Measurement in Science

Systems of Measurement In the United States, we normally use the United States Customary System (USCS), which is also known as the British system. In the United States, we normally use the United States Customary System (USCS), which is also known as the British system. We also use Système International (SI) d’ unitès, which is also called the metric system. We also use Système International (SI) d’ unitès, which is also called the metric system. For example, if you went to the store and were going to buy a bottle of Pepsi for your family, what size bottle would you buy? Is that USCS or SI? For example, if you went to the store and were going to buy a bottle of Pepsi for your family, what size bottle would you buy? Is that USCS or SI? If you went to the store to buy some milk for your family, what size bottle would you buy? Is that USCS or SI? If you went to the store to buy some milk for your family, what size bottle would you buy? Is that USCS or SI?

Measurement in Science In Science we normally use the SI system. In Science we normally use the SI system. This allows scientists all over the world to understand the measurements that other scientists make when conducting an experiment. This allows scientists all over the world to understand the measurements that other scientists make when conducting an experiment. It also sets a very specific standard for measurement that is used in international commerce. It also sets a very specific standard for measurement that is used in international commerce. Ever make a $328 million measurement error? NASA did with the Mars Climate Orbiter. Ever make a $328 million measurement error? NASA did with the Mars Climate Orbiter.Mars Climate OrbiterMars Climate Orbiter

Measurement Basics Every measurement consists of a value and a unit, which is normally represented by a symbol. Every measurement consists of a value and a unit, which is normally represented by a symbol. For example, if I asked you what your weight was, you could say 100. Does that mean 100 pounds or 100 Newtons? Is there a difference? Yes! 100 Newtons is equal to 220 pounds. For example, if I asked you what your weight was, you could say 100. Does that mean 100 pounds or 100 Newtons? Is there a difference? Yes! 100 Newtons is equal to 220 pounds. Therefore it is essential that you include units in ALL of your measurements. Therefore it is essential that you include units in ALL of your measurements.

SI Units Physical Quantity (dimension)Unit NameAbbreviation Physical Quantity (dimension)Unit NameAbbreviation Masskilogramkg Masskilogramkg Lengthmeterm Lengthmeterm Timeseconds Timeseconds Temperature (official)kelvinK Temperature (official)kelvinK Temperature(common)Centigrade°C Temperature(common)Centigrade°C VolumeLiterL VolumeLiterL Amount of Substancemolemol Amount of Substancemolemol Electric CurrentAmpereA Electric CurrentAmpereA Electrical VoltageVoltV Electrical VoltageVoltV

SI prefixes teraTtrillion1,000,000,000,000 1 X X gigaGbillion1, 000, 000, 0001 x 10 9 megaMmillion1, 000, 0001 x 10 6 kilokthousand1, 0001 x 10 3 hectohhundred1001 x 10 2 dekadaten101 x 10 1 STANDARDone11 x 10 0 UNIT (SU) decidtenth0.11 x centichundredth0.011 x millimthousandth x micro µ millionth x nanonbillionth x Prefix Symbol Amount Number Scientific Notation

prefix usage prefix usage Prefixes are added to SI units so that the measurement is not unreasonably large or small. Prefixes are added to SI units so that the measurement is not unreasonably large or small. For example, if you wanted to know the distance from Waterford to New York City What unit would you use? For example, if you wanted to know the distance from Waterford to New York City What unit would you use? km = kilometers = 1000 meters km = kilometers = 1000 meters Using just meters would end up with a very large number. Using just meters would end up with a very large number. What if you wanted to measure your foot? What unit would you use? What if you wanted to measure your foot? What unit would you use? cm = centimeter = 1/100 meters or.01 meters cm = centimeter = 1/100 meters or.01 meters

Making Precise measurements - What would you say is the measurement at the arrow in this centimeter ruler? 2.2 cm is the correct measurement. It is 2.2 because it is a little more than 2.0, but less than 2.5 Please note that in this measurement, you ESTIMATED a digit based on the tool that you were using to measure.

Measurement Precision -What would be your measurements at arrow A and B on this centimeter ruler? A B A = 4.8 cm B = 8.0 cm Why is B 8.0 cm? Because you estimated a digit! It is important to report the best precision that your measuring device allows!

Measurement Precision -What would be your measurements at arrow A and B on this centimeter ruler? A B A = 1.25 cm B = 2.20 cm C = 3.00 cm Remember to estimate a digit to report the appropriate precision! C

Confused about estimating a digit- use this trick! If you are unsure about how many digits you should report in a measurement, just pick a spot on your measuring tool that is not on any one of the lines. Make your measurement and look at how many digits you have. Then, when you use that tool later, use the same amount of digits each time! If you are unsure about how many digits you should report in a measurement, just pick a spot on your measuring tool that is not on any one of the lines. Make your measurement and look at how many digits you have. Then, when you use that tool later, use the same amount of digits each time!

Using the trick A A = 1.25 cm C = 3.00 cm C Lets say you want to get the measurement at location C. You are unsure how many digits to use. Just make the measurement at A and you will easily see that you will need 2 digits after the decimal point. That tells you that you need 2 digits after the decimal point for your measurement at point C!

Making unit conversions Converting from one unit to another in science is an important skill. Converting from one unit to another in science is an important skill. One method that includes values from 1000 to 1/1000 involves just moving the decimal point and using a simple pneumonic. One method that includes values from 1000 to 1/1000 involves just moving the decimal point and using a simple pneumonic. For example, what if I asked you how many mm were in cm? For example, what if I asked you how many mm were in cm?

Conversions First, you use the following pneumonic to remember the first letter of the prefixes: First, you use the following pneumonic to remember the first letter of the prefixes: Kangaroos Have Dirty Underwear Don’t Check Mine Kangaroos Have Dirty Underwear Don’t Check Mine kilo- hecto- decka- unit deci- centi- milli- kilo- hecto- decka- unit deci- centi- milli- k h da u d c m k h da u d c m Next, figure out what unit you have and what unit you want. Note the number of places you have to move over and which direction. Then, move the decimal that number of times in that direction. Next, figure out what unit you have and what unit you want. Note the number of places you have to move over and which direction. Then, move the decimal that number of times in that direction.

How many mm are in cm? kilo- hecto- decka- unit deci- centi- milli- kilo- hecto- decka- unit deci- centi- milli- k h da u d c m k h da u d c m You have to move one to the right to go from centi- to milli-. You have to move one to the right to go from centi- to milli-. So move the decimal point one to the right. So move the decimal point one to the right. So, mm = cm So, mm = cm What if I asked you how many meters were in 5.34 kilometers? What if I asked you how many meters were in 5.34 kilometers? 5.34 kilometers = 5340 meters (move the decimal 3 places to the right) 5.34 kilometers = 5340 meters (move the decimal 3 places to the right)

Using conversion factors Another way of converting units is using conversion factors. Another way of converting units is using conversion factors. You do this all the time. For example if I asked you how many eggs are in 2 dozen, what would you say? You do this all the time. For example if I asked you how many eggs are in 2 dozen, what would you say? There are 24 eggs in 2 dozen. You used the following conversion factor to determine this: There are 24 eggs in 2 dozen. You used the following conversion factor to determine this: 2 dozen X 12 eggs = 24 eggs 2 dozen X 12 eggs = 24 eggs 1 dozen 1 dozen

Conversion factors See, Conversion factors are easy! See, Conversion factors are easy! Here is what you generally need to do: Here is what you generally need to do: what you have X What you want = What you have what you have X What you want = What you have Then just do the math and you are all set! Then just do the math and you are all set! Try to figure out how many minutes are in 24 hours. Try to figure out how many minutes are in 24 hours.

How many minutes are in 24 hours what you have X What you want = What you have what you have X What you want = What you have 24 hours X 60 minutes = 1440 minutes 24 hours X 60 minutes = 1440 minutes 1 hour 1 hour So you just have to multiply 24 by 60, cancel the hours and you are done! How many seconds are in 1 year?

Precision vs. Accuracy Example: A 100 meter dash is timed by 4 different judges. Here are the results: Example: A 100 meter dash is timed by 4 different judges. Here are the results: Judge s Judge s Judge 29.6 s Judge 29.6 s Judge s Judge s Judge 410 s Judge 410 s Which is the most precise? Which is the most precise? Judge 1 Judge 1 Which is the least accurate? Which is the least accurate? Judge 3 Judge 3

Precision vs. Accuracy Judge s Judge s Judge 29.6 s Judge 29.6 s Judge s Judge s Judge 410 s Judge 410 s Accuracy is how close the measurement is to the actual value. Because Judge 3 had a time that was significantly different than the others, we can assume that her time was inaccurate. Accuracy is how close the measurement is to the actual value. Because Judge 3 had a time that was significantly different than the others, we can assume that her time was inaccurate. Precision is a gauge of how exact a measurement is. Therefore, the most precise measurement was taken by Judge 1. Anyone know a person who can run that time in 100 meters? Precision is a gauge of how exact a measurement is. Therefore, the most precise measurement was taken by Judge 1. Anyone know a person who can run that time in 100 meters?