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)

Estimation When you estimate, you look at the place value to the right of the place value you are estimating to. If that number is 5 or above, then you will raise the place value by 1 number: Examples: tenths: 6.43 = 6.4 but 6.45 = 6.5 hundredths: = but = Whole numbers: = 987 but = 170

Organizing Data Mean, median and mode: When you analyze a set of data Mean = average (add up numbers and divide by the amount of numbers you added) = / 3 = 5 (mean) median = the number that represents the “middle” of the data. YOU HAVE TO PUT THEM IN ORDER FROM SMALLEST TO LARGEST: 6.2, 7.5, 4.3 put in order: (median is 6.2) mode = when you have a number that appears the most often 23.7, 14.9, 23.7, 66.1 mode = 23.7 range = subtract the smallest number from the largest: 66.1 – 14.9= 51.6

Graphs III. Graphs Used to visually see a change or comparison in data Line graph – shows a change over time

Bar Graphs Bar graph – shows a comparison between 2 or more objects or event

Circle Graphs Circle graph – uses a circle to show a breakdown to show percentages (out of 100%). Colors and patterns are often used to show the differences.

Computing Percentages for a Circle Graph There are 360 o in a circle. If you have 15% to shade, then 360 o x.15 = 54 o So you would mark the 54 o with a protractor.

The Metric System 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!

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

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 ?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.

How the Titanic Sank ?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) o F = ( o C x 1.8) Freezing Point (water): 0 o C Boiling Point (water): 100 o C For extreme temperatures we use Kelvin: K = o C Absolute zero: − 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:

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 o C.) It does not occur naturally, but there have been severa l attempts to achieve it in a lab setting:

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) x b. kilo- (k) 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) x (1/1000) i. micro- (u) x

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

Metric Conversion 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?): divided by 100 = cm = 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: cm = ? m divided by 100 = Answer: 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!

Scientific Measurements: Scientific Notation and Dimensional Analysis – HS Phyiscal Science Part II

Scientific Notation Scientific notation is a way to make these numbers easier to work with. In scientific notation, you move the decimal place until you have a number between 1 and 10. Then you add a power of ten that tells how many places you moved the decimal.

Scientific Notation In scientific notation, 2,890,000,000 becomes 2.89 x How? Remember that any whole number can be written with a decimal point. For example: 2,890,000,000 = 2,890,000,000.0 Now, move the decimal place until you have a number between 1 and 10. If you keep moving the decimal point to the left in 2,890,000,000 you will get Next, count how many places you moved the decimal point. You had to move it 9 places to the left to change 2,890,000,000 to You can show that you moved it 9 places to the left by noting that the number should be multiplied by x 10 9

Scientific Notation Scientific notation can be used to turn into 7.3 x First, move the decimal place until you have a number between 1 and 10. If you keep moving the decimal point to the right in you will get 7.3. Next, count how many places you moved the decimal point. You had to move it 6 places to the right to change to 7.3. You can show that you moved it 6 places to the right by noting that the number should be multiplied by x =

Scientific Notation Remember: in a power of ten, the exponent—the small number above and to the right of the 10—tells which way you moved the decimal point. A power of ten with a positive exponent, such as 10 5, means the decimal was moved to the left. A power of ten with a negative exponent, such as 10 -5, means the decimal was moved to the right.

Converting to Standard Notation 1.5 x 10 4 Since the exponent is positive, we know that we are going to increase the number by moving the decimal to the right 4 places (from the far end on left): 15,000

Converting to Standard Notation 1.2 x Since the exponent is negative, we know that we are going to decrease the number by moving the decimal to the left 4 places:.00012

Dimensional Analysis Dimensional Analysis allows you to solve many problems by examining the relationship of one unit to another. This will help you in high school when you are using very large to very small amounts (and vice-versa). For example: How many seconds are in one day? Step 1: What do I need to know? sec day Remember, you start with seconds and move up to a day.

Dimensional Analysis Here’s How: Zn5MLKvk

Dimensional Analysis We are going to write a conversion statement, starting with seconds to minutes: 60 sec 60 min24 hrs 1 X 1 hour X 1 day Now, cancel out the units that are the same in the numerator and denominator: 60 sec 60 min24 hrs 1 X 1 hour X 1 day

Dimensional Analysis After canceling out the units, multiple across: 60 secs 60 mins24 hrs86,400 sec 1 min X 1 hr x 1 day = 1 Day Try this: 4.4 km = _____ cm

Dimensional Analysis 4.4 km = _____ cm 4.4 km 1000 m100 cm 1 X 1 km X 1 m - Cancel out the like units - Multiply out the numbers: 4.4 x 1000 x100 1 Since there are 5 zeros, use Scientific Notation: 4.4 x 10 5 km Easy!

Dimensional Analysis A dog walks 457 meters away from home. If there are 1000 meters in a kilometer, how many kilometers away from home did the dog wander? First, what are we trying to find out?457 m 1 km 457 m 1 km 1 km1000 m cancel out the same units 457 m 1000 m =.457 km