Unit 3 review: Scientific measurement



Unit 3 review: Scientific measurement Name:

Essential question: What should a scientist consider when measuring materials? Period:

|3.1 ( |

|Measurement |Which of the following is a measurement? |

| |700 or 60 grams |

| | |

| |A measurement is a quantity with a number AND a unit. |

|Accuracy vs. Precision |Accuracy: How close a measurement comes to the actual/true/accepted value |

| |Precision: A measure of how close a series of measurements are to each other [you can’t decide if a measurement is precise unless |

| |you have TWO OR MORE repeated measurements] |

|Scientific notation |Scientific notation is ONE WAY to deal with VERY LARGE or VERY SMALL numbers. |

| | |

| |VERY LARGE |

| |VERY SMALL |

| |130,000,000 Liters = 1.3 x 108 Liters |

| |0.0003409 = 3.409x10-4 |

| |3,000,000,000,000 = 3 x 1012 0.000 000 000 000 000 000 000 327 grams= |

| |3.27 x 10-22 grams |

|Accepted(actual) vs. |Accepted/actual value = The CORRECT value based on reliable measurements |

|Experimental (measured) | |

| |Experimental/measured value = A value MEASURED in the lab (Example: You may have an unknown solid in the lab… to guess it’s |

| |density, you would measure the mass, and it’s volume, then calculate density, and compare your EXPERIMENTAL density to a table of |

| |ACCEPTED/ACTUAL density values. |

|Error vs. Percent error |Error = experimental value – accepted value |

| | |

| |Percent error = _____׀error׀_____ x 100% |

| |Accepted value |

|SIGNIFICANT FIGURES |

|Counting sig figs |Every nonzero digit is significant |

| |(24.3 has three sig figs, 714 and .714 both have 3 sig figs) |

| |Zeros BETWEEN nonzero numbers are significant (7003 has 4 sig figs) |

| |Zeros to the left of nonzero digits are NOT significant, they are place holders |

| |(0.007 has one sig fig, 0.000 009 824 has four sig figs) |

| |Zeros at the end of a number to the right of a decimal are significant, they INDICATE SOMETHING HAS BEEN MEASURED TO A CERTAIN |

| |PRECISION |

| |(42.00 has four sig figs, 43.010 has five sig figs) |

| |Zeros to the right of a nonzero number that DON’T pass the decimal are placeholders, and NOT significant |

| |(300 has one sig fig, 27, 210 has four sig figs) |

|Rounding sig figs |If you need to ROUND sig figs, you need to know how many sig figs your answer needs, and look at ONE digit after to see if you |

| |should round… |

| |- Round 45,890 to three sig figs ( 45,900 (you start to the leftmost sig fig, so 4, 5 and 8 will be kept, and 9 determines if 8 |

| |is rounded up… |

| |- If the number after your last sig fig is 0-4, DON’T ROUND |

| |- If the number after your last sig fig is 5-9, ROUND |

|Adding/subtracting sig figs|Look at the numbers your’re adding or subtracting… whichever number has the LEAST digits after a decimal tells you how many decimal|

| |places your answer should have (YOU ARE NOT COUNTING SIG FIGS HERE, YOU ARE COUNTING PLACES AFTER THE DECIMAL!!! |

| | |

| |5.5901 (four numbers AFTER the decimal) |

| |+25.301 (three numbers AFTER the decimal) |

| |30.8911 ( Round to 30.891 |

|Multiplying/dividing sig |Whichever one of your numbers has the LOWEST SIG FIGS, round your answer to that number: |

|figs |6.1001 (five sig figs) |

| |X 2.0___ (two sig figs) |

| |12.2002 ( 12 (answer is rounded to two sig figs) |

|3.2 ( The International System of Units (SI system) | |

|Common units |Meter, kilogram, Kelvin, second, mole, Liter |What are each of these used to measure? |

|SI BASE UNITS |

| |

|Quantity |SI base unit |Symbol |

|Length |Meter |m |

|Mass |kilogram |Kg |

|Temperature |kelvin |K |

|Time |second |s |

|Amount of a substance |mole |mol |

|Luminous intensity |Candela |cd |

|(light) | | |

|Electric current |ampere |A |

| | | |

|METRIC PREFIXES |

|Prefix |Meaning |Factor |

|Mega (M) |1 million times larger than the unit it precedes |106 |

|Kilo (k) |1000 times larger than the unit it precedes |103 |

|Deci (d) |10 times smaller than the unit it precedes |10-1 |

|Centic (c) |100 times smaller than the unit it precedes |10-2 |

|Milli (m) |1000 times than the unit it precedes |10-3 |

|Micro (µ) |1 million times smaller than the unit it precedes |10-6 |

|Nano (n) |1000 million times (1 billion times) smaller than the unit it |10-9 |

| |precedes | |

|Pico (p) |1 trillion times smaller than the unit it precedes |10-12 |

|What is the difference between MASS and WEIGHT? |

|MASS |Measure of how much matter something has |Measured in grams |

|WEIGHT |- Measure of the FORCE of GRAVITY between two objects (like you and |Measured in Newtons, pounds |

| |the Earth) | |

| |- Depends on the MASS of each object, and the DISTANCE between them | |

| |(more mass = more gravity; more distance between two objects = less | |

| |gravity) | |

|3.3 |

|Conversion factors |If you think about any equal measurements ($1 = 2 quarters = 10 dimes = 100 pennies) you can use them to create a conversion |

| |factor: __$1____ or _10 dimes__ 10 dimes |

| |4 quarters 100 pennies $1 |

|Dimensional analysis |Using conversion factors to analyze and solve problems ( essentially this is just changing units! |

|Converting between units |1000 meters = 1 km |

| | |

| |How many meters are in 4.3 km? ( 4.3 km__׀__1000 m = 4,300 m |

| |׀ 1 km |

|Single step |If you are converting from a base unit to a unit with a prefix, or the reverse, you only need one step: milliliters to liters, |

| |grams to kilograms, seconds to microseconds… |

| | |

| |5.8 kg 1000 grams = 5800 grams 1200 milliliters ׀ 1 liter = 1.2 Liters |

| |1 kg 1000 milliliters |

|Two step |If you are converting between two base units with prefixes… it is easiest to convert to the base unit, and then to your answer. |

| | |

| |Convert 5.8 kg to mg Convert 1200 ml to dl |

| |Starting value Convert to g Convert to mg Starting value |

| |convert to L convert to dL |

| | |

| |5.8 kg 1000 g 1000 mg = 5800 grams 1200 ml 1 L 10 dL |

| |= 1.2 Liters |

| |1 kg 1 g 1000 ml 1 L |

|Complex |If you need to convert multiple units in one expression, simply follow your steps for one or two step conversion, just pay |

| |attention to your units and make sure you use the correct conversion factors! |

| | |

| |Example: Convert 12 kg/L to g/mL |

| | |

| |Starting value Convert to grams Convert to mL |

| |12 kg 1000 g 1 L =12 g/mL |

| |L 1 kg 1000mL |

|3.4 |

|What determines density? |Density is a ratio of mass to volume |

|How does temperature change|In general, increasing temperature DECREASES density |

|affect density? | |

|How do we calculate |Density is calculated as mass/volume= Density |

|density? |You MUST make sure your units of mass and volume are represented in your new unit for density: |

| | |

| |Example: Density of water ( 1 gram of water/1 mL of water = 1 g/mL water |

|How can we incorporate |If you have two out of three of the following: mass, volume, density… then you can calculate the third: |

|density into dimensional | |

|analysis? |1) Density = mass/volume 2) Volume = mass/density 3) Mass = Density x volume |

Name: Period:

|TESTING YOUR SKILLS (3.1): Use your notes and your Unit 3 study guide to answer the questions below, to see if there are any sections that you’re still not |

|clear on… |

|Can I determine accuracy vs. precision? |Three students took measurements in a lab of a sample which had an actual mass of 47.2 grams… were the following |

| |students’ measurements accurate? Precise? |

| | |

| | |

| |James |

| |Jasmine |

| |Javon |

| | |

| |Measurement 1 |

| |45.1 g |

| |47.1 g |

| |49.2 g |

| | |

| |Measurement 2 |

| |45.0 g |

| |47.3 g |

| |43.1 g |

| | |

| |Measurement 3 |

| |45.1 g |

| |47.2 g |

| |40.9 g |

| | |

| |Accuracy? (High/low) |

| | |

| | |

| | |

| | |

| |Precision?(high/low) |

| | |

| | |

| | |

| | |

|Can I convert back and forth between |Convert the following decimals and scientific notations |

|decimals and scientific notation WITHOUT | |

|a calculator? |0.0004 |

| |4 x 10-4 |

| | |

| | |

| |7.89 x 107 |

| | |

| |46,340,000 |

| | |

| | |

| | |

| |5.2 x 10-9 |

| | |

|Can I calculate error and percent error? |Calculate the ERROR for Measurement 1, for James, Jasmine, and Javon. |

| | |

| |Calculate the % error for Measurement 1 for James, Jasmine, and Javon. |

| | |

|Can I accurately count significant |How many sig figs do the following have? |

|figures? |7007 |

| | |

| | |

| |7.007 |

| | |

| | |

| |7,000,000,000,000,000 |

| | |

| | |

| |8.34 x 10-4 |

| | |

| | |

| |5.000 |

| | |

| | |

| |0.00034 |

| | |

| | |

|Proving your skills (3.2) |

|Can I identify the common SI units AND what they’re used to | |

|measure? | |

|Can I use examples of units and explain gravity to explain | |

|the relationship between mass, weight, and gravity? | |

|Proving your skills (3.3) |

|Can you create a conversion |Create a conversion factor for… |

|factor from equivalent |grams to micrograms cm3 to m3 milligrams to |

|measurements? |micrograms |

|Can you use dimensional analysis |One step: |

|for single step, two step, and |1. Convert 12.5 dL to L |

|complex conversions? | |

| |2. Convert 5,987,620 mg to g |

| | |

| |Two step: |

| |3. Convert 12,560 mL to cL |

| | |

| |4. Convert 45 km to mm |

| | |

| |Complex: |

| |5. Convert 4.5 x 107 km/s to m/s |

|Proving your skills (3.4) |

|Can you identify what things DETERMINE | |

|density? How do you use density in | |

|dimensional analysis? | |

|Can you explain how temperature GENERALLY| |

|affects density (and identify something | |

|that is an exception to that rule)? | |

|Can you explain how to CALCULATE density?| |

|(and use density to calculate mass or | |

|volume? Hint: 3 formulas) | |

|Proving your skills (3.4) |

|Can you use |Calculate density: An object has a mass of 5.6g and a volume of 25mL. |

|the equation |Calculate the object’s density. |

|for density to| |

|calculate |Calculate mass: An object with a volume of 26.7 mL has a density of 0.57 g/mL. |

|density, mass,|Calculate the object’s mass. |

|or volume? | |

| |Calculate volume: An object with a mass of 4.5g has a density of 0.75 g/mL. |

| |Calculate the object’s volume. |

| | |

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