WORKSHEET 1 REVIEW OF GRADE 9 CHEMISTRY

Transcription

1 WORKSHEET 1 REVIEW OF GRADE 9 CHEMISTRY PART A: DEFINITIONS/THEORY Matter: is anything that has mass and takes up space. -Matter can be classified according to its composition, ex. a mixture or a pure substance -Matter can be described using physical and chemical properties -Matter can undergo a physical or chemical change Pure Substance: a substance in which all particles making up the substance are the same An element is a pure substance that is made of atoms and thus cannot be broken down into simpler substances. ex. gold, carbon, hydrogen, etc. (see periodic table of elements) A compound is a pure substance that is made of two or more atoms combined in a fixed proportion. ex. H 2O (is always 2 hydrogen and 1 oxygen) ex. CO 2 (is always 1 carbon and 2 oxygen) Mixture: a substance in which there are two or more types of particles -mixtures can be homogeneous or heterogeneous A homogeneous mixture is a mixture in which the particles are uniformly scattered. Only one phase is visible. (ex. solutions such as Kool-Aid) A heterogeneous mixture is a mixture in which the particles are not uniformly scattered and therefore have more than one phase. (ex. oil and water) MATTER MIXTURES PURE SUBSTANCES HOMOGENEOUS HETEROGENEOUS ELEMENTS COMPOUNDS MIXTURES MIXTURES SOLUTIONS ORDINARY SUSPENSION EMULSION MECHANICAL MIXTURE

2 Physical Property: a characteristic or description of a substance, observed using your senses (ex. physical state, colour, odour, taste, clarity, lustre, crystal shape, texture, hardness, brittleness, ductility, viscosity, density, freezing point/boiling point, electrical conductivity, malleability, specific heat capacity) **some physical properties are qualitative while others are quantitative** Chemical Property: a characteristic of a substance that describes its ability to react with other substances (ex. reaction with water/acid/oxygen, combustibility, toxicity, stability) Physical Change: involves a substance changing in terms of its physical properties, no new substances are formed and the change may be reversible (ex. freezing water, dissolving salt in water, mixing oil and water) Chemical Change: involves a change in matter in which at least one new substance, with new properties, is formed. -There are five clues that indicate a chemical change may have occurred: new colour, heat or light is produced, bubbles of gas are formed, a precipitate forms, difficult/impossible to reverse PART B: ATOMIC STRUCTURE Elements are pure substances, made up of only one type of atom. Elements are organized in the Periodic Table (see front page). Within an atom there are 3 kinds of subatomic particles: a) protons: -carry a positive charge (+) -are located in the central nucleus -the number of protons is the same as the atomic number b) neutrons -no charge, neutral (N) -are located in the central nucleus c) electrons -carry a negative charge (-) -orbit around the nucleus in electron shells -the valence electrons are the electrons in the outermost (valence) shell **An atom has an equal number of protons (+) and electrons (-) so that the overall charge is zero.**

3 Diagram of an Atom nucleus N + N + + N + N N + N + Electron shells ACTIVITY #1: Diagram of an Atom What type of atom is shown in the diagram above? (HINT: Count the number of protons (remember this is atomic #) and check the periodic table) ACTIVITY #2: Find the numbers of subatomic particles Rules: 1. Atomic number = number of protons 2. Mass number = number of protons + number of neutrons (mass number can be found in the periodic table by rounding the atomic mass) 3. Number of protons = the number of electrons (in a neutral atom) Element Symbol Atomic Number Mass Number # of protons # of electrons # of neutrons Oxygen Mn Barium Fe

4 ACTIVITY #3: Standard atomic notation 19 F 9 This notation tells us that fluorine has protons and 19-9 = neutrons. Write standard atomic notation for the following atoms: a) nitrogen b) sulfur c) calcium PART C: ORGANIZATION OF THE PERIODIC TABLE The periodic table is organized in several ways: a) according to atomic number b) it is divided into 18 columns called families or groups Group 1 = alkali metals Group 2 = alkaline earth metals Groups 3 12 = transition metals Group 17 = halogens Group 18 = noble gases c) by metals, non-metals, metalloids d) it is divided into 7 periods (rows) ACTIVITY #4: Periodic Table a) There are 32 elements not named on the periodic table at the front of this package. Fill in the names on the table. b) Using the periodic table in your textbook, colour your periodic table so that it is divided into three sections (metals, non-metals and metalloids). Don t forget to colour in the legend. c) Neatly label the names of the groups/families on your periodic table. d) List the elements found in period 3: e) How many valence electrons do the atoms in group 1 have? f) How many valence electrons do the atoms in group 2 have? g) How many valence electrons do the atoms in group 13 have? h) How many valence electrons do the atoms in group 17 have? i) How many valence electrons do the atoms in group 18 have?

5 j) What is a full valence shell called? k) How many shells (orbits) do the atoms in period 1 have? l) How many shells (orbits) do the atoms in period 2 have? m) How many shells (orbits) do the atoms in period 3 have? ACTIVITY #5: Elements and their symbols Complete the following chart: Name Symbol Name Symbol Boron He Manganese Platinum Bromine Aluminum Nickel Lithium Hydrogen P I Hg Ag Co Zn Si PART D: MODELS OF ATOMS Bohr Model of the Atom (Bohr Diagrams) A circle is drawn in the middle to represent the nucleus. The element symbol is placed in the middle of the circle. B A series of circles is drawn around the nucleus to represent the shells (orbits). Electrons are shown in these shells. **NOTE: a maximum of two electrons in the first shell a maximum of eight electrons in the second shell a maximum of eight electrons in the third shell B

6 ACTIVITY #6: Bohr Diagrams Draw Bohr diagrams for the following atoms: hydrogen carbon magnesium calcium Bohr-Rutherford Models of the Atom (Bohr-Rutherford Diagrams) A circle is drawn in the middle to represent the nucleus. The number of protons and neutrons is placed in the middle of the circle. 5P 6N boron Electrons are once again shown in shells (orbits) around the nucleus. 5P 6N ACTIVITY #7: Bohr-Rutherford Diagrams Draw Bohr-Rutherford diagrams for the following atoms: hydrogen carbon magnesium calcium Lewis Dot Diagrams Write the symbol of the element. N

7 Place dots (representing VALENCE electrons) around the element symbol. **NOTE: dots should be paired up and there should NEVER be more than eight** **NOTE: there should be an electron on all four sides before pairing** N ACTIVITY #8: Lewis Dot Diagrams Draw Lewis Dot Diagrams for the following atoms: hydrogen carbon magnesium calcium PART E: COUNTING ATOMS How to count atoms: 1. The symbol of an element (without a subscript) in a compound always represents one atom of that element. Ex. Na = 1 sodium atom NOTE: a subscript is a number written at the lower right corner, after the symbol of an element 2. If there is more than one atom of the element, then a subscript is used to indicate the number of atoms. Ex. H 2 = 2 hydrogen atoms 3. A subscript outside a bracket multiplies all the elements INSIDE the brackets. Ex. Mg 3(PO 4) 2 = 8 oxygen atoms 4. a) A coefficient is a number written in front of a chemical symbol and indicates the number of atoms of that element. Ex. 3 C = 3 carbon atoms b) The coefficient multiplies the number of atoms of EACH element in the formula. Ex. 2 H 2O = 4 hydrogen atoms and 2 oxygen atoms Ex. 3 CuSO 4 = 3 copper atoms, 3 sulfur atoms, 12 oxygen atoms

8 ACTIVITY #9: Counting Atoms Complete the following tables: KMnO 4 K 2CrO 4 NH 4C 2H 3O 2 2 (NH 4) 2Cr 2O 7 Pb(NO 3) 2 Zn 3(PO 4) 2 3 C 6H 12O 6 2 Ca(Cr 2O 7) 2 3 BaCl 2 4 Al 2(CO 3) 3

9 PART F: IONS Atoms want to achieve stability by either filling their valence shell or completely emptying it. This is the whole basis for why atoms either gain or lose electrons and become charged ions (an atom with a charge = an ion). Therefore an ion is formed when atoms have an unequal number of protons and electrons (charge is no longer zero). If an atom gains an electron, it becomes a negatively charged ion (this is called an anion). If an atom loses an electron, it becomes a positively charged ion (this is called a cation). ACTIVITY 10: Ions 1. a) What is the charge of an ion that has 11 protons and 10 electrons? b) What is the name of this ion? 2. a) What is the charge of an ion with 15 protons and 18 electrons? b) What is the name of this ion? ACTIVITY #11: Drawing Ions Draw the Bohr-Rutherford Diagram AND the Lewis Dot Diagram for the chlorine atom: a) How many electrons does chlorine need to form a stable outer shell? b) What is the total number of electrons after forming a stable octet? c) What is the total number of protons after forming a stable octect? d) What is the overall charge of chlorine? e) Draw the Bohr-Rutherford Diagram for the chlorine ION (HINT: don t forget to include the charge!) f) Draw the Lewis Dot Diagram for the chlorine ION (HINT: don t forget to include the charge!) g) Draw the Bohr-Rutherford Diagram AND the Lewis Dot Diagram for the following ions: i) oxygen ii) magnesium