Science 9

1. Unit 1 Atoms, Elements and Compounds Science 9

2. WHMIS What does WHMIS stand for? • Workplace Hazardous Materials Information System Why do we need WHMIS? • WHMIS is a system of symbols that allows us to see clearly and quickly the potential dangers (hazards) that a chemical can cause. • A chemical container may have one or several symbols on it.

3. WHMIS Symbols Dangerous Container Dangerous Product

4. Textbook • Using your notes and pages 10 and 11 of your textbook, answer questions 1 to 6 on page 15.

5. What’s the Matter? • All fields of science deal with matter. Matter is anything that has a mass and takes up space (i.e. anything that has mass and volume). • We know from last year that volume is the amount of space an object occupies (measured in millilitres or cm3), and mass is the amount of matter in a substance or object (measured in grams). • A substance that is made up of only ONE type of matter is called an element(everything on the periodic table).

6. Properties of Matter • There are two types of properties of matter: physical properties (e.g. What a substance looks like, feels like, if it`s flexible), and chemical properties (e.g. What you can see when a substance reacts with other substances)

7. Physical Properties of Matter • Physical properties fall under two categories, qualitative(things you can observe) and quantitative (things you can measure).

8. Chemical Properties of Matter • Chemical properties let us know how a substance can be used. For example, gold and platinum are made to use jewellery because they don’t react easily with water or air. Trinitotoluene (TNT) is a favourite choice as an explosive because it remains relatively stable when exposed to shocks and vibrations, and does not react with water. There are 3 chemical properties:

9. Textbook • Using your notes and pages 16-19 in your book, answer questions 1, 4, 5, 6, 8, 9, 10, 13 on page 23

10. Lab Safety • Refer to pages 10 and 11 in your textbook. • Watch the Lab Safety Video • Bring your Lab Safety form home for your parents to sign. Even if you had it signed last year, you have to get a new one for this year.

11. Core Lab 1-2C (p. 20) • Read through the procedure on page 20 of your textbook. • Take out a piece of loose-leaf. Write the word “Predictions” on the top of the page. • Copy the table on the next slide on the page:

13. Predictions • Using the table that you just copied, fill in predictions (what you think will happen) for each of the tests that we will perform in the lab. Write your name on the page and hand it in to Ms. Saville.

14. Theories versus Laws • In science, we have theories and laws. There are very important differences between the two: • A law is a way to describe events, relationships or patterns that happen over and over again. • A theory is a way to explain observations that uses reliable evidence. Scientific theories must be testable to be valid. Some theories stand up to every test and become accepted. Others are accepted, but with some exceptions. Still others are rejected because they’ve been proven wrong. • Laws do not explain, and never change. Theories can change when new facts become available (this happened this week with Einstein’s theory of Relativity). • Atomic theory has changed a lot over time as we discover more and more about the structure and function of atoms.

15. Atoms • An atom is the smallest particle of an element that retains the properties of that element. Atoms ARE NOT the smallest or most basic particles. • There are smaller particles called subatomic (below atom) particles called protons, neutrons and electrons. These particles all have mass (i.e. They are made of matter). Protons and electrons have a charge, neutrons do not (i.e. They are neutral).

16. Protons • Protons are found in the nucleus of the atom and have a positive charge (a charge of +1). • Protons are one of the larger subatomic particles, and account for about half of the mass of an atom. • Protons attract electrons because their positive charge attracts the negative charge of the electron. Atoms have an equal number of protons and electrons. • Protons cannot leave the nucleus of the atom under normal circumstances (everyday chemical reactions)

17. Neutrons • Neutrons are also fairly large subatomic particles, and account for almost half of the mass of the atom. The mass of a neutron is slightly higher than that of a proton. • Neutrons are also found in the nucleus of the atom, and cannot leave under normal circumstances (anything other than nuclear fission or fusion) • Neutrons have no charge (a charge of zero) • Neutrons determine the isotope of an atom. Isotopes are different forms of the same atom (i.e. They have the same number of protons and electrons, but different numbers of neutrons). • Carbon, for example, has two isotopes: carbon-12 (6 protons, 6 electrons, 6 neutrons) is the type of carbon you are most familiar with, and is found all over the world. Carbon-14 has 6 protons and electrons, but 8 neutrons. Carbon-14 is radioactive and very rare.

18. Electrons • Electrons are the smallest subatomic particle. Their mass hardly contributes to the overall mass of an atom (they have 1800X less mass than neutrons or protons) • Electrons have a negative charge (-1) • Electrons are not found in the nucleus, but in regions called energy levels around the nucleus (kind of like Saturn’s rings) • The energy levels take up most of the size of the atom (99.99 %). The nucleus itself is tiny (0.01%) in comparison. • Because the electrons are not bound inside the nucleus, this is the part of the atom that reacts with other atoms in chemical reactions.

20. How do we know all this stuff anyway? • Our current understanding of the structure of an atom was developed based on several different atomic theories. Some of these have been adapted based on new information, and others have been discarded completely. We will look at 5 of these.

21. The Early Greeks • There were two Greeks that we remember for attempting to explain matter, Empedocles and Democritus. • Democritus thought that any substance when cut, would eventually be cut into a piece that couldn’t be divided any more (the atomos). • Empedocles thought that all matter was made of four elements (earth, air, wind and water). • Oddly enough, Empedocles’ theory was the most respected of the time. Aristotle agreed with him, and as one of the most respected thinkers of the day, most people went along with what he thought.

22. John Dalton • Dalton said that the particles that make up matter are like small, hard spheres that are different for different elements. • He called the atom the smallest part of the element, and said that all matter is made of atoms. The rest of his theory stated: • Atoms cannot be created, destroyed or divided into smaller particles • Atoms of the same element are identical • Compounds are created when atoms of different elements link together

23. JJ Thomson • Thomson thought that atoms were made of much smaller particles. Through his experiments, he determined that these smaller particles had a negative electric charge (electrons). • His atomic model proposed that an atom looked like a raisin bun – a positively charged ball embedded with negatively charged particles.

24. Ernest Rutherford • Rutherford was Thomson’s student, and designed an experiment to try to discover what was inside atoms. He sent a beam of positively charged alpha particles to a thin sheet of gold. He watched the results from a detector screen around the gold, and saw what happened to the alpha particles. • Most of the alpha particles went through the gold atoms without being affected – this confirmed that there were large spaces within atoms. • What he saw that he was very surprised by was that some of the alpha particles bounced back from the atoms. This was the first discovery of the nucleus. • He later discovered that there were two kinds of particles in the nucleus of an atom, one with a positive charge and one with a neutral charge.

25. Niels Bohr • Bohr was a student of Rutherford and studied the area surrounding the nucleus of an atom. • By passing an electric current through a gas he saw that he could make them glow. He said that this was because they surround the nucleus in specific energy levels. • He discovered that the electrons in each energy level have a specific amount of energy and can jump from one energy level to another.

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27. Review for Quiz • Do all questions under Checking Concepts and Understanding Key Ideas on pages 34 and 35 except for: • # 2, 5, 6, 16, 20 and 21.

28. Elements • Remember from the last section, and element is a pure substance that can’t be broken down or separated into other substances. Each element is made of one type of atom (e.g. a lump of pure gold is made of only gold atoms). • There are 115 elements (92 are found in nature). Each is represented by a chemical symbol.Chemical symbols consist of one or two letters. The first letter is ALWAYS capitalized. The second letter is not.

29. The Periodic Table

30. The Periodic Table • Divided into 4 sections – Metals (to the left of the staircase), Nonmetals (to the right of the staircase), Metalloids, and Transition Metals. • There are two liquids and 11 gases on the periodic table, all of the rest are solids.

31. Activity • Using the periodic table (p. 50), list the first twenty elements (Go by the atomic number), their state at room temperature, and their chemical symbol. • Put this list in your portfolio when you are finished.

32. Elements You MUST Know • For this course, you are responsible for knowing the names and chemical symbols for the following elements: (i) Hydrogen (ii) Sodium (iii) Potassium (iv) Magnesium (v) Calcium (vi) Iron (vii) Nickel (viii) Copper (ix) Zinc (x) Carbon (xi) Nitrogen (xii) Oxygen (xiii) Neon (xiv) Helium (xv) Chlorine (xvi) Silicon (xvii) Silver (xviii)Gold (xix) Mercury (xx) Lead

33. Atomic Number VS Atomic Mass • The atomic number is the number of protons in the nucleus of an atom. • The atomic mass is the mass of the average atom of an element (mass of protons and neutrons usually)

35. Questions in Textbook Answers questions p.59 1, 2,4, 5, 6, 9, 10, 11, 12, 13, 14, 15, 25

36. Elements are divided into 4 groups on the periodic table Each family on the periodic table has specific properties: • Metals are shiny, ductile, good conductors of heat and electricity, and malleable. • Transition metals have all of the same properties as metals, however their electrons are arranged differently in the energy levels around the atom. • Non-metals are dull, poor conductors of heat and electricity, brittle, and not ductile. • Metalloids can by shiny or dull, can conduct electricity, are poor conductors of heat, and are brittle and not ductile.

37. Period and Family • Period: the horizontal (sideways) rows on the periodic table, numbered from 1 to 7. The higher the period # the higher the reactivity of the element in a given family. • Family: also called group. Elements in the same family have the same chemical properties. Families are in vertical columns on the periodic table (1-18).

38. Chemical Families There are 4 chemical families: • Alkali metals: column 1 besides hydrogen. All of the alkali metals are very reactive. Elements at the top of the column are less reactive than elements at the bottom. • They react strongly with water and oxygen, and combine with nonmetals to make chemical compounds. All of the alkali metals melt below 200oC, and all are soft enough to be cut with a knife. • Alkaline earth metals: column 2. These are less reactive than alkali metals. They will burn in the air if they are heated (remember magnesium from the lab). They will react with water, but not as explosively as alkali metals.

39. Chemical Families continued • Halogens: these are non-metals. They react very well with metals and other compounds. They are found in column 17. • Noble gases: these are found in column 18. Noble gases are not reactive because they have full energy levels. Some glow in bright colours (neon).

41. p. 67 • Answer all questions except for number 12. • When it says to do a Bohr-Rutherford diagram, draw a modified Bohr diagram.

42. Chemical Compounds • Chemical compounds are pure substances made of two or more kinds of elements that have chemically combined. When they combine, atoms form bonds with one another. There are two types of bonds, ionic bonds and covalent bonds.

43. Ionic Bonds • Ionic Bonds occur when oppositely charged ions attract together.That is, when a metal and one or more non-metals come together. This is because metal ions are always positively charged (lose electrons), and non-metal ions are always negatively charged (gain electrons). • You will be responsible for knowing the following ionic compounds: • sodium chloride (table salt): NaCl • calcium carbonate (chalk): CaCO3 • sodium hydroxide (a strong base): NaOH

44. Naming Ionic Compounds • When naming simple ionic compounds, the metal name remains the same, and the non-metal name is changed to end in “ide”. • For example, sodium and chlorine combine to form sodium chloride… you drop the “ine” and replace it with “ide”. • The name of the metal ALWAYS goes first!

45. Covalent Bonds • Covalent bonds are different from ionic bonds. In ionic bonds, atoms gain or lose electrons. In covalent bonds, atoms share electrons to form a molecule. Molecules are made from nonmetal atoms coming together. • You will be responsible for knowing the formulas and names of the following covalent molecules: • sucrose (table sugar): C12H22O11 • carbon dioxide (what you breathe out): CO2 • methane (what cows fart out): CH4 • water (what you should drink instead of Gatorade): H2O

46. Naming Covalent Compounds • Naming covalent compounds is more difficult than naming ionic compounds • First, name the first element in the compound. • Second, if there is more than one of the 1st element, add in the prefix for that number • Third, name the second atom and switch the end out for “ide” • Fourth, add a prefix to the second atom based on how many of it there are: • 1 - mono 6 - hexa 2 - di 7 - hepta 3 - tri 8 - octa 4 - tetra 9 - nona 5 – penta 10 - deca • Then write the full name of the compound. For example, let’s look at NO3. N is nitrogen. O is oxygen, but will be changed to “oxide”. There are 3 oxygen atoms, so the entire name of the molecule will be nitrogen trioxide. • And now, a song.

47. p. 85 • Questions 1 to 8, EXCEPT #4

48. Notebook Activity • Read pages 88 and 89 in your book. • In your notebook: • Define physical and chemical change. Give two examples of each. • Define reactants and products. • Draw a table similar to the one below (about half a page in your book): • Define/describe each type of evidence in your table (you can use words or pictures or both) • In a chemical change, are elements or compounds conserved? What does this mean?

49. Chemical vs Physical Changes

50. Combustion • Read page 89 in your textbook. • Define combustion • What type of energy is released during combustion? Give two examples of how this energy can by used directly and two examples of how it can be used indirectly (make sure to include what the energy is changed into).