June Exam Review Material World

Transcription

1 Review Problems for Science & Technology June Exam Chapter on Atoms and Elements MATERIAL WORLD UIT 1. Which of the following is true about Sodium? a) It is an Alkali Metal b) It is an Alkaline Earth Metal c) It is a Halogen d) It is a oble Gas 2. Which of the following is FALSE about the Rutherford-Bohr diagram of Phosphorus? a) It has 15 protons b) It has 15 neutrons(most isotopes will have = 15 neutrons) c) It has 15 electrons d) It has 5 valence electrons 3. Which of the following is TRUE about fluorine s Rutherford-Bohr diagram? a) It has 1 energy level b) It has 7 valence electrons c) It has 17 electrons d) It has 19 electrons 4. Which of the following Rutherford-Bohr diagrams is correct for Argon? D (for the ST exam, know that a neutron is neutral, but they will only ask you to place protons in the nucleus, not neutrons. See check list if you don t believe me.) a) b) 18 p + 40 n 0 20 e 20 e 2 e 9 e 10 e c) d) 18 p + 40 n 0 18 p + 21 n 0 18 p + 22 n 0 2 e 8 e 8 e 2 e 8 e 8 e

2 5. Which of the following is the correct Lewis diagram for Carbon? B (you have to pair electrons; remember to use last shell electrons only) a) b) C C c) d) C C 6. Which of the following is the correct Lewis diagram for Mg? A a) b) Mg Mg c) d) Mg Mg 7. Which of the following is the Alkali metal in the 3 rd period? a) Sodium b) Sulphur c) Magnesium d) Calcium 8. Which of the following is the Halogen in the 2 nd period?

3 a) Fluorine b) Chlorine c) eon d) Argon 9. Which of the following is true about the periodic table? a) The period indicates the number of neutrons that an atom has b) The Group number indicates the number of electrons that an atom has c) The period indicates the number of protons that an atom has d) The Group number indicates the number of valence electrons that an atom has 10. Which of the following is ALWAYS true about the periodic table? a) The number of protons is equal to the number of electrons (if the atom is neutral; otherwise e= p c, where c = charge) b) The number of protons is equal to the number of neutrons c) The number of electrons is equal to the number of neutrons d) The number of valence electrons is equal to the number of protons 11. Where in the periodic table can you find the following: a) an alkaline earth metal? 2 nd column b) a noble gas? Last column c) a halogen? 2nd last column d) a metal? To the left of staircase; exception H and most of the ones touching(metalloids) e) an atom containing only one electron shell? Ist row(h and He only)

4 12. Two elements X and Y have the following properties. Element X Element Y Metallic luster Without metallic luster Two valence electrons Four valence electrons Located in the 4 th period 6 protons Which symbols from the periodic table correspond to elements X and Y respectively? A) Ca and C B) K and B C) K and C D) Ca and B 13. Which of the following statements about the properties of metals is correct? A) They are malleable but are not shiny. B) They conduct electricity but are not malleable. C) They do not conduct electricity and are not shiny. D) They react with acids and conduct heat. 14. The following diagram represents the Bohr-Rutherford model of an element. Which of the following is true? A) The element is located in period 1 and is an alkaline earth metal. B) The element is located in period 1 and is an alkali metal. C) The element is located in period 2 and is an alkali metal. D) The element is located in period 2 and is an alkaline earth metal. 15. Four elements from the periodic table are described below. Element A: It reacts vigorously with water and its electrons are distributed among three energy levels. Element B: It is located in Period 3 and used to disinfect or to kill bacteria. Element C: Its electron configuration is

5 Element D: Its outermost energy level is full and it could have 22 neutrons. Complete the table below by indicating the chemical symbol and the name of the chemical family for each of these elements. Element Chemical Symbol Chemical Family ame Element A a Alkali metal Element B Cl halogen Element C Mg Alkaline earth Element D Ar oble gas 16. Which of the following states two properties of the elements in the halogen family? A) They are soft metals and highly reactive. B) They do not conduct electricity and are not shiny. C) They conduct electricity but are less reactive than alkali metals. D) They are colourless in their natural state and are not chemically reactive 17. An element has the following characteristics: It has a metallic luster. It conducts electricity. It has 3 valence electrons. It is a metal What is this element? A) Aluminum B) Lithium C) Silicon D) Sodium

6 18. The table below gives the chemical symbols of four elements and provides space to indicate the following characteristics: the number of valence electrons, the number of energy levels, chemical reactivity (none, low or high) and the family number. Using the periodic table, fill in the blank boxes in the table. Li C Cl e 1 valence 2 levels 7 valence; 3 levels not reactive; VIII

7 19. Listed below are items of information pertaining to the Rutherford-Bohr model of an atom of a chemical element. 1-The number of positive charges 2- The number of negative charges 3-The number of electron shells (energy levels) 4-The number of valence electrons 5-The atomic number Which table correctly indicates the items of information pertaining to the inside and outside of the nucleus? A) Inside the nucleus Outside the nucleus 1, 3 and 4 2 and 5 B) Inside the nucleus Outside the nucleus 1 and 5 2, 3 and 4 C) Inside the nucleus Outside the nucleus 2, 3 and 5 1 and 4 D) Inside the nucleus Outside the nucleus 2 and 4 1, 3 and 5

8 Chapter on Molecules and Solutions 20. When Chlorine becomes an ion, what is its ionic notation? a) Cl c) Cl b) Cl 2 + d) Cl When Sodium becomes an ion, what is its ionic notation? a) a b) a + c) S 2 d) S When Aluminum becomes an ion, what is its ionic notation? a) Al 3 b) Al 3+ c) Al 13 d) Al When eon becomes an ion, what is its ionic notation? a) e b) e + c) e 8 d) one of the above

9 24. Draw the Rutherford-Bohr AD the Lewis model for the following ions: a) a + b) 3- c) B 3+ a + : 11p 2e)8e) 3-7p 2e)8e) B 3+ 5p 2e) 25. A student makes 75 ml of a 12.5 g/l salt solution. How much salt was used? m = CV = 12.5g/L (0.075 L) = a) 0.17 g b) 0.94 g c) 6 g d) 937 g

10 26. A salt solution has a concentration of 6.1 % m/v. Which concentration below does this equate to? 6.1 % m/v means 6.1 g/100 ml = 6100 mg/0.1 L = ppm a) 0.61 g/ml b) 0.61 g/l c) 6.1 g/l d) ppm 27. A C 6 H 12 O 6 solution has a concentration of 215 ppm. Which concentration below does this equate to? 215 ppm means 215 mg/l = g/l a) g/ml b) g/l c) % m/v d) 2.15 % m/v 28. A KOH solution has a concentration of 0.05 g/ml. Which concentration below does this equate to? 0.05 g/ml = 50 mg/0.001 L = ppm To get %, we need to know how much would be in 100 ml = 0.05 g /ml *100 ml = a) 5 % m/v b) 50 ppm c) 500 g/l d) 5000 ppm By the way, 0.05g/L is also equal to 50 g/l. Show why.

11 29. Matthew has 4 different salt solutions. Solution A has a concentration of g/ml = 3.4mg/0.001L = 3400 ppm Solution B has a concentration of 0.4 g/l = 400 mg/l = 400 ppm Solution C has a concentration of 0.42 % m/v = 0.42 g/100 ml = 420mg/0.1 L = 4200 ppm Solution D has a concentration of 435 ppm Which one has the highest concentration? a) Solution A b) Solution B c) Solution C d) Solution D 30. Sophie also has 4 different salt solutions. Solution A has a concentration of g/ml Solution B has a concentration of 0.4 g/l Solution C has a concentration of 0.42 % m/v Solution D has a concentration of 435 ppm Which one has the lowest concentration? a) Solution A b) Solution B c) Solution C d) Solution D 31. Alex has 4 different aoh solutions. Solution A has a concentration of 0.2 g/ml Solution B has a concentration of 19 g/l Solution C has a concentration of 2.1 % m/v Solution D has a concentration of ppm

12 Which list correctly places the solutions from least to most concentrated? a) A, C, D, B b) A, C, B, D c) B, D, C, A d) B, D, A, C

13 32. Many commercial products are aqueous solutions. a) A variety of orange juice contains 26g of carbohydrates per 250 ml serving. What is the concentration of carbohydrates in % m/v? 26g/250 ml *100% = 10.4% b) A 500mL bottle of isopropyl alcohol, better known as rubbing alcohol, contains 350 ml of alcohol. What is the alcohol concentration in % v/v? 350g/500 ml *100% = 70% 33. During a lab experiment, you are asked to prepare 200 ml of a 12% m/v saltwater solution. Describe a procedure that will allow you to make the solution. 200 ml * 12g/100 ml = 24 g 1. Weigh 24 g of saltwater 2. Dissolve in a beaker of water 3. Transfer to a 200 ml volumetric flask. 4. Add water to line and mix.

14 34. Alice frequently uses a white cleaning powder in her home. She wants to know whether this substance is acidic, basic or neutral. In order to determine the ph of this substance, what is the first thing that she must do? A) Put a piece of blue litmus paper on the solid. B) Put a piece of red litmus paper on the solid. C) Verify whether the substance conducts electricity. D) Dissolve a small amount of the solid in water. 35. Which of the following are acids? 1. acl 2. HCl 3. LiF 4. H 4 OH 5. HI 6. HCH 3 CO 2 7. KOH 8. CaCl 2 A) 1, 5, and 8 B) 2, 5, and 6 C) 5, 6, and 8 D) 3, 4 and 7

15 36. Which of the following are bases? 1. aoh 2. HCl 3. LiF 4. H 4 OH 5. BeO 6. HI 7. KOH 8. CaCl 2 A) 1, 4, and 7 B) 2, 3, and 8 C) 3, 5, and 6 D) 1, 3, and Which of the following describes a neutral salt? A) A solution that does not conduct electricity and that does not change the colour of litmus paper. B) A solution that does conduct electricity and that does not change the colour of litmus paper. C) A solution that does conduct electricity and turns litmus paper red. D) A solution that does conduct electricity and turns litmus paper blue.

16 38. Use the table below to determine which statement is TRUE. A) When a strong acid is used with indicator 1, the solution turns blue. B) A neutral solution will be colourless when indicator 2 is used. C) When a strong base is used with indicator 3, the solution turns red. D) When the solution is a weak acid and indicator 4 is used, the solution turns red. 39. Scientific studies show that the number of aquatic species declines when a lake becomes more acidic. The ph of the water in four lakes was measured to determine whether aquatic species are threatened. The table below lists the ph values obtained: Lake ph Which of these lakes poses the greatest threat to aquatic species? A) Lake 1 B) Lake 2 C) Lake 3 D) Lake 4

17 40. In order to classify three unknown solutions as acids, bases or salts, you have been given the following information: Solution information Electrical conductivity yes yes Yes Reaction of blue litmus paper Turns red Stays blue Stays blue Reaction of red litmus paper Stays red Stays red Stays blue On the basis of this information, how do you classify the three solutions? A) Solution 1: Acid Solution 2: Base Solution 3: Salt B) Solution 1: Acid Solution 2: Salt Solution 3: Base C) Solution 1: Base Solution 2: Acid Solution 3: Salt D) Solution 1: Base Solution 2: Salt Solution 3: Acid 41. A solution of aoh is tested, and its ph is recorded. Which product below could be used to neutralize this solution? a) HCl b) Mg(OH) 2 c) acl d) H 2 O 42. Which of the following ph values is alkaline? a) 5 b) 6 c) 7 d) An apple has a ph of 3, and a carrot has a ph of 5. How many times is the apple more acidic than the carrot? 5-3 = 2, so apple is 10 2 = 100 times more acidic.

18 44. To check the electrical conductivity of certain liquids, a student used a conductivity apparatus equipped with a light bulb. Using the table of information, determine which substances are electrolytes. Substances HCl CH 3 OH MgCl 2 aoh Ca(OH) 2 CCl 4 Observations Bright light o light Faint light Bright light Faint light o light A) CH 3 OH and CCl 4 B) CH 3 OH, aoh and Ca(OH) 2 C) HCl, MgCl 2 and CCl 4 D) HCl, MgCl 2, aoh and Ca(OH) In a neutralization reaction: A) two acids react to form water. B) water and a salt react to form an acid and a base. C) an acid and a salt react to form water and a base. D) an acid and a base react to form a salt and water.

19 46. Complete the following dissociation equation and label each as either acid, base or salt. a) HCl H + + Cl - type of electrolyte:_acid b) Mg(OH) 2 Mg OH - type of electrolyte: base c) BCl 3 This gas won t break up into ions in water; it reacts instead. 47. a) A student has to choose a test in order to distinguish whether a solution is an acid, base or salt. He chooses the electrical conductivity test. Describe why this would (or would not) be an appropriate test. Bad test. All of the above conduct electricity in solution, so it won t help you distinguish between them. b) Complete the neutralization reaction: aoh + HO 3 ao 3 + H 2 O

20 Chapter on Different Forms of Energy 48. What is the law of conservation of energy? Energy can be transformed from one form into another, but it cannot be created or destroyed. 49. Wind turbines generate power for all communities in Texas. How does a wind turbine transform energy? The wind spins the blades of a turbine which through a gearbox spin the magnets of a generator When these move, alternating current electricity in copper coils within the core starts to flow. 50. What energy transformation takes place in a flashlight that uses batteries? Chemical to electrical to light energy.

21 51. What is the percent efficiency of a light bulb that is supplied with 2000 J of energy and 300J is used to give off light? 100% % = 85% 52. A television takes 1000 J of energy and gives off 150J as heat. What is the percent efficiency of the television? % = 85% A hummer uses 5000 J of energy and 3000 J is given off as pollution while the rest is converted to mechanical energy to make the car move. What is the percent efficiency of the hummer? 40%

22 54. A student is heating two beakers of water. In beaker A, there is 500 ml of water at 50⁰C while beaker B contains 100mL of water at 100⁰C. In which beaker is the heat energy the greatest? Explain your answer. Beaker A Beaker B Answer: beaker A It s a bit of an unfair question that goes beyond the scope of the course. Although heat depends on both mass and temperature(part of the course), and although there is 5 times as much mass at 50 o C, 100 o C does not represent twice the kinetic energy of molecules. To figure that out, you need to convert to the Kelvin scale by adding 273. So at 100 C, there is only 373/323 times as much movement but only 1/5 th of the mass, so there is less heat in beaker B. 55. Julia goes jogging three times a week. On those days, she eats two slices of whole wheat bread with oatmeal and a glass of milk. She completes her meal with a piece of fruit, often an apple. An hour after her meal, she runs 12 km. a) What form of energy is contained in these foods? chemical b) What form of energy is the source of the energy stored in the food Julia eats? solar

23 c) As Julia runs, the energy from the food is transformed into other forms of energy. ame these other forms of energy and explain your answer. Heat, mechanical energy and other forms of chemical energy as the food compounds are converted into other molecules. Chapter on Changes in Matter 56. Consider the following chemical reaction: 2 acl + Ca(OH) 2 CaCl 2 +2 aoh If the mass of acl reacted is 191 grams and that of Ca(OH) 2 is 74 grams then 80 grams of aoh is produced. What mass of CaCl 2 is produced? = 185 g, but this question is badly constructed because they are not reacting in stoichiometric ratios. It should have read: If the mass of acl reacted is 191 grams and that of Ca(OH) 2 is 120 grams then 130 grams of aoh is produced. What mass of CaCl 2 is produced? The answer would have been = 181 g

24 57. Which part of the triangle of fire are firefighters tackling in each of the following situations? Explain your answers. a) Firefighters at an airport pour foam onto a pool of flammable liquid spilled by an airplane in distress. The fire is being choked so the oxidizer(often oxygen) is being removed. b) Firefighters spray water onto the roofs and sides of two houses next to a blaze. Heat d) During a forest fire, firefighters begin clear-cutting a threatened area. They cut a 50-m-wide stretch of forest a few kilometres ahead of the fire. Fuel is being eliminated. 58. Which of the following is the chemical formula for respiration? a) C 3 H 8 + 5O 2 3CO 2 + 4H 2 O b) C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O c) 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 d) 3CO 2 + 4H 2 O C 3 H 8 + 5O Which of the following is a combustion chemical equation? a) C 3 H 8 + 5O 2 3CO 2 + 4H 2 O b) C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O c) 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 d) 3CO 2 + 4H 2 O C 3 H 8 + 5O 2

25 60. Which of the following is the chemical formula for photosynthesis? a) C 3 H 8 + 5O 2 3CO 2 + 4H 2 O b) C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O c) 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 d) 3CO 2 + 4H 2 O C 3 H 8 + 5O During a chemical reaction, 15 g of hydrochloric acid (HCl) reacts with 3.7 g of aluminum (Al) to produce 18 g of aluminum chloride (AlCl 3 ) and some hydrogen gas (H 2 ) is released. The balanced equation for this reaction is as follows: 6 HCl + 2 Al 2 AlCl H 2 What mass of hydrogen gas was released? = 0.7 g of hydrogen. 62. Balance the following chemical equations and draw a particle model for each. a) C 6 H 12 O O 2 6 CO H 2 O b) O O

26 + c) CO KOH K 2 CO 3 + H 2 O d) 2 Al + 3H 2 SO 4 Al 2 (SO 4 ) 3 + 3H 2 e) 2 H 2 O 2 2H 2 O + O 2 f) H 4 O H 2 O

27 Chapter on Electricity and Magnetism 63. Which object would be most attracted to the object to the right? D a) b) + c) d) A wire is attached to a 20V power source. An ammeter reads a current of 5A. What is the resistance of the wire? V = IR R = V/I = 20/5 = 4 Ω a) 0.25 Ω b) 25Ω c) 4Ω d) 100Ω 65. A wire with a resistance of 90 Ω is hooked up to a 9 V battery. What current will it draw? a) 810 A b) 99A c) 10A d) 0.1A 66. An appliance draws 4A of current when it is attached to a 20V battery. It is used for 1 minute. How powerful is the appliance? P = VI = 20(4) = 80 W a) 5Ω b) 80 W c) 80J d) 4800 J

28 67. A lamp is plugged into a 100V outlet, and has a resistance of 20Ω. It is on for 30 minutes. How powerful is the lamp? V=IR I = V/R = 100/20 = 5 A P=VI =100(5) = 500 W a) 5A b) 500 W c) 2000W d) J 68. A wire is attached to a variable power source, and the potential difference and current readings are shown below. Current (A) Potential difference (V) a) What is the value of the resistance of this wire? (show your work) conductance = slope = I = 8 2 = 6 V resistance = = 15/6 =2.5 Ω conductance b) How conductive is the wire? (show your work) conductance = slope = I V = = 6 15 S

29 c) If this same wire were attached to a 100 V power source, what current would flow through the wire? (show your work) V=IR 100=I(2.5) A I = 40 A (huge!) Current (A) B 69. Which of the following wires is the best conductor? a) A b) B c) C d) D C D Potential difference (V) 70. A radio uses 4 x 1.5 V batteries and draws a current of 10A. If the radio is used for 5 minutes, how much energy does it use? P = VI = (4*1.5 J/C)(10 C/s) = 60 J/s or 60 W E = Pt = 60J/s(300 s) = J a) 15W b) 60 W c) 300J d) J 71. An oven is plugged into a 200V outlet and has a resistance of 100Ω. It is used for 1 hour. How much energy does it use? a) In Joules? E = VIt = (V 2 /R)t = /100* 3600s = J

30 b) In kw h P=V 2 /R = /100 = 400W = 0.400kW E = Pt =0.400 kw* 1 h = kwh 72. Which of the following does OT affect the conductance of a wire? a) Length of the wire b) Material of the wire c) Potential difference across the wire d) Thickness of the wire Voltage affects the current but not its conductance 73. Given this circuit: L 2 S 1 L 1 S 2 Which switch(es) would have to be on to turn L 1 on? a) S 1 only b) S 2 only c) Both S 1 and S 2

31 d) L 1 will be on without either switch being on. 74. Given this circuit: A L 2 S 1 C L 1 S 2 B Where would you add another switch to allow you to turn L2 on or off without affecting L1? a) A b) B c) C d) one of the above

32 75. Given this circuit: Which of the following statements is TRUE? a) When S 1 is on and S 2 is off, L 2 will go on. b) When S 1 is off and S 2 is on, L 1 will go on. c) When S 1 is on and S 2 is off, L 1 will go on. d) When S 1 is on and S 2 is off, neither light will go on. 76. Given this circuit: What will happen when S1 is closed and S2 is open? a) L1 will be on and L2 will be off b) L1 will be off and L2 will be on c) Both lights will be on d) Both lights will be off

33 77. Given this circuit: What will happen when S1 is open and S2 is closed? a) L1 will be on and L2 will be off b) L1 will be off and L2 will be on c) Both lights will be on d) Both lights will be off 78. Given this circuit: A A switch is added at point A. If the switch is open, what will happen? a) L1 will be on and L2 will be off b) L1 will be off and L2 will be on c) Both lights will be on d) Both lights will be off

34 79. Which of the following correctly shows the magnetic field lines of a bar magnet? a) b) S S c) d) S S 80. Which one of the compasses below is correctly indicating the magnetic north? D a) b) S S c) d) S S 81. If a compass were placed at the following position, in which direction would it point? D S Compass placed here a) b) c) d)

35 82. If a compass were placed at the following position, in which direction would it point?b Opposites attract S Compass placed here a) b) c) d) 83. Current flowing through a live wire creates a magnetic field. If a compass is placed right on top of the wire in position indicated below, in which direction would the compass point? B (use left hand rule; let your thumb from left hand point left where the compass is because the electrons are coming from the negative (short bar) a) b) c) d)

36 84. Current flowing through a live wire creates a magnetic field. If a compass is placed right on top of the wire in position indicated below, in which direction would the compass point? B a) b) c) d) 85. Given the current carrying wire below, and the compass which is placed directly on top of the wire, + Compass placed here in which direction will the compass point? D a) b)

37 c) d) 86. Given the current carrying wire below, and the compass which is placed directly on top of the wire, + Compass placed here in which direction will the compass point? C a) b) c) d) 87. A vertical circuit is set up, and a piece of cardboard is placed perpendicular (90 ) to the wire A D B C In which direction will the compass at B point? D a) b)

38 c) d) 88. A vertical circuit is set up, and a piece of cardboard is placed perpendicular (90 ) to the wire A D B C In which direction will the compass at C point?a a) b) c) d)

39 89. A vertical circuit is set up, and a piece of cardboard is placed perpendicular (90 ) to the wire A D B C In which direction will the compass at D point?b a) b) c) d) 90. Marc opens 4 lamps in his house and keeps them all on for 3 hours. The power rating is written on each lamp: Lamp A: 500 W Lamp B: 2 kw Lamp C: 200 W Lamp D: 4 kw Which lamp would cost him the most amount of money for the three hour period? a) Lamp A b) Lamp B c) Lamp C d) Lamp D

40 91. Given this circuit: A A switch is added at point A. If the switch is open, what would happen? a) L1 will be on and L2 will be off. b) L1 will be off and L2 will be on. c) Both L1 and L2 will be off. d) Both L1 and L2 will be on. 92. Which of the following wires would provide the best conductance? a) Length: 2m ; thickness 10 mm ; material: copper b) Length 3 m; thickness 5 mm ; material: copper c) Length 3 m; thickness 15 mm ; material: nichrome d) Length 3 m; thickness 10 mm; material: nickel

41 93. What is the difference between the three methods in charging an object: friction, conduction and induction? Method Before During After Friction Two neutral objects Electrons will transfer from one to the other One will be (+); other (-) Conduction (touching) Induction (not touching) Once charged, one neutral + + Once charged, one neutral + Electrons will flow from neutral to positive charge The negatives will move to the left side of the neutral sphere because they are attracted to the positive sphere. If there s enough positive charge in the one on the left, there will not be enough electrons to neutralize it, and both will be positive. They will go back to theoriginal.

42 94. In the laboratory, a student was given an acetate ruler, a cotton cloth and the following electrostatic series. Capacity to Rubber gain electrons Cotton Silk Wool Acetate The diagram below shows the distribution of the charges in each substance Acetate Ruler Cotton Cloth The student rubbed the acetate ruler with the cotton cloth. a) Taking into account the initial diagram, draw the charges in the acetate ruler and in the cotton cloth after they were rubbed together. Will lose electrons Acetate Ruler will gain electrons Cotton cloth b) State the charge on the acetate ruler and the charge on the cotton cloth after they were rubbed together. Justify your answer. Acetate = (+) Cotton cloth = (-)

43 95. You rub a balloon on your hair in order to stick the balloon on the wall. Which of the following statements is TRUE? A) When rubbed together, both the balloon and your hair become positively charged. B) When rubbed together, both the balloon and your hair become negatively charged. C) When rubbed together, the balloon remains neutral and your hair becomes negatively charged. D) When rubbed together, the balloon becomes negatively charged and your hair becomes positively charged. 96. Silk and glass are two electrically neutral materials. Silk can be represented by and glass by. After these materials are rubbed together, silk becomes negatively charged and glass becomes positively charged. Which of the following models may represent silk and glass after these materials have been rubbed together? A) silk glass B) silk glass C) silk glass D) silk + glass

44 97. We are given four spheres, A, B C and D. Sphere A is positively charged and the charges on spheres B, C and D are unknown. The following diagram shows what happens to these spheres if we suspend them two by two close to each other. A B B C C D Given the diagram above, what are the charges on spheres C and D? A) Sphere C is positively charged and sphere D is negatively charged. B) Sphere C is positively charged and sphere D is positively charged. C) Sphere C is negatively charged and sphere D is negatively charged. D) Sphere C is negatively charged and sphere D is positively charged.

45 98. Four charged spheres A, B, C and D are suspended from wires. The following diagrams show what happens when these spheres are suspended in pairs close to each other. A B A C B D Spheres A and D are suspended close to each other, as are spheres B and C. Which of the following pairs of diagrams correctly shows what will happen to these spheres? A) A D B C B) A D B C C) A D B C D) A D B C

46 99. You are asked to confirm the following hypothesis: Hypothesis: IF a plastic ruler is rubber with a wool cloth, THE the ruler becomes negatively charged. You know the following as a fact: When you rub a balloon on your hair, the balloon becomes negatively charged. You have the following materials: - 1 plastic ruler - 1 balloon - your hair - 1 piece of wool Explain the produce you would use to do this. In your explanation, list the steps involved in this procedure and describe the way the charged objects will behave after all these steps have been performed. STEPS IVOLVED: 1. Rub ruler with wool cloth. 2. Rub balloon with hair. 3. Move ruler towards balloon. 4. Move wool towards hair. THE WAY THE CHARGED OBJECTS WILL BEHAVE: If hypothesis is correct, then the hair-rubbed balloon(-) will be repelled by the ruler(-) The hair(+) will also be repelled by the wool. But the wool should attract the ruler, if the hypothesis is correct.

47 100. Consider the following experimental results: A. Two glass rods rubbed on silk repel each other. B. An ebonite rod rubbed on fur attracts a glass rod rubbed on silk. C. A piece of sulphur rubbed on flannel repels an ebonite rod rubbed on fur. a) What can you conclude from statement A about the charges on the glass rods? They have the same charge. b) What can you conclude from statement B about the charges on the ebonite rod and the glass rod? They have opposite charges. c) What will happen if the glass rod in statement A is placed near the piece of sulphur in statement C? Explain your answer. They will attract. The sulphur repelled ebonite, implying that the ebonite and glass have the same charge. 2 Possibilities, but same result: glass(+), ebonite (-), sulphur(-), so glass and sulphur attract Or glass(-), ebonite (+), sulphur(+), so glass and sulphur still attract

48 101. Draw lines to connect the elements in the three columns. Definition a) current intensity 2A b) electrical power 3B 1. the amount of energy transferred between two points in an electrical circuit 2. the number of electrical charges that flow past a given point in a circuit within a given time Unit of measurement A. ampere B. watt c) potential difference 1C 3. the amount of energy released per unit of time C. volt 102. Mr. Lane uses an electric mower to cut his grass. The house is 10 m from the street, and the back yard is 30 m long. This summer, you are cutting Mr. Lane s grass for him. He explains that, to do the front lawn, he plugs a 15-m extension cord into an outlet on the outside of the house. For the back yard, he needs a 30-m extension cord, also plugged into an outside outlet. He tells you that his mower cuts the front lawn better than the grass at the back, but he does not understand why. a) How would you explain the difference in the mower s efficiency? The longer wire increases resistance, lowers current and reduces power.

49 b) You talk to your father about Mr. Lane s problem. He tells you that the next time you cut the grass he will lend you a 30-m extension cord to do the lawn behind the house. You notice that, with this extension cord, there is no longer any difference between the mower s efficiency on the front and back lawns. How do you explain this improvement? This enforces the idea that the length of the cord was the cause A soft iron rod is magnetized with a bar magnet, as shown in the diagram below. Identify the poles of the iron rod. S 104. Draw the position of the needle in each of the compasses placed near the magnets or wire illustrated below. a) b) S S Compass I Compass II c) + Compass III placed beneath the wire 105. Draw a magnetic field for each of the following examples a) S S

50 b) S S c) S

51 106. An electric current flows through a straight wire and produces a magnetic field. Which of the following diagrams correctly represents this magnetic field? A) B) C) D) How must the ammeter and the voltmeter be connected? A) C) V Appliance A Appliance V A

52 B) Appliance A D) V Appliance V A 108. What are the requirements necessary for one object to be able to magnetize another object? One of the objects has to be a permanent magnet while the other one has to be ferromagnetic What happens to the domains when an object gets magnetized? Their magnetic fields align and as they cooperate they act as much bigger and stronger magnetic field Give two properties of magnetic field lines for magnetism. They never cross each other. The more densely packed they are, the stronger the field is. A compass will align itself with the lines, revealing that the north end of the compass is always seeking south.