Unit 2 Notes

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Unit 2 Notes

  1. 1. Science 10F Unit 2 – Atoms & Elements
  2. 2. What is chemistry? Chemistry is the study of MATTER and the changes that take place with matter.
  3. 3. WHMIS & MSDS Science 10F Unit 2 – Atoms & Elements
  4. 4. Historical Ideas About the Nature of Matter <ul><li>Ancient Greek Philosophers: </li></ul><ul><li>The ancient Greek philosophers wondered why matter behaves as it does and manipulated ideas in their minds but did almost no experimentation. </li></ul><ul><li>Empedocles 450 BCE </li></ul><ul><ul><li>Empedocles proposed that matter was composed of four elements: Earth, Water, Air, Fire. </li></ul></ul><ul><li>Democritus 400 BCE </li></ul><ul><ul><li>Democritus suggested matter was made of tiny particles that could not be broken down further. He called these particles “atomos,” which means indivisible. </li></ul></ul>Science 10F Unit 2 – Atoms & Elements
  5. 5. Historical Ideas About the Nature of Matter <ul><li>Aristotle 350 BCE </li></ul><ul><ul><li>After the death of Democritus, Aristotle and Socrates rejected the atomic model and adopted Empedocles’ “four element” model. This model influenced and dominated scientific thinking for almost 2000 years. </li></ul></ul>Science 10F Unit 2 – Atoms & Elements
  6. 6. Historical Ideas About the Nature of Matter <ul><li>Alchemists 500–1600 AD </li></ul><ul><li>The alchemists were the first people to perform hands-on experimentation. They were part philosopher, mystic, magician, and chemist. </li></ul><ul><ul><li>They had three main beliefs: </li></ul></ul><ul><ul><li>i. They believed that some elements could be changed into others. They attempted to change base metals(lead, tin) into valuable ones like gold, but in the process discovered new elements as well as many facts about existing materials. </li></ul></ul><ul><ul><li>ii. They believed they could find a substance that would give them eternal life. </li></ul></ul><ul><ul><li>iii. They believed they could produce a universal solvent that would dissolve all substances. </li></ul></ul>Science 10F Unit 2 – Atoms & Elements
  7. 7. Historical Ideas About the Nature of Matter <ul><li>Modern Chemists: 1600–Present </li></ul><ul><li>These chemists used the scientific method to investigate the physical world. This began in the 17th and 18th centuries where the focus was on determining the properties of pure substances and attempting to explain their composition. </li></ul>Science 10F Unit 2 – Atoms & Elements
  8. 8. Historical Ideas About the Nature of Matter <ul><li>Robert Boyle (1650) </li></ul><ul><ul><li>Boyle believed that the Greek philosophers’ “four element” theory could be improved upon. He published “The Skeptical Chemist” in which he defined an element as “certain simple unmingled bodies….” Boyle also helped lay the foundation for the concepts of elements and compounds. He recognized that elements could be combined to form compounds. Boyle also believed that air was not an element but a mixture. </li></ul></ul><ul><li>Joseph Priestly (late 1700s) </li></ul><ul><ul><li>Priestly was the first person to isolate oxygen scientifically, but did not know that oxygen was an element. </li></ul></ul>Science 10F Unit 2 – Atoms & Elements
  9. 9. Historical Ideas About the Nature of Matter <ul><li>Antoine de Lavoisier (late 1700s) </li></ul><ul><ul><li>Lavoisier defined the term “element” as a pure substance that cannot be chemically broken down into simpler substances. </li></ul></ul><ul><ul><li>He discovered and identified 23 elements. He based his investigations on careful measurement and observations. </li></ul></ul><ul><ul><li>He recognized mixtures exist and identified air as a mixture of oxygen and some other gas. </li></ul></ul><ul><li>Henry Cavendish (late 1700s) </li></ul><ul><ul><li>Cavendish experimented by mixing metal with acid, which produced a flammable gas (hydrogen). He discovered that his gas would burn in oxygen and produce water. Until that time, water was thought to be an element. </li></ul></ul>Science 10F Unit 2 – Atoms & Elements
  10. 10. Models of the Atom <ul><li>Once scientists realized that matter is made up of small particles they began to develop a model for the structure of matter. </li></ul>Science 10F Unit 2 – Atoms & Elements
  11. 11. Models of the Atom Science 10F Unit 2 – Atoms & Elements
  12. 12. Dalton’s Model of the Atom <ul><li>In the atomic theory, Dalton stated that: </li></ul><ul><ul><li>all matter is made of atoms (particles too small to see) </li></ul></ul><ul><ul><li>each element has its own kind of atom (atoms of the same element have the same mass; atoms of different elements have different masses) </li></ul></ul><ul><ul><li>compounds are created when </li></ul></ul><ul><ul><li>atoms of different elements </li></ul></ul><ul><ul><li>combine </li></ul></ul><ul><ul><li>atoms cannot be created or </li></ul></ul><ul><ul><li>destroyed </li></ul></ul>Science 10F Unit 2 – Atoms & Elements
  13. 13. Thomson’s Model of the Atom <ul><li>Thomson contributed to the atomic model by hypothesizing that: </li></ul><ul><ul><li>Atoms contain particles called electrons </li></ul></ul><ul><ul><li>Electrons have a small mass and a negative charge </li></ul></ul><ul><ul><li>The rest of the atom is a </li></ul></ul><ul><ul><li>sphere of positive charge </li></ul></ul><ul><ul><li>Electrons are embedded </li></ul></ul><ul><ul><li>in the sphere, making the </li></ul></ul><ul><ul><li>atoms neutral </li></ul></ul>Science 10F Unit 2 – Atoms & Elements
  14. 14. Rutherford’s Model of the Atom <ul><li>Rutherford contributed to the atomic model by hypothesizing: </li></ul><ul><ul><li>The nucleus is a very small, dense, positively charged core of the atom </li></ul></ul><ul><ul><li>All of the atoms positively </li></ul></ul><ul><ul><li>charged particles, called </li></ul></ul><ul><ul><li>protons, are located in </li></ul></ul><ul><ul><li>the nucleus of the atom. </li></ul></ul>Science 10F Unit 2 – Atoms & Elements
  15. 15. Bohr’s Model of the Atom <ul><li>This model depicts the atom as a small, positively charged nucleus surrounded by waves of electrons in orbit - similar in structure to the solar system. </li></ul><ul><li>Niels Bohr's model of the </li></ul><ul><li>atom proposed that electrons </li></ul><ul><li>occupy special positions </li></ul><ul><li>around the nucleus. </li></ul><ul><li>These special positions are </li></ul><ul><li>called orbits or shells . </li></ul>Science 10F Unit 2 – Atoms & Elements
  16. 16. Science 10F Unit 2 – Atoms & Elements
  17. 17. Quantum Model of the Atom <ul><li>The Quantum model proposed the following: </li></ul><ul><ul><li>According to the theory of wave mechanics, electrons do not move about the atom's nucleus in a definite path like planets around the Sun. </li></ul></ul><ul><ul><li>It is impossible to determine the exact location of an electron. </li></ul></ul><ul><ul><li>The probable location of an electron is based on its energy. </li></ul></ul><ul><ul><li>Energy levels are divided into four sublevels, and each sublevel is made up of several pairs of electrons called orbitals. </li></ul></ul><ul><ul><li>The quantum model of the atom shows how electrons move randomly in electron clouds called orbitals. </li></ul></ul>Science 10F Unit 2 – Atoms & Elements
  18. 18. Atomic Nucleus <ul><li>Henry Moseley worked on the structure of the nucleus of the atom. Moseley discovered that the nucleus is filled with positive charges that are closely related to the atomic weight of the atom and its chemical activity. Moseley discovered an orderly increase in the positive charge of an atom as the atomic weight increased. </li></ul><ul><li>Ernest Rutherford suggested the name proton for the unit positive charge in the nucleus. </li></ul>Science 10F Unit 2 – Atoms & Elements
  19. 19. Atomic Nucleus <ul><li>Chadwick worked with Rutherford on his experiments. As they discovered the proton, they came to understand that protons could not account for the total mass of the nucleus. There had to be another particle, also located in the nucleus, which had no charge. It did not have a charge because the negative charge produced by the electrons was already balanced by the positive charges provided by the protons. The particle in the nucleus that Chadwick discovered is called a neutron (Rutherford suggested the name). The neutron has a mass approximately equal to the mass of a proton but has no electric charge. </li></ul><ul><li>Protons and neutrons are both located in the nucleus of the atom. </li></ul>Science 10F Unit 2 – Atoms & Elements
  20. 20. Atomic Structure <ul><li>Every atom is made of three smaller or subatomic particles. </li></ul><ul><ul><li>Electrons Electrons travel outside the nucleus of the atom. Electrons have a charge of -1 Electrons have an extremely small mass, for our purposes it is zero </li></ul></ul><ul><ul><li>Protons Protons are located in the nucleus of the atom Protons have a mass of one atomic mass unit(u) Protons have a charge of +1 </li></ul></ul><ul><ul><li>Neutrons Neutrons are located in the nucleus of the atom Neutrons have a mass of approximately one atomic mass unit(u) Neutrons have no charge </li></ul></ul>Science 10F Unit 2 – Atoms & Elements
  21. 21. Atomic Structure Science 10F Unit 2 – Atoms & Elements
  22. 22. Science 10F Unit 2 – Atoms & Elements
  23. 23. Atomic Structure Science 10F Unit 2 – Atoms & Elements   Charge Location Mass Discovered by: Protons         Electrons         Neutrons        
  24. 24. Atomic Number <ul><li>Henry Moseley originally developed the concept of atomic number. The atomic number is determined by the number of protons in the nucleus. The atomic number is special because it can be used to identify any known element. It is easy to identify copper because it has an atomic number of 29. Carbon has an atomic number of six, oxygen has an atomic number of eight, and so on. </li></ul>Science 10F Unit 2 – Atoms & Elements
  25. 25. Atomic Number Science 10F Unit 2 – Atoms & Elements   Iron ( ) Krypton ( ) Uranium ( ) Sodium ( ) Atomic Number         Number of Protons        
  26. 26. Mass Number <ul><li>All atoms have a mass number. The mass number is equal to the number of protons plus the number of neutrons (e.g., carbon has six protons and six neutrons). The mass number for carbon would be </li></ul><ul><li>6 (protons) + 6 (neutrons) = 12. </li></ul><ul><li>Since a proton and a neutron each have close to the same mass - one amu, the mass number of carbon would be 12 amu. </li></ul><ul><li>MASS NUMBER = NUMBER OF PROTONS (ATOMIC NUMBER) + NUMBER OF NEUTRONS </li></ul>Science 10F Unit 2 – Atoms & Elements
  27. 27. Mass Number Science 10F Unit 2 – Atoms & Elements   Lithium ( ) Chlorine ( ) Copper ( ) Silver ( ) Number of Protons         Number of Neutrons         Mass Number        
  28. 28. Atomic Mass & Isotopes <ul><li>Certain elements can exist in varying forms or isotopes. All atoms of the same element contain the same number of protons and electrons but can vary in the number of neutrons. As a result the mass number of these elements will vary. </li></ul><ul><li>Ex. C 12 or C 14 </li></ul><ul><li>An elements atomic mass is based on the amount of the different isotopes for an element. </li></ul>Science 10F Unit 2 – Atoms & Elements
  29. 29. Determining the Number of Subatomic Particles <ul><li>Number of protons </li></ul><ul><ul><li>The number of protons is equal to the atomic number . </li></ul></ul><ul><li>Number of electrons </li></ul><ul><ul><li>All atoms are electrically neutral; that is, they have equal numbers of protons and electrons. In any atom the number of electrons is equal to the atomic number . </li></ul></ul><ul><li>Number of neutrons </li></ul><ul><ul><li>The mass number is always equal to the number of protons plus the number of neutrons. The number of neutrons would then be equal to the mass number minus the atomic number . </li></ul></ul>Science 10F Unit 2 – Atoms & Elements
  30. 30. Bohr Diagrams Science 10F Unit 2 – Atoms & Elements
  31. 31. Meet the Elements Science 10F Unit 2 – Atoms & Elements
  32. 32. Meet the Elements <ul><li>The number of elements known to man numbers well over 100. In order to remember them, Jacob Berzelius, began giving the elements symbols to represent them. This system involves a worldwide language, used by all nations. </li></ul><ul><li>How do the elements get their symbols? </li></ul>Science 10F Unit 2 – Atoms & Elements
  33. 33. Meet the Elements <ul><li>1. Some elements are represented by one letter. This letter will be the first letter in the name and will capitalized. (H, C, N, O) </li></ul><ul><li>2. Other elements will have symbols using the first two letters of the name (or 1 st and 3rd). The first will be capitalized, the second is lower case. (Ex. He, Ni, Ca, Al) </li></ul><ul><li>3. Many symbols had a Latin origin and as a result their symbols relate to the Latin name. (Ex. Iron – Fe – comes from the Latin name ferrum) </li></ul>Science 10F Unit 2 – Atoms & Elements
  34. 34. Science 10F Unit 2 – Atoms & Elements It's ary! ELEMENT
  35. 35. Science 10F Unit 2 – Atoms & Elements
  36. 36. Science 10F Unit 2 – Atoms & Elements The PERIODIC TABLE of ELEMENTS
  37. 37. Science 10F Unit 2 – Atoms & Elements
  38. 38. Mendeleev’s Early Periodic Table of Elements <ul><li>By the middle of the nineteenth century scientists, had discovered approximately 63 elements. Scientists arranged elements alphabetically because there was no system for classification. </li></ul><ul><li>Dmitri Mendeleev, a Russian </li></ul><ul><li>scientist and professor, placed </li></ul><ul><li>characteristic properties of elements </li></ul><ul><li>on pieces of paper and arranged </li></ul><ul><li>them in many different ways. </li></ul><ul><li>He discovered a certain pattern </li></ul><ul><li>or repetition of properties. </li></ul>Science 10F Unit 2 – Atoms & Elements
  39. 39. Mendeleev’s Early Periodic Table of Elements Science 10F Unit 2 – Atoms & Elements
  40. 40. Mendeleev’s Early Periodic Table of Elements <ul><li>This repetition of properties or periodicity was an important outcome of Mendeleev's work. Mendeleev used the periodicity of properties to create a periodic table . This table summarized the structure and properties of the elements. The periodic law states: If elements are arranged according to their atomic mass, a pattern can be seen in which similar characteristic properties occur regularly . </li></ul>Science 10F Unit 2 – Atoms & Elements
  41. 41. Mendeleev’s Early Periodic Table of Elements <ul><li>Mendeleev's First Periodic Table </li></ul>Science 10F Unit 2 – Atoms & Elements
  42. 42. Mendeleev’s Early Periodic Table of Elements <ul><li>Mendeleev transformed earlier understanding about the classification of elements into a grand plan called the periodic table. </li></ul><ul><li>Mendeleev discovered (with a few exceptions) that arranging elements in order of increasing atomic mass across rows and similar characteristic properties down columns would result in elements obeying the periodic law (i.e., they repeated their characteristic properties regularly). </li></ul><ul><li>Mendeleev believed that missing elements had yet to be discovered. Mendeleev left these spots open, predicted their characteristic properties accurately, and expected that these elements were yet to be discovered. </li></ul><ul><li>The exceptions to the increasing atomic mass rule were iodine and tellurium. Mendeleev handled the problem by placing the element in the periodic table according to characteristic properties and ignored the atomic mass. </li></ul><ul><li>Moseley solved Mendeleev's problem by arranging elements in order of increasing atomic number. </li></ul>Science 10F Unit 2 – Atoms & Elements
  43. 43. Chemical Solitaire Science 10F Unit 2 – Atoms & Elements Br Kt Cr Dd Ti     Pt Sn   Wb   F S Bh R W   Ar La Tp L   Tv T O
  44. 44. The Modern Periodic Table <ul><li>As you probably saw, the periodic table is organized like a big grid. The ELEMENTS are placed in specific places because of the way they look and act. </li></ul><ul><li>The periodic table has </li></ul><ul><li>rows (left to right) and </li></ul><ul><li>columns (up and down). </li></ul>Science 10F Unit 2 – Atoms & Elements
  45. 45. The Modern Periodic Table Science 10F Unit 2 – Atoms & Elements
  46. 46. The Modern Periodic Table <ul><li>PERIODS </li></ul><ul><li>When you look at a periodic table, each of the rows are considered to be different PERIODS. They are numbered from 1-7. </li></ul><ul><li>In the periodic table, elements have something in common if they are in the same row. All of the elements in a PERIOD have the same number of SHELLS. </li></ul><ul><li>So, every element in the top row (the first period) has one shell for its electrons. All of the elements in the second row (the second period) have two shells for their electrons. It goes down the periodic table like that. </li></ul>Science 10F Unit 2 – Atoms & Elements
  47. 47. The Modern Periodic Table <ul><li>PERIODS </li></ul>Science 10F Unit 2 – Atoms & Elements
  48. 48. The Modern Periodic Table <ul><li>Groups </li></ul><ul><li>The periodic table has a special name for its columns too. When a column goes from top to bottom, its called a GROUP. </li></ul><ul><li>The groups are numbered 1-18. The elements in a group have the same number of electrons in their outer shell. </li></ul><ul><li>Every element in the first column (group one) has one electron is its outer shell. Every element on the second column (group two) has two electrons in the outer shell. This trend continues for groups 13-18. Groups 3-12 are somewhat different. </li></ul>Science 10F Unit 2 – Atoms & Elements
  49. 49. The Modern Periodic Table <ul><li>GROUPS </li></ul>Science 10F Unit 2 – Atoms & Elements
  50. 50. The Modern Periodic Table <ul><li>Assignment </li></ul><ul><li>The following should be placed on the blank periodic table that you have been given: </li></ul><ul><li>Color and Identify the following Families </li></ul><ul><li>1. chalcogens </li></ul><ul><li>2. alkaline earth metals </li></ul><ul><li>3. noble gases </li></ul><ul><li>4. halogens </li></ul><ul><li>5. alkali metals </li></ul><ul><li>6. transition metals </li></ul><ul><li>7. lanthanide series </li></ul><ul><li>8. actinide series </li></ul><ul><li>Draw a line that separates the metals from the non-metals. </li></ul><ul><li>Label the periods and groups. </li></ul>Science 10F Unit 2 – Atoms & Elements
  51. 51. Science 10F Unit 2 – Atoms & Elements
  52. 52. The Modern Periodic Table <ul><li>Metals </li></ul><ul><li>Metals constitute more than 75% of the elements. They are located throughout the periodic table, and are concentrated on the left side and centre. </li></ul><ul><li>Physical propertie s: shiny, generally silver-grey in colour (except gold and copper), malleable, ductile, solid at room temperature (except mercury), conduct heat, and conduct electricity. </li></ul>Science 10F Unit 2 – Atoms & Elements
  53. 53. The Modern Periodic Table <ul><li>Non-Metals </li></ul><ul><li>Nonmetals constitute about 15% of the elements. They are located on the far-right side of the periodic table. </li></ul><ul><li>Physical propertie s: no lustre, brittle (not malleable or ductile), nonconductors or insulators of heat, nonconductors or insulators of electricity (except graphite), and either solid or gas at room temperature (except bromine). </li></ul>Science 10F Unit 2 – Atoms & Elements
  54. 54. The Modern Periodic Table <ul><li>Metalloids </li></ul><ul><li>Metalloids constitute about 10% of the elements, and are located on the “staircase” of the periodic table. Metalloids have properties of both metals and nonmetals. </li></ul><ul><li>Physical propertie s: all are solid at room temperature, some have lustre, they tend to behave like nonmetals (except in terms of electrical conductivity), and are semiconductors. </li></ul>Science 10F Unit 2 – Atoms & Elements
  55. 55. Chemical Reactivity Science 10F Unit 2 – Atoms & Elements
  56. 56. Chemical Reactivity <ul><li>When an element, the simplest form of a substance, is involved in forming a new material, a chemical reaction must take place. </li></ul><ul><li>Noble gases all have completely filled outer electron shells and they are unreactive </li></ul><ul><li>When any element has a completely filled outer electron shell, it does not want to react with any other substance. </li></ul><ul><li>  Elements without a completely filled electron shell want to react. It seems that chemical reactivity has something to do with incompletely filled electron shells. </li></ul>Science 10F Unit 2 – Atoms & Elements
  57. 57. Chemical Reactivity <ul><li>The most reactive elements are those in the alkali family, which have one electron in the outer electron shell, and the halogen family, which are one electron short of a filled electron shell. The alkali family needs to lose just one electron to have a filled electron shell and the halogen family needs to gain one electron to have a filled electron shell. </li></ul><ul><li>Chemical reactivity appears to be related to the number of electrons that need to be gained or lost by an element to have its outer electron shell completely filled. The less the number needed, the greater the reactivity of the element. </li></ul><ul><li>The electrons in the outer electron shell are called valence electrons. Valence electrons are involved in any chemical reaction. </li></ul>Science 10F Unit 2 – Atoms & Elements
  58. 58. Chemical Reactivity <ul><li>Chemical reactivity is based on the need for an element to have its outer shell completely filled. Completely filled electron shells in any element will occur when one element combines with another element or another atom of the same element. Three types of activities will provide completely filled energy levels for an element. </li></ul>Science 10F Unit 2 – Atoms & Elements
  59. 59. Chemical Reactivity <ul><li>1. An element can give up one or more electron depending on the family. The alkali metals have one electron only in their outer electron shell. This family will release one electron to another element to achieve a completely filled outer electron shell. For example, sodium will give off one electron to have the same electron configuration as neon, a noble gas which has eight electrons in the outer electron shell. The alkaline earth elements have two electrons in their outer shell. This family will release two electrons to achieve noble gas configuration. For example, calcium will give away two electrons to achieve the same electron configuration as argon. </li></ul>Science 10F Unit 2 – Atoms & Elements
  60. 60. Chemical Reactivity <ul><li>2. An element will take in one or more electrons depending on the family. The halogen family will release one electron to achieve noble gas configuration. For example, chlorine will gain one electron when combining with another element to have the same electron configuration as argon. The chalcogen family will gain two electrons to have the same electron configuration as a noble gas. For example, oxygen will gain two electrons to have the same electron configuration as neon. </li></ul>Science 10F Unit 2 – Atoms & Elements
  61. 61. Chemical Reactivity <ul><li>3. An element will share one or more electrons with another element to form a compound and achieve the electron configuration of a noble gas . </li></ul>Science 10F Unit 2 – Atoms & Elements
  62. 62. What is a compound? <ul><li>An element is the simplest form of any substance. </li></ul><ul><li>An atom is the smallest particle of an element </li></ul><ul><li>A compound is a pure substance made of two or more elements in a fixed proportion. Compounds can be broken down into elements </li></ul><ul><li>A molecule is made of two or more atoms combining to form the smallest particle of a pure substance. Molecules can be broken down into atoms using chemical reactions. </li></ul>Science 10F Unit 2 – Atoms & Elements
  63. 63. What is a compound? <ul><li>Generally, an element contains a large amount of atoms and a compound contains a large amount of molecules. </li></ul><ul><li>Atoms combine to form molecules(elements combine to form compounds) through chemical reactions. </li></ul><ul><li>Molecules or compounds have different properties than the atoms(elements) forming them. </li></ul><ul><li>A chemical reaction involves the moving or sharing of electrons between atoms. </li></ul>Science 10F Unit 2 – Atoms & Elements
  64. 64. Summary Science 10F Unit 2 – Atoms & Elements Element The simplest form of a substance Atom The smallest particle of an element Compound The simplest form of any material containing two or more elements Molecule Two or more atoms joined together chemically - also, the smallest particle of a compound
  65. 65. Chemical Formulas <ul><li>A chemical formula represents the atoms that make up the compound and the proportion in which they combine (e.g., AlCl 3 shows that 1 aluminum and 3 chlorine have combined to form a compound). </li></ul><ul><li>Periodic tables often list the combining capacity of the elements. The combining capacity indicates the number of electrons that are transferred or shared between atoms when they combine. Each family has the same combining capacity. Different families have different combining capacities. The combining capacity of an atom is also called its valence number. </li></ul>Science 10F Unit 2 – Atoms & Elements
  66. 66. Chemical Formulas <ul><li>Chemical formulas describe the number of atoms used to form a single molecule or any number of molecules. Molecules are names that refer to the smallest unit of a compound (e.g., H 2 CO 3 : This formula indicates that 1 molecule of carbonic acid contains 2 atoms of hydrogen, I atom of carbon, and 3 atoms of oxygen. Three molecules of carbonic acid would contain three times as many atoms of each type (6 atoms of hydrogen, 3 atoms of carbon, and 9 atoms of oxygen). </li></ul>Science 10F Unit 2 – Atoms & Elements
  67. 67. Anatomy of a Chemical Formula Science 10F Unit 2 – Atoms & Elements H O 2
  68. 68. Science 10F Unit 2 – Atoms & Elements Chemistry in a Bag
  69. 69. Chemical & Physical Changes <ul><li>Pieces of matter undergo various changes all of the time. Some changes, like an increase in temperature, are relatively minor. Other changes, like the combustion of a piece of wood, are fairly drastic. These changes are divided into the categories of Physical and Chemical change. The main factor that distinguishes one category form the other is whether or not a particular change results in the production of a new substance. </li></ul>Science 10F Unit 2 – Atoms & Elements
  70. 70. Chemical Changes Science 10F Unit 2 – Atoms & Elements
  71. 71. Chemical Changes <ul><li>Chemical change is any change that results in the formation of new chemical substances. At the molecular level, chemical change involves making or breaking of bonds between atoms. To identify a chemical change look for observable signs such as color change, bubbling and fizzing, light production, smoke, and presence of heat. </li></ul>Science 10F Unit 2 – Atoms & Elements
  72. 72. Chemical Changes <ul><li>Some examples of chemical changes are: </li></ul><ul><ul><li>iron rusting (iron oxide forms) </li></ul></ul><ul><ul><li>gasoline burning (water vapor and carbon dioxide form) </li></ul></ul><ul><ul><li>eggs cooking (fluid protein molecules uncoil and crosslink to form a network) </li></ul></ul><ul><ul><li>bread rising (yeast converts carbohydrates into carbon dioxide gas) </li></ul></ul><ul><ul><li>milk souring (sour-tasting lactic acid is produced) </li></ul></ul><ul><ul><li>suntanning (vitamin D and melanin is produced) </li></ul></ul>Science 10F Unit 2 – Atoms & Elements
  73. 73. Physical Changes Science 10F Unit 2 – Atoms & Elements
  74. 74. Physical Changes <ul><li>Physical changes are changes objects undergo which do not change their chemical nature. A physical change involves a change in physical properties. </li></ul><ul><li>Some examples of physical change are: </li></ul><ul><ul><li>whipping egg whites (air is forced into the fluid, but no new substance is produced) </li></ul></ul><ul><ul><li>magnetizing a compass needle (there is realignment of groups (&quot;domains&quot;) of iron atoms, but no real change within the iron atoms themselves). </li></ul></ul><ul><ul><li>boiling water (water molecules are forced away from each other when the liquid changes to vapor, but the molecules are still H 2 O.) </li></ul></ul>Science 10F Unit 2 – Atoms & Elements
  75. 75. Physical Changes <ul><li>Some more examples of physical change are: </li></ul><ul><ul><li>dissolving sugar in water (sugar molecules are dispersed within the water, but the individual sugar molecules are unchanged.) </li></ul></ul><ul><ul><li>dicing potatoes (cutting usually separates molecules without changing them.) </li></ul></ul>Science 10F Unit 2 – Atoms & Elements
  76. 76. Properties of Substances <ul><li>Physical Properties are characteristics that exist in a material. </li></ul><ul><li>State </li></ul><ul><ul><li>The state of a substance – whether it is a gas, a liquid or a solid, is a characteristic property. </li></ul></ul><ul><li>Hardness </li></ul><ul><ul><li>Hardness refers to a materials ability resist being scratched or dented. </li></ul></ul>Science 10F Unit 2 – Atoms & Elements
  77. 77. Properties of Substances <ul><li>Ductility </li></ul><ul><ul><li>Ductility is a measure of the ability of a material to be drawn into a wire. </li></ul></ul><ul><li>Melting point and boiling point </li></ul><ul><ul><li>Melting and boiling points are measurable properties and they are also characteristic of materials. </li></ul></ul><ul><li>Malleability </li></ul><ul><ul><li>Malleable materials are capable of being hammered or rolled into thin sheets. </li></ul></ul>Science 10F Unit 2 – Atoms & Elements
  78. 78. Properties of Substances <ul><li>Viscosity </li></ul><ul><ul><li>Viscosity refers to the ability of a material to flow. </li></ul></ul><ul><li>Solubility </li></ul><ul><ul><li>Some substances such as sugar dissolve easily in water. These substances are called soluble. </li></ul></ul><ul><li>Density </li></ul><ul><ul><li>Density is a measure of a material mass per unit volume. </li></ul></ul>Science 10F Unit 2 – Atoms & Elements
  79. 79. Properties of Substances Science 10F Unit 2 – Atoms & Elements
  80. 80. Properties of Substances <ul><li>Chemical Properties describe the behaviour of a substance as it reacts with another substance to form new materials. Listed below are some characteristic of chemical change. </li></ul><ul><li>When two or more chemicals combine they sometimes burn – that is, they are combustible . An example of combustibility occurs when hydrogen and oxygen combine. A spark will cause them to combine explosively to form water. </li></ul><ul><li>Some substances change colour when exposed to air. Silver will turn black. </li></ul>Science 10F Unit 2 – Atoms & Elements
  81. 81. Properties of Substances <ul><li>Some substances will react with water. Lithium will give off a gas, make sparks and fizz. </li></ul><ul><li>Some materials react with acids. A penny will disappear in nitric acid. </li></ul><ul><li>Some substances react to heat. Whenever you have an egg for breakfast, a chemical reaction activated by heat takes place. The protein in the egg has changed into a different protein that is no longer runny, but solid white. </li></ul>Science 10F Unit 2 – Atoms & Elements
  82. 82. Science 10F Unit 2 – Atoms & Elements QUALITATIVE VS QUANTITATIVE
  83. 83. Chemical Equations <ul><li>A chemical change is always accompanied by a chemical reaction . </li></ul><ul><li>A shorthand method can be used to write a chemical equation that illustrates what happens in a chemical reaction . It is possible to illustrate the process in which carbon dioxide forms a precipitate in limewater (calcium hydroxide). </li></ul>Science 10F Unit 2 – Atoms & Elements
  84. 84. Chemical Equations Science 10F Unit 2 – Atoms & Elements
  85. 85. Chemical Equations <ul><li>The chemical reaction is shown as a chemical equation . The chemical equation shows you many things about the reaction, some of which will be described here: </li></ul><ul><ul><li>The carbon dioxide and the calcium hydroxide on the left side of the equation make up the reactants . In most cases, the reactants are the materials that react together . The calcium carbonate and the water on the right side of the equation are the products . The products are normally the materials that remain after the reaction has taken place . </li></ul></ul><ul><ul><li>Only the chemical names (and/or chemical formulas) of the reactants and products are used. The common names such as limewater and water are not used . </li></ul></ul>Science 10F Unit 2 – Atoms & Elements

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