetals. Chapter 4

  22. Metal Properties • Metals are typically solids with high melting points and high densities and have a bright, metallic luster. • Metals are good conductors of heat and electricity. • Metals can be hammered into thin sheets and are said to be malleable. • Metals can be drawn into fine wires and are said to be ductile. Chapter 4

  23. Nonmetal Properties • Nonmetals typically have low melting points and low densities and have a dull appearance. • Nonmetals are poor conductors of heat and electricity. • Nonmetals are not malleable or ductile and crush into a powder when hammered. • Eleven nonmetals occur naturally in the gaseous state. Chapter 4

  24. Summary of Properties Chapter 4

  25. Periodic Table of the Elements • Each element is assigned a number to identify it. It is called the atomic number. • Hydrogen’s atomic number is 1; helium is 2; up to uranium, which is 92. • The elements are arranged by atomic number on the periodic table. Chapter 4

  26. The Periodic Table Chapter 4

  27. Metals, Nonmetals, and Semimetals • Metals are on the left side of the periodic table, nonmetals are on the right side, and the semimetals are in between. Chapter 4

  28. Physical States of the Elements • Shown are the physical states of the elements at 25 °C on the periodic table. Chapter 4

  29. Law of Definite Composition • The law of definite composition states that “Compounds always contain the same elements in a constant proportion by mass.” • Water is always 11.19% hydrogen and 88.81% oxygen by mass, no matter what its source. • Ethanol is always 13.13% hydrogen, 52.14% carbon, and 34.73% oxygen by mass. Chapter 4

  30. Chemical Formulas • A particle composed of two or more nonmetal atoms is a molecule. • A chemical formula is an expression of the number of and types of atoms in a molecule. • The chemical formula of sulfuric acid is H2SO4. Chapter 4

  31. Writing Chemical Formulas • The number of each type of atom in a molecule is indicated with a subscript in a chemical formula. • If there is only one atom of a certain type, no “1” is used. • A molecule of the vitamin niacin has six carbon atoms, six hydrogen atoms, two nitrogen atoms, and one oxygen atom. What is the chemical formula? C6H6N2O Chapter 4

  32. Interpreting Chemical Formulas • Some chemical formulas use parentheses to clarify atomic composition. • Ethylene glycol, a component of some antifreezes, has a chemical formula of C2H4(OH)2. It contains two carbon atoms, four hydrogen atoms, and two OH units, giving a total of six hydrogen atoms and two oxygen atoms. How many total atoms are in ethylene glycol? • Ethylene glycol has a total of ten atoms. Chapter 4

  33. Physical and Chemical Properties • A physical property is a characteristic of a pure substance that we can observe without changing its composition. • Physical properties include appearance, melting and boiling points, density, conductivity, and physical state. • A chemical property describes the chemical reactions of a pure substance. Chapter 4

  34. Chemical Properties Sodium metal (Na) reacts with chlorine gas (Cl2) to produce sodium chloride (NaCl). Chapter 4

  35. Physical and Chemical Change • A physical change is a change where the chemical composition of the substance is not changed. • These include changes in physical state or shape of a pure substance. • A chemical change is a chemical reaction. • The composition of the substances changes during a chemical change. Chapter 4

  36. Evidence for Chemical Changes • Gas release (bubbles) • Light or release of heat energy • Formation of a precipitate • A permanent color change Chapter 4

  37. Conservation of Mass • Antoine Lavoisier found that the mass of substances before a chemical change was always equal to the mass of substances after a chemical change. • This is the law of conservation of mass. • Matter is neither created nor destroyed in physical or chemical processes. Chapter 4

  38. Conservation of Mass Example • If 1.0 gram of hydrogen combines with 8.0 grams of oxygen, 9.0 grams of water is produced. • Consequently, 3.0 grams of hydrogen combine with 24.0 grams of oxygen to produce 27.0 grams of water. • If 50.0 grams of water decompose to produce 45.0 grams of oxygen, how many grams of hydrogen are produced? 50.0 g water – 45.0 g oxygen = 5.0 g hydrogen Chapter 4

  39. Potential and Kinetic Energy • Potential energy, PE, is stored energy; it results from position or composition. • Kinetic energy, KE, is the energy matter has as a result of motion. • Energy can be converted between the two types. • A boulder at the top of the hill has potential energy; if you push it down the hill, the potential energy is converted to kinetic energy. Chapter 4

  40. Energy Chapter 4

  41. KE, Temperature, and Physical State • All substances have kinetic energy regardless of their physical state. • Solids have the lowest kinetic energy, and gases have the greatest kinetic energy. • As you increase the temperature of a substance, its kinetic energy increases. Chapter 4

  42. Law of Conservation of Energy • Just like matter, energy cannot be created or destroyed, but it can be converted from one form to another. • This is the law of conservation of energy. • There are six forms of energy: • Heat • Light • Electrical • Mechanical • Chemical • Nuclear Chapter 4

  43. Energy and Chemical Changes • In a chemical change, energy is transformed from one form to another. For example: Chapter 4

  44. Law of Conservation of Mass and Energy • Mass and energy are related by Einstein’s theory of relativity, E = mc2. • Mass and energy can be interchanged. • The law of conservation of mass and energy states that the total mass and energy of the universe is constant. Chapter 4

  45. Chemistry Connection: Al Recycling • Although aluminum is very abundant in Earth’s crust, it is difficult to purify it from its ore. • The energy from 8 tons of coal is required to produce 1 ton of aluminum metal from its ore. • However, it only takes the energy from 0.4 tons of coal to produce 1 ton of aluminum from recycled scrap. Chapter 4

  46. Chapter Summary • Matter exists in three physical states: • Solid • Liquid • Gas • Substances can be converted between the three states. • Substances can be mixtures or pure substances. Chapter 4

  47. Chapter Summary, Continued • Pure substances can be either compound or elements. • The elements are arranged in the periodic table. • Each element has a name and a one- or two-letter symbol. • Elements are classified as either metals, nonmetals, or semimetals. Chapter 4

  48. Chapter Summary, Continued • A physical change is a change in physical state or shape. • A chemical change is a change in the chemical composition of a substance. • Both mass and energy are conserved in chemical and physical changes. Chapter 4