Science Midyear Exam Review

Science Midyear Exam Review Term One 1. The Atom

Science Midyear Exam Review Term One 2. History of the Atom Not on Midyear

Science Midyear Exam Review Term One 3. Periodic Table

- A row (period) tells us how many shells an element has. - A colum (group) tells us how many valence electrons an element has. Metals are to the left of the staircase, non-metals to the right and metalloids along the staircase. Group 1: Alkali Metals Group 2: Alkaline Earth Metals Group 7: Halogens Group 8: Noble Gases

Science Midyear Exam Review 4. Representing Atoms - Lewis Dot Notation: (Only look at valence electrons) Oxygen: Boron: O B - Rutherford-Bohr Model: Oxygen: 8+ - Simplified Atomic Model Carbon: 6 p+ 2 e- 4 e-

Science Midyear Exam Review 5. Ions An ION is an atom that has become electrically charged by losing or gaining one or more electrons. How do we know whether an atom will gain or lose electrons? They want to become like the noble gases, they want to become stable and have full valence electron shells. P Lithium: 3 p+ 2 e- 1 e- Ion form: 3 p+ 2 e- Oxygen: 8 p+ 2 e- 6 e- 8 p+ 2 e- 6 e- Charge= +1 Charge= -2

Science Midyear Exam Review 5. Ions Oxygen: 8 p+ 2 e- 6 e- 8 p+ 2 e- 6 e- What has happened to a positive ion? a) It has lost electrons b) It has gained electrons c) It has lost protons d) It has gained protons

Science Midyear Exam Review 6. Solutions and Concentration An aqueous solution is a solution with water. (Ex; Water and Salt) 1% = 1 (g or ml) 100 (ml or g) 1 ppm = 1 g 1000L ml L x mg 1 L 1 ppm = OR

6. Solutions and Concentration 3. Analysis of a 25 L sample of well water shows that it contains 6 mg of dissolved arsenic.What is the concentration in ppm of dissolved arsenic? 1% = 1 (g or ml) 100 (ml or g) 1 ppm = 1 g 1000L 1 mg 1 L 1 ppm = OR ml L x Calculate the concentration (g/L) if 30 g are dissolved in 250 ml of solution. 2. What is the PPM concentration if 0.06 g are dissolved in 3000 ml of solution? 120 g/L 20 PPM 0.24 PPM

Science Midyear Exam Review 7. Electrolytes An electrolyte is a substance that allows an electric current to flow through the solution (when it's dissolved in water). Acids: Releases H+ ions. Starts with H Ex: HCl andH2SO4 Bases: Releases OH- ions. Ends in OH Ex: NaOH and Mg(OH)2 Salts: Produced by the chemical bonding of a metal and non-metal. Doesn't start with H, doesn't end in OH Ex: NaClandAgNO

Science Midyear Exam Review 7. Electrolytes: PH PH Scale ranges from 0 to 14 If the PH level is less than 7, the solution is acidic If the PH level is 7, the solution is neutral. If the PH level is greater than 7, the solution is basic. or Basic The difference of one unit between two substances actually indicates that one of the substances is 10 times more acidic than the other. For example, a solution with a pH of 3 is _10__ times more acidic than a solution with a pH of 4. A solution with a pH of 9 is _100_ times less basic than a solution with a pH of 11.

Science Midyear Exam Review 8. Energy Energy a.The Law of Conservation of Energy: Energy cannot be created nor destroyed; it can only be transferred or transformed. b.Energy efficiency: the percent of energy consumed by a machine or system that was transformed into useful energy. Energy efficiency = Amount of useful energy Amount of energy consumed x 100 Example: A fluorescent light bulb uses 100 joules of electrical energy. 25 Joules is light energy, how energy efficient is this light bulb? 25 %

Science Midyear Exam Review 9. Chemical Changes The Law of Conservation of Mass (Matter) The total mass of reactants is always equal to the total mass of products. p.110 Before the reaction After the reaction During CH4 + 2 O2 CO2 + 2H2O 16 g + 64 g 44 g + 36 g C O O H O H H O H O O C H H H H O O Example: Which of the following examples below can be used to verify the Law of Conservation of Mass? a) 5 g + 11 g ---> 12 g + 4 g b) 12 g + 8 g ---> 6 g + 15 g c) 24 g --> 11 g + 13 g

Science Midyear Exam Review 9. Chemical Changes p.110 Example: Which of the following examples below can be used to verify the Law of Conservation of Mass? a) 5 g + 11 g ---> 12 g + 4 g b) 12 g + 8 g ---> 6 g + 15 g c) 24 g --> 11 g + 13 g

Science Midyear Exam Review 10. Types of Chemical Change Acid-Base Neutralization: a chemical change involving the reaction of an acid with a base, producing a salt and water Oxidation: a chemical change involving oxygen (or with properties similar to oxygen) Combustion : a form of oxidation that releases a large amount of energy Cellular-Respiration: a chemical change where glucose and oxygen are used to generate energy, the reaction also produces carbon dioxide and water Photosynthesis: a chemical change that produces glucose and oxygen from solar energy, carbon dioxide and water

Photosynthesis Solar energy + Carbon Dioxide + Water -> Sugar + Oxygen Sugar + Oxygen -> Energy + Carbon Dioxide + Water

Balancing Chemical Equations 1._2___ H 2 + _____ O 2 _2__ H 2 O __2__ H 3 PO 4 _____ H 4 P 2 O 7 + _____ H 2 O

Science Midyear Exam Review 11. Electricity Negatively Charged Bodies: have more electrons then protons Positively Charged Bodies: have less electrons then protons Remember that the number of protons never changes! Substances can only lose or gain electrons. Conductors allow the free flow of electrical charges Insulators hinder the free flow of electrical charges

Science Midyear Exam Review 11. Electricity If A is negatively charged, what charge does C have? If A is positively charged, what charge does D have? Opposite charges attractLike charges repel A B B C A B B C C D

Science Midyear Exam Review 12. Static Electricity Most objects and substances are neutrally charged (same number of protons and electrons) Objects can become positively (+) charged by losing electrons Objects can become negatively (-) charged by gaining electrons Tendency to gain electrons (acquire a negative charge) Tendency to lose electrons (acquire a positive charge) Plastic Nickel Paper Silk Wool Glass What charge will each substance acquire when plastic and wool are rubbed together? Plastic Wool What about wool and glass? Wool Glass

Science Midyear Exam Review 13. Ohm's Law V = IR 1.Find the current through a 12-ohm resistive circuit when 24 volts is applied. 2.Find the resistance of a circuit that draws 0.06 amperes with 12 volts applied. 3.Find the applied voltage of a circuit that draws 0.2 amperes through a 4800-ohm resistance. 2 A 200 Ohms 960 V

How should you prepare for your midyear science exam? 1. Study! R ead through your notes and worksheets, ask yourself questions about what you are reading, explain it to someone else because teaching is a great way to learn. 2. Visit facilelearning L ook through the topics we have covered, answer the questions. Take your time! 3. Get a good night's sleep T eenagers should be sleeping 8.5 to 9 hours a night. Go to bed early, keep yourself energized. 4. Eat well H ave a big and healthy breakfast before your exams. Bring healthy snacks to school.