2004-2005 P.O.D.s Q. Izzy earns 16 out of 20 possible points on a science quiz. What is her grade, expressed as both a percentage and a letter grade? A. 16/20 x 100 = 80% or C+ ==Science Process Skills== Q. Nia notices Mr. Sanford's right eye is red and asks, "Do you have allergies?" Identify Nia's observation(s) and inference(s). A. Observation: Right eye red. Inference: Redness caused by allergies. Is this a fact? No. The redness could be caused by rubbing my eye, or grapefruit juice in my eye. Note that other causes of red-eye (e.g., lack-o sleep) usually affect BOTH eyes! [Provisioning: Wear an item of college/university-related merchandise.] Q. Where did Mr. Sanford graduate from college? A. Lead post-POD discussion re: observation & inference. Observation(s): Mr. Sanford is wearing a/an [x item] from [x name] college/university (c/u). Inference(s): Mr. Sanford graduated from [x name] college/university. Note: It is certainly possible Mr. Sanford attended [x name] c/u w/o graduating, or visited [x name] c/u, or simply purchased an item of merchandise w/o ever visiting &/or attending the c/u. -- [Bi-POD] Q. 1 L = ? ml A. 1,000 ml Q. 35.6 ml of H2O = ? kg A. 35.6 ml of HOH = 35.6 g of HOH, or .0356 kg -- [Bi-POD] Q. Mr. Sanford got a hair cut. True or False. A. False, he got ALL of his hairs cut! Q. 250 ml of H2O = ? kg A. 250 g of H2O = .250 kg -- Q. A construction contractor ordered a wooden beam 10 m long from a building supply store. The building supplier delivered a beam 20 m long; subsequently, the contractor returned the beam to the supplier. Why? A. It's 2 dam long! -- [Use near date of SEP Equinox.] Q. Show Earthdial image from SEP Equinox and say something like (while pointing), "On the day of the SEP Equinox, the subsolar point crossed the Equator; from that day forward, the subsolar point is moving toward the Tropic of Capricorn." What's wrong with this picture? A. Students may point out the difference between Solar Time and Standard Time (due to Daylight Saving Time), but the point of the question is to realize that the Tropics of Cancer & Capricorn are reversed on the sundial face compared to a globe of the Earth. ==GSLG== Chemi-PODs [Bi-POD] Q. What is the density of H2O? A. By definition, 1 g/cc. Q. An object sinks in H2O. What can you infer about the density of the object relative to the density of water? A. The object is more dense than water. -- [Honors] Q. A graph of mass versus density results in a straight-line graph. What does this mean? (Need a better wording of question.) A. The relationship between mass & volume is constant, that is, density IS a characteristic property! -- Q. The following objects are immersed in water. What should you observe? A) Lead B) Balsa wood C) Ice A. Lead sinks, ice floats, and balsa floats higher. -- [Honors] Q. If the speed of light is 186,000 mi/sec, then how far will light travel in one year (mi/yr)? [re: dimensional analysis] A. 186,000 mi/sec x 60 sec/min x 60 min/hr x 24 hr/day x 365 days/yr = ~6 trillion mi/yr -- Q. Water spills out of a graduated cylinder when measuring the volume of an unknown sample. How will this affect both your measurement of volume and calculation of density? A. The measured volume would be lower; the calculated density would be higher. -- Q. A cube 30 mm on a side has a mass of 100g. What is its density? A. Volume = 27cc; D = 100g / 27cc = 3.704 g/cc -- 19 OCT 2004 Q. When a solute dissolves in a solvent, does a chemical- or physical change occur? A. A physical change. -- 28 OCT 2004 Q. In the following solutions, identify the solute and solvent: - Solution of 400g CuSO4 and 1000 ml of H2O A. CuSO4 = solute; H2o = solvent. - 1:3 solution of ammonia and water A. Ammonia = solute; water = solvent. Q. Refer to the graph on p. 23, Green Lab Manual. 40g of KNO3 is added to 100ml of H2O at 60dC -- is the resulting solution saturated or unsaturated? A. Unsaturated. At 60dC, it takes ~81g of KNO3 to saturate 100ml of H2O. -- 04 NOV 2004 Q. Chef Sanford heats a pot of water to cook pasta. After several minutes, bubbles begin to form in the pot of water. Is this evidence of a chemical or physical change? A. Physical change. When water boils, it simply changes from one phase (or state of matter) to another. -- 10 NOV 2004 H-I-J-K-L-M-N-O Q. What is the preceding substance? A. H-to-O -- 11 NOV 2004 Q. Any of two or more kinds of atoms of the same element having the Atomic No. but differing Atomic Masses is called... a) Isotoner b) Isoconfused! c) Imadope d) Isotope A. Isotope -- 15 DEC 2004 Q. Draw a lemon wet cell battery. Label the parts of the battery. A. Container (lemon peel); electrolyte (lemon juice, acetic acid); electrodes (different substances). -- 16 DEC 2004 Q. You are designing an electric battery. Why is it important to use electrodes made of different substances (elements or compounds)? A. ? ==YSLG== Hot-PODs (heat & temp) 05 JAN 2005 Compare/contrast two samples of water: (A) A cup of boiling water; (B) A lake at 20dC. Q. Which sample has the higher _temperature_? A. Cup of boiling water Q. Which sample contains more _heat_? A. Lake at 20dC -- 06 JAN 2005 Q. A red-hot steel ingot is immersed in a bucket of "cold" water. In terms of both _thermal energy_ (heat) and _temperature_, discuss the results. A. The ingot is the heat source; the water is the heat sink. The temperature of the ingot decreases; the temp. of the water rises (until the two reach equilibrium). -- 07 JAN 05 Q. O.K., I admit it - I lied! [Wait for explanation...] When two substances reach thermal equilibrium, kinetic energy is still transferred between their molecules. Explain how it is possible for their temperatures to remain the same. A. Dynamic equilibrium. -- 10 JAN 2005 Q. What is meant by the term (phrase?) "Dynamic Equilibrium?" See if you can think of an example (non-heat-related)? A. Perpetual change: in balance. Living from paycheck to paycheck. Bucket with a hole in it. -- 13 JAN 2005 Try-POD Q. Two water samples are mixed; what is the temperature after mixing? Sample A = 100 ml @ 60dC; Sample B = 100 ml at 10dC A. 6000C + 1000C / 200 = 35C [Show graph on cover of YLM] Q. When was the rate of heat transfer greatest? A. During the first few minutes. Q. What happened at the 10-minute mark? A. Two samples reached thermal equilibrium. -- 14 JAN 2005 Q. Two water samples are mixed; what is the temperature of the mixture? Sample A = 100 ml @ 50dC; Sample B = 10 ml @ 10dC A. 5000C + 100C / 110 = 46.4C -- [Note: By order of Linda Chin, FCPS ISD, temp conversion problems from either F-to-C or C-to-F are forbidden! Either C-to-K or K-to-C temp. conv. problems are O.K.] Bi-P.O.D.: Q. 15dF = ?C A. C = (F - 32) x 0.56 or C = (15 - 32) x 0.56 or -17 x .56 = -9.52C Q. Titan's surface temperatures of 290 degrees below zero Fahrenheit = ?K A. C = (-290 - 32) x .56 or -322 x .56 or -180.32C K = C + 273 or -180.32 + 273 = 92.68K -- 25 JAN 2005 Q. Radiation from the Sun heats the Earth; the Earth reradiates energy that heats the atmosphere. Why is the atmosphere heated less when the ground is snow-covered? A. Snow is white; white is more reflective. -- 26 JAN 2005 Q. All objects at a temperature greater than absolute zero emit electromagnetic radiation. Relatively "cool" bodies, like the Earth, radiate [more,less] energy at [shorter, longer] wavelengths. A. less; longer 02 FEB 2005 Video Daily Double! 1) Videodisc Movie #69 - "Hot & Cold Dye" Listen to narration; answer question posed by narrator. 2) Videodisc Movie #68 - "Heat Wave" (infrared radiation, atmospheric shimmering) -- 03 FEB 2005 Video Daily Double! 1) Videodisc Movie #60 - "Thermogram (ph)" thermal photgraph of infrared radiation 2) Videodisc Movie #59 - "Convection" (heat transfer) in a boiling liquid using rice tracers -- 07 FEB 2005 Q. Although the heat output of the hotplate was constant, the "Boiling Temperature of Water" graph shows two plateaus, each one indicating that the water temperature did not change for a period of time. Where did the thermal energy (heat) "go" during the times when the temperature did not change? Remember, the Law of Conservation of Mass & _Energy_ says we must be able to _account_ for _all_ of the energy added to the water! A. When temp increased, thermal energy (heat) was transformed into kinetic energy. During temp plateaus (associated with phase changes), thermal energy was transformed into potential energy. -- 17 FEB 2005 Demo-PODs: Set up a 200-Watt lamp 20 cm from a black- and white flower pot. After x min., temps stabilize at 34C (black) and 30C (white). Q. How is energy being transferred from the lamp to the flower pots? A. Radiation Q. Why haven't the temps changed for over an hour? A. Radiative balance Catch-basin used to demo water in = water out. Q. What is the name for the process demonstrated? A. Dynamic equilibrium ==RSLG== Mo-PODs (motion) 14 MAR 2005 Q. What is shown by a graph of distance vs. time? A. Speed Q. What is shown by a graph of velocity (speed) vs. time? A. Acceleration -- 17 MAR 2005 Q. Look *carefully* at the graph you created yesterday (KoT, Avg Spd vs. Dist) -- does it *really* show acceleration? A. No! Avg Spd vs. Time shows acceleration!!! -- 28 MAR 2005 mo-PODs KoT graph of velocity vs. time, showing three line segments: A; B; C. Q. Which line segment shows negative acceleration? A. "C." v(final) - v(initial) = negative number; neg. no. / pos. no. = neg. answer Q. During line segment "B," the truck's acceleration is __________. (A) positive; (B) zero; (C) changing; (D) negative A. Zero. v(final) - v(initial) = 0; 0 / anything = 0 -- 29 MAR 2005 Q. A racecar (I love palindromes!) drives around a perfectly circular racetrack at a constant speed of 55 mph. Is the racecar accelerating? A. Velocity = speed PLUS direction. Although the speed of the racecar is constant, it's direction is constantly changing, therefore it is accelerating. [Begin Future PODs] Mo-PODs [excerpted from PC folder, Physics - Motion - Good PODs] Q. Can two objects have the same speed but different velocities? A. One object going north the other object going south, for example. Q. Can you accelerate while traveling at constant velocity? A. No. Q. Can you accelerate while traveling at constant speed? A. Yes, change direction. Example | Constant Speed? | Constant velocity? Cruise control on straight highway | yes | yes Speeding car slowing down | no | no, speed changing Going around circular track (cruise control) | yes | no, direction changing Roller coaster up-down, slowing down, speeding up | no | no, direction and speed change [End Future PODs] -- 01 APR 2005 Q. How much work is done when a 500 g mass is dragged 200 cm with a force of 5 N? A. W = F x d; W = 5N x 2m; W = 10N-m or 10J -- 13 APR 2005 Q. You may have noticed the door to the classroom has two handles: one located near the outer edge of the door; and one located near the inner edge of the door (close to the hinges). Which one of the two door handles will require less effort force in order to close the door? Explain your answer. A. The handle near the outer edge; the force-distance tradeoff explains... -- 18 APR 2005 Q. Look at the following picture of an MPV: http://www.wsanford.com/~wsanford/gr8ps/red/mpv/pulleycar-m.jpg List all of the simple machines used as part of the MPV. A. wheel & axle, lever, pulley -- 19 APR 2005 Q. If the diameter of a CD-ROM is 12 cm, then what is its circumference? A. C = pi x D, or 3.14 x 12 cm = 37.68 cm Q. In order to travel 5 m, how many times must the CD rotate? A. 500 cm / 37.68 cm = 13.27x -- 27 APR 2005 Q. Given formula F = m x a, solve for acceleration (a). What is the mathematical relationship between a & F; a & m? A. a = F/m; direct; indirect (inverse). Q. Given formula W = F x d, solve for force (F). If the work done is constant, then what is the mathematical relationship between F & d? A. F = W/d; indirect. ==BSLG== Astro-PODs 12 MAY 2005 Q. What is the difference between rotation and revolution? Give an example (preferably from astronomy) of each type of motion. A. Rotation: an object spins around an imaginary axis, e.g., the Earth's rotation causes day & night. Revolution: an object moves around (orbits) another object, e.g., the Earth goes around the Sun in one year. -- 23 MAY 2005 Q. List the planets in our Solar System in order of distance from the Sun. A. M, V, E, M, J, S, U, N, P -- 26 MAY 2005 Q. If the Moon is in the First Quarter phase, then approximately how many days 'til Last Quarter? A. ~14 days -- 27 MAY 2005 Q. In your measurement of the Sun's diameter, the distance between the "lens" and "film" cards is too large. How would this error affect your experimental value (E.V>)? A. The EV would be too small.