Unit 1: Science Skills, Measurement, and Conversions

Transcription

1 Chemistry Practice test Period: Name: Skare Fall 206 Date: pae of 5 Unit : Science Skills, Measurement, and Conversions Learnin Tarets & Sample Questions Most of what we ve done is in Ch. 3 of your book. 3. scientific notation, sinificant fiures 3.2 SI units, metric prefixes and meanins, density 3.3 conversion factors, dimensional analysis, usin density as a conversion factor Measurement, Units, Problem Solvin and Calculations. Apply sinificant fiures rules in all calculations. 2. Understand the rules for estimation. a. Be able to estimate to the correct diit iven a measurin device. b. Given any measurement, determine which diits were estimated, which were certain, and what the smallest division on the measurin device was. 3. Understand scientific notation (and how to enter it in a calculator) and use in calculations/answers whenever convenient/necessary for sinificant fiures. 4. Know the metric units for lenth, mass, temperature, and time. 5. Know the metric units of common quantities used in chemistry, and their relative sizes: a. rams = mass; liters = volume; meters = lenth; seconds = time; also, that cm 3 = ml 6. Be able to convert within the metric system usin units for lenth, mass, volume and combinations of units. a. Understand the metric system units and multipliers (prefixes) for measurin lenth, volume, and mass.; o back and forth specifically between kilo, base, centi, and milli prefixes for any metric base. e..: k = 000 ; = 00 c; = 000 m. b. Know the meanin (multiples of powers of ten) of the metric prefixes: kilo = 000 or 0 3 ; centi- = /00=0.0 =0-2 ; milli- = /000= 0.00 = Be able to use units and unit analysis (dimensional analysis) to solve problems a. Write conversion factors usin equivalent quantities and units. b. Set up multiplication steps to cancel (like factors) units showin units! 8. Understand density in terms of units and the conceptual meanin and relationship between terms. a. Given an increase or decrease in one term while keepin another term constant, conceptually, how must the 3 rd term chane and why. b. Be able to use units to calculate a missin term, iven the other two values. 9. Know the three main temperature scales and how to convert between them. a. Know the meltin and freezin and boilin points of water (at sea-level and standard atmospheric conditions) in the three temperature scales. b. Given a numeric temperature and a certain condition, be able to determine what temperature scale(s) could the value be measured in.

2 Chemistry Practice test pae 2 of 5 As always: ) SHOW ALL WORK, with UNITS IN WORK, 2) use appropriate sinificant fiures on you final answer (keep all values in your calculator and just round the final answer), 3) when writin out scientific notation iven by a calculator write out what it actually means NOT the E. On the test, if it s not clear you understand where the final answer/units come from, your Practice Test. A person records the lenth of a pencil in the scientifically accepted manner as 0.2 cm. a) Which diit(s) is/are estimated? The 2 (/0s spot) How do you know? When measured in the accepted manner the last sinificant diit shown in the estimated diit. b) Which diit(s) is/are certain? The & 0 (0 s and s spot) How do you know? Since only the last sinificant diit is estimated, the others must be certain. c) The smallest division shown on the measurin device is: cm How do you know? We can reliably estimate to /0 th of the smallest division shown on the device. Since we estimated to the nearest 0.cm space, that means the smallest unit must be cm (/0 th of cm = 0.cm) 2. How many sinificant fiures are in these measurement numbers: a) (leadin 0 s don t count, but trailin 0s do with dec. point shown) b).75 x (only coeff [or sometimes called the base] on sci. notation count) c) 692,000 3 (no dec. pt, so trailin 0 s don t count) 3. Round the followin to the listed number of sinificant fiures: a) to 3 si. fi (leadin 0 s aren t sinificant., and the 7 makes the 2 nd 3 round up) b) 23,456 to 3 si. fi. 23,500 (4 round up to 5, need trailin 0 s that aren t sinificant = no decimal pt) d) (captive 0 s count) e) 56,000 2 (no dec. pt, so trailin 0 s don t count) f) x (only coeff [sometimes called base] on sci. notation count, and with dec. pt. the trailin 0 counts) c) 5,449 to 2 si. fi. 5,400 ( st 4 rounds downs, need trailin 0 s that aren t sinificant = no decimal pt) d) 2,973.5 to 2 si. fi. 3.0x0 3 (rounds to 3,000, s.f. w/o dec pt., 4 s.f. w/ dec pt. so need sci. notation) 4. Consider the addition of 250. to 5.7. What is the mathematical answer? If these were lenth measurements (250. cm cm) what answer would you report, and why? 266cm because 250. has 0 diits after the decimal point, where as 5.7 has 2 diits after the decimal point. When addin or subtraction we have to use the same number of diits after the decimal as the number with the fewest decimal places, so we must have 0 decimal points 5. Consider multiplyin 6.2 x What s the mathematical answer? If these were measurements, (6.2 ml x 6.46 /ml) what answer would you report, and why?.0x0 2 because 6.2 only has 2 si fis, while 6.46 has 4, but in multiplication and division our answer must have the same number of si. fis. as the term with the fewest number of si. fis., so 2 si. fis rounded after the 2 nd si fi rounds to 00, but 00 only has si. fi, and 00. Has 3 si fis, so we need to express in sci. notation to et the 2 si fis. It s because ml/ml, ml cancel, leavin only. 6. Write 230,000 in scientific notation, indicatin 3 sinificant fiures. 2.30x0 5 (we must multiply 2.30 by 0 a total of 5 times to equal 230,000) 7. Write the measurement 00 cm with 2 sinificant fiures..0x0 2 cm (need sci. notation) 8. List the SI unit name and abbreviation for: lenth meter (m) ; time second (s) List the unit name(s) and abbreviation(s) for the metric (not SI standard) units we use for: mass ram (); volume milliliter or cubic centimeters (ml or cm 3 ); density rams per milliliter (/ml) or rams per cubic centimeter (/cm 3 ) 9. What metric unit and appropriate prefix, if any, would be most appropriate to describe: a) a allon of asoline liter (no prefix) allon is about liters b) thickness of a human hair millimeter (mm) or micrometers (µm) hair is about 0.06mm or 60 µm c) a pound of hamburer kiloram (k) or hectoram (h) on Earth lb is k = h 0. Usin different unit prefixes, write in 3 different ways :,000 ml L kl,000 L = 500 ml; = kl 00 cl L = 50 cl; 0 dl L d) mass of a human hair millirams (m) or microrams (µ) a human hair is about 0.6 m = 600 µ e) volume of a drop of water milliliter (ml) or microliters (µl) drop of water = 0.05 ml = 50 µl) f) lenth of one side of a house meters (m) or dekameters (dam) side 5 m =.5 dam = 5 dl; dal = 0.05 dal; hl = hl; 0 L 00 L

3 Chemistry Practice test pae 3 of 5. Usin conversion factors (showin process in each case), determine a) what 20 cm is in meters : c) what 5.4 liters is in cl: 20 cm m =.2 m 5.4 L 00 cl = 540 cl 00 cl L b) what 0.54 km is in mm: d) what 20m is in k 0.54 km,000 m km,000 mm m = 540,000 mm 20 m k,000 m, Which is larer, 50 mm or.3 cm? Explain how you determined the answer. Since there are 0mm for every cm, 50mm cm 0mm 3. What is the metric prefix to indicate the followin: = k = 5cm, so 50mm = 5cm is larer than.3 cm a) /000 of a unit? milli- b) 000 of a unit? kilo- c) /00 of a unit? centi- 4. Convert 0.3 cm to ft. ( in = 2.54 cm, 2 in = ft ) 0.3 cm in 2.54 cm ft = ft = ft (3 si. fi., both conversion factors are exact) 2 in 5. Convert 9.83 k to pounds. ( pound = ) 9.83 k 000 k 6. Convert.83 m to inches. ( in = 2.54 cm) lb = lb = 2.7 lb (3 si. fi., the k conversion is exact) m 00 cm m in = in = 72.0 in (3 si. fi., both converions factors are exact) 2.54 cm 7. Calculate the density in /ml or /cm 3 for an object with a mass of 234 and a volume of 2.2 cm 3. We have, and we have cm 3, so we just need to divide them to et /cm 3 : 0 cm 3 (2 si. fi. ) cm 3 = cm 3 = 8. Calculate the density in /ml or /cm 3 for an object with a mass of.2 lbs. and volume of 2.2 ft 3. ( k = lbs; in = 2.54cm) ft 3 = ftftft, ft 3 = 2in2in2in =,728in 3, and in 3 = ininin = 2.54cm2.54cm2.54cm = cm 3.2 lbs 2.2 ft 3 ft 3,728in 3 in cm 3 k 000 = lbs k cm 3 = (2 si. fi. ) cm3 9. Calculate the volume in ml if the density of an object is 0.88 /ml and you have 50. rams of the substance. Show work as a unit conversion. 50 ml = ml = 57 ml (2 si fi) 0.88

4 Chemistry Practice test pae 4 of Convert each of the followin temperatures to the equivalent temperatures in the other two scales. Make sure to show your work with units! Fahrenheit Celsius Kelvin 78 ºC -40ºF Fill out the followin table with the appropriate temperatures in Celsius, Kelvin, and Fahrenheit. For freezin and boilin points, assume at sea-level under standard atmospheric conditions. Temperature point Fahrenheit Celsius Kelvin Absolute zero Freezin point of water Boilin point of water Standard Human Body Temperature Standard room temperature

5 Chemistry Practice test pae 5 of For each of the followin temperatures and descriptions, determine which of the three common temperature scales (Celsius, Kelvin, and/or Fahrenheit) could be true (note you aren t limited to just the Earth when considerin your answers) and explain why. If any temperature scales could be excluded, make sure to explain why you can exclude the scale(s) you didn t include. a) The low temperature of the day somewhere on Earth is -0: b) Water cooled to a temperature of 20 would freeze c) Within a matter of a few minutes or less, exposin a person to a temperature of 90 would prove fatal: d) A temperature of 400 would mean any water would be steam e) Water is cold, but not frozen at a temperature of 5 f) Water is a still frozen at a temperature of 250 ) Water is cold, bu not frozen at a tempeature of 40