Scientific Measurements: The Metric System Part I

Scientific Measurements: The Metric System

Part I

Accuracy – compares a measurement to a true valuePrecision – describes how closely measurements are to each other and how carefully measurements were made

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 = 6.5hundredths: 329.152 = 329.15 but 329.158 = 329.16Whole numbers: 987.3 = 987 but 169.82 = 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) 5 + 5+5 = 15 15 / 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: 4.3 6.2 7.5 (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

GraphsIII. GraphsUsed 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. 

The Metric Systemhttp://www.youtube.com/watch?v=DQPQ_q59xyw&safety_mode=true&persist_safety_mode=1&safe=active

http://www.youtube.com/watch?v=MekxJse2vgs&feature=topics

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 = metervolume = liters (liquids) or centimeters (solid or liquid)mass = gram/kilogram (measured by a balance instrument)

Length, Mass, and Volume

The 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 and Volume

 Volumehttp://www.youtube.com/watch?v=l75FozT3I6o

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

LengthThe 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 m2

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 = 48m3

Lab Measurement Instruments

A meter stick is used to find lengthA 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

DensityDensity – 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

cm3 = 4g/ cm3

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 Experiments

http://www.youtube.com/watch?v=GYoJiMtn_Xc

How the Titanic Sank

http://www.youtube.com/watch?v=G8ey_RBdxYM&safety_mode=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 TemperatureTemperature: In SI, Celsius is normally used instead of Fahrenheit

Conversion: oC = (oF-32) 1.8

Freezing Point: 0 oC Boiling Point: 100 oCIn science, the main SI unit used is Kelvin,

because it can be used for extreme temperatures:

K = oC + 273

Absolute zero: −273.15 oC 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:http://www.youtube.com/watch?v=LB3hvfiPQHY

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 -273o C.) It does not occur naturally, but there have been several attempts to achieve it in a lab setting:http://www.youtube.com/watch?v=K1ZWN1rqTX4

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 xb. kilo- (k) 1 000 xc. hecto- (h) 100 xd. deka- (da) 10 xe. 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 ConversionHow 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 cm3), 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 Steps1) 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 = ? m0.050 divided by 100 = 0.0005Answer: 0.00050 mGet rid of the first and last 0 (no

value)Answer: .0005 mDid 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