# Scientific Measurements: The Metric System Part I.

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Scientific Measurements: The Metric System Part I

Accuracy vs Precision When you are accurate, you are close to the actual data (you dunk 8 out of 10 baskets) When you are precise, you are “right on the money” (you dunk 10 out of 10 baskets)

The Metric System http://www.youtube.com/watch?v=DQ PQ_q59xyw&safety_mode=true&persis t_safety_mode=1&safe=active

SI Units (Metric System) The International System of Measurement (SI) The metric system (SI) – used so scientists everywhere can communicate with each other. Based on the number 10. Major units: Length = meter volume = liters (liquids) or centimeters (solid or liquid) mass = gram/kilogram (measured by a balance instrument)

Length, Mass, and Volume T he measurement of length is used to find the length, width or height of an object; The measurement of mass is the amount of matter that makes up the object; measured in milligrams, grams or kilograms (paperclip = 1g) Volume is the amount of space the object takes up.

Mass vs Weight Mass is the amount of material that makes up an object. (tent vs house) Weight is completely dependent upon gravity and mass of the object. Since gravity varies in different places, then weight can change, but mass does not! http://www.youtube.com/watch?v=bxZred-4_NU

Length The instrument used for length is the meter stick. If you are dealing with AREA, use the 2 numbers of the area formula (length x width), and square ( 2 ) the answer: 6 m x 4 m = 24 m 2

Volume The instrument for volume can be either the meter stick (for a solid -like a box), or a container (like a bottle or container) for a liquid. Volume, as a solid, can be measured in meters. Volume, as a liquid, can be measured in liters. Volume can also be measured in cubic centimeters (cc) If you are finding the volume of an object, then you are using the 3 numbers of the volume formula (length x width x height): 6 m x 2m x 4m = 48m 3

Why do we cube meters? (m 3 ) We cube meters to show the solid object is 3-dimensional (like a box) Since liquids fill up a container, we automatically know it is volume.

Lab Measurement Instruments A meter stick is used to find length A balance is used to find mass. A scale is used to find weight. A graduated cylinder is used to find volume. The bottom of the curve of the graduated cylinder is called the meniscus. Liquids are heated in a flask using tongs.

Volume of a Irregular-Shaped Object If you have an object that you cannot measure with a meter stick (such as a rock), you would 1) Fill a cylinder with water and measure from the meniscus 2) Put in the rock and measure the meniscus 3) Find the difference ( in mL)

How Mass and Volume Affect Density http://www.youtube.com/watch ?v=h5Mkt46Pwog&safety_mode =true&persist_safety_mode=1& safe=active

Density Density – This is a physical property - “thickness” of matter. It is the amount of mass per unit of volume. Formula: mass divided by volume = m/v Example: an object that has a mass of 28g and a volume of 7 28 g 28g 7 ml= 4 g/ ml OR 7 cm 3 = 4g/ cm 3 Question: Does a larger object always have greater density? Which has a greater density, a baseball or a beach ball? WHEN YOU HAVE GREATER MASS COMPARED TO A SMALLER VOLUME, THE HIGHER THE DENSITY. Rate is a ratio between 2 different types of measurement. For example: density is a ratio between mass and volume.

Density: What if Animals Were Round? http://www.youtube.com/watch?v=yltlJ EdSAHw

How the Titanic Sank http://www.youtube.com/watch ?v=G8ey_RBdxYM&safety_mod e=true&persist_safety_mode=1 &safe=active

Density is a Physical Property Every element on the periodic table can be identified by a special physical property. Every element has its own specific density. In other words, it doesn’t matter how large or small the sample is, each element would have a specific density. So, if you wanted to identify an element, what are the two things you could find out about it that would prove what the element is?

SI Temperature Temperature: In SI, Celsius is normally used instead of Fahrenheit Conversion: o C = ( o F-32) 1.8 Freezing Point (water): 0 o C Boiling Point (water): 100 o C For extreme temperatures we use Kelvin: K = o C + 273 Absolute zero: −273.15 o C or 0 K (no heat at all) Kelvin does not use a degree mark.

Temperature Kelvin is different from Fahrenheit and Celcius in that it does not use a degree superscript ( o ). To remember Kelvin, think of the magic Kelvin number: 273. Differences between Fahrenheit, Celcius and Kelvin: o F – based on 12 (random) o C – most common temp. based on 10 K – no degree mark (C +273) extreme

Absolute Zero Absolute Zero is the temperature in which there is no molecular movement, because there is absolutely no heat energy. Absolute Zero is “as cold as it gets.” Theoretically, Absolute Zero is achieved at 0 K (or -273 o C.) It does not occur naturally, but there have been severa l attempts to achieve it in a lab setting: http://www.youtube.com/watch?v=K1ZWN1rqTX4

Into to the Metric System http://www.youtube.com/watch?v=U04n HNUMfPA

Metric System Prefixes (Memorize These!) In the metric system, the prefixes of units (meters, grams and liters) indicate if you are dealing with whole units (a – e), or fractions of one unit (f – I): a. mega- (M) 1 000 000 x b. kilo- (k) 1 000 x c. hecto- (h) 100 x d. deka- (da) 10 x e. Main Unit 1 x (meter, gram, liter) f. deci- (d) 0.1 x(1/10) g. centi- (c) 0.01 x (1/100) h. milli- (m) 0.001 x (1/1000) i. micro- (u) 0.000 000 001 x

Metric System Conversion How do you convert from one unit to another? First, they must be related. For example, you can convert inches to feet or yards, but can you convert inches to pints or quarts? It is the same with metrics. You can convert meters to meters, grams to grams, or liters to liters (or cm 3 ), but you can’t convert meters to grams or liters.

Metric Conversion 0.050 cm to _____ m (1/500 of a centimeter = how many meters?) Step 1: Convert larger unit to the smaller units (how many centi are in a meter?): 100 0.050 divided by 100 = 0.0005 0.050 cm =. 0005 meters

Metric Conversion Steps 1) Which unit is the smallest? 2) How many of that small unit can go into one of the large units? Write that down, because the # of 0’s is how many places you are moving. 3) If the you looking at a fraction (small units into large), move the decimal to the left; 4) If you are looking at multiple units (large into small), move the decimal to the right.

Metric Conversion Look again: 0.050 cm = ? m 0.050 divided by 100 = 0.0005 Answer: 0.00050 m Get rid of the first and last 0 (no value) Answer:.0005 m Did you notice that, because the metric system is based on 10, you really only had to move the decimal place? You don’t have to actually divide!

Metric Conversion When you divide or multiply by *1000, move the decimal 3 places *100, move the decimal 2 places *10, move the decimal 1 place If you are going from a small unit to a larger unit (i.e. centi to a whole meter) move the decimal to the left If you are going from a larger unit to a smaller unit (i.e. meter to centi) move the decimal to the right