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MEASUREMENTS
HTTP://WWW.BRAINPOP.COM/SCIENCE/MATTERANDCHEMISTRY/MEASURINGMATTER/PREVIEW.WEML
MEASUREMENT IN CHEMISTRY
IN CHEMISTRY WE
¨ DO EXPERIMENTS
¨ MEASURE QUANTITIES
¨ USE NUMBERS TO REPORT MEASUREMENTS
METRIC SYSTEM (SI)
• IS A DECIMAL SYSTEM BASED ON 10
• USED IN MOST OF THE WORLD
• USED BY SCIENTISTS AND HOSPITALS
* SI means System International
UNITS IN THE METRIC SYSTEM
LENGTH METER M
VOLUME LITER L
MASS GRAM G
TEMPERATURE CELSIUS °C
METRIC PREFIXES• METRIC UNITS• THE METRIC SYSTEM HAS PREFIX MODIFIERS THAT
ARE MULTIPLES OF 10.
Prefix Symbol Factor Number Factor Word
Kilo- k 1000 Thousand
Hecto- h 100 Hundred
Deca- da or dk 10 Ten
Unit m, l, or g 1 One
Deci- d .1 Tenth
Centi- c .01 Hundredth
Milli- m .001 thousandth
PLACE VALUES OF METRIC PREFIXES
Thousand
Hundred Ten One Tenth
Hundredth
Thousandth
kmkgkL
hmhghL
dkmdkgdkL
mgL
dmdgdL
cmcgcL
mmmgmL
STATING A MEASUREMENT
IN EVERY MEASUREMENT THERE IS A
¨ NUMBER FOLLOWED BY A
¨ UNIT FROM A MEASURING DEVICE
THE NUMBER SHOULD ALSO BE AS PRECISE AS THE
MEASUREMENT!
UNCERTAINTY IN MEASUREMENT• SCIENTIFIC MEASUREMENTS ARE
REPORTED SO THAT EVERY DIGIT IS CERTAIN EXCEPT THE LAST, WHICH IS ESTIMATED.
SOME TOOLS FOR MEASUREMENT
Which tool(s) would you use to measure:A. temperatureB. volumeC. timeD. weight
INTENSIVE VS. EXTENSIVE PROPERTIES
• INTENSIVE—INDEPENDENT OF THE AMOUNT OF SUBSTANCE
THEY DO NOT DEPEND ON THE AMOUNT OF MATTER
COLOR, ODER, LUSTER, MALLEABILITY, CONDUCTIVITY, HARDNESS, MELTING/ FREEZING POINT, BOLING POINT, AND DENSITY
• EXTENSIVE—DEPENDENT UPON THE AMOUNT OF SUBSTANCE
THEY DEPEND ON THE AMOUNT OF MATTER PRESENT
MASS, WEIGHT, VOLUME, AND LENGTH
You can measure the length of ANYTHING!
When we measure length we measure how long something is.
Standard units
Millimeters (mm) Centimeters
(cm)
Meters (m) Kilometers (km)
MASS VS. WEIGHT
• MASS: AMOUNT OF MATTER (GRAMS, MEASURED WITH A BALANCE)
• WEIGHT: FORCE EXERTED BY THE MASS, ONLY PRESENT WITH GRAVITY (POUNDS, MEASURED WITH A SCALE)
Can you hear me now?
TOOLS FOR MEASURING MASS
• THE TRIPLE BEAM BALANCE
HOW TO USE A TRIPLE BEAM BALANCE
• 1) MAKE SURE THAT THE BALANCE SCALE IS AT ZERO.• 2) PLACE OBJECT ON BALANCE SCALE THE LARGES AND MOVE THE
LARGEST RIDER ONE NOTCH AT A TIME UNTIL THE BEAM DROPS. MOVE THE RIDER BACK ONE NOTCH (MAKE SURE IT LOCK IN PLACE)
• 3) MOVE THE NEXT LARGEST RIDER UNTIL THE BEAM DROPS. BACK IT UP ONE NOTCH.
• 4) MOVE THE SMALLEST RIDER UNTIL THE BEAM SWINGS EQUALLY ABOVE AND BELOW THE ZERO MARK.
• 5) ADD UP ALL THE NUMBERS TO FIND THE MASS!
WHAT IS VOLUME?
• VOLUME IS THE MEASURE OF THE CAPACITY OF A CONTAINER.
• IT IS THE MEASURE OF HOW MUCH A CONTAINER OF A PARTICULAR SHAPE WILL HOLD - LIQUIDS, DRY SUBSTANCES, ETC.
WHAT’S THE FORMULA?
The formula for finding the volume of a rectangle is ….
L x W x H = Volume
This means we take the length times the width, then multiply that by the height.
Measuring Volume
Top Image: http://www.tea.state.tx.us/student.assessment/resources/online/2006/grade8/science/images/20graphicaa.gifBottom Image: http://morrisonlabs.com/meniscus.htm
We will be using graduated cylinders to find the volume of liquids and other objects.
Read the measurement based on the bottom of the meniscus or curve. When using a real cylinder, make sure you are eye-level with the level of the water.
What is the volume of water in the cylinder? _____mL
What causes the meniscus?
A concave meniscus occurs when the molecules of the liquid attract those of the container. The glass attracts the water on the sides.
Measuring Liquid Volume
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Pay attention to the scales for each cylinder.
VOLUME DISPLACEMENT
33 ML
25 ML
A SOLID DISPLACES A MATCHING VOLUME OF WATER WHEN THE SOLID IS PLACED IN WATER.
Measuring Solid Volume
Click here for an online activity about volume. Choose Lessons Volume & Displacement
10 cm
9 cm
8 cm
We can measure the volume of regular object using the formula length x width x height.
_____ X _____ X _____ = _____
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We can measure the volume of irregular object using water displacement.
Amount of H2O with object = ______
About of H2O without object = ______
Difference = Volume = ______
Density is defined as mass per unit volume. It is a measure of how tightly packed and how heavy the molecules are in an object. Density is the amount of matter within a certain volume.
Density
WHICH ONE IS MORE DENSE?
DEMONSTRATION: PEOPLE IN A SQUARE
HOW ABOUT THIS: WHICH SQUARE IS MORE DENSE?
WHICH ONE IS MORE DENSE?
HTTPS://WWW.YOUTUBE.COM/WATCH?V=ZHL68D9BPIW
WATER AND ICE HAVE DIFFERENT DENSITIES WHICH ONE IS MORE DENSE?
TO FIND THE DENSITY
3- DIVIDE DENSITY = MASS G VOLUME C³
2- Find the volume of the object
1- Find the mass of the object
ALWAYS REMEMBER
UNITS!
DENSITY - AN IMPORTANT AND USEFUL PHYSICAL PROPERTY
Density mass (g)volume (cm3)
Density mass (g)volume (cm3)
Mercury
13.6 g/cm3 21.5 g/cm3
Aluminum
2.7 g/cm3
Platinum
DENSITYDENSITY• DENSITY IS AN
INTENSIVE PROPERTY OF MATTER.
• DOES NOT DEPEND ON QUANTITY OF MATTER.
• TEMPERATURE
• CONTRAST WITH EXTENSIVE
• DEPENDS ON QUANTITY OF MATTER.
• MASS AND VOLUME.
Styrofoam
Brick
PROBLEM A PIECE OF COPPER HAS A MASS OF 57.54 G. IT IS 9.36 CM LONG, 7.23 CM WIDE, AND 0.95 MM THICK. CALCULATE DENSITY (G/CM3).
Density mass (g)volume (cm3)
Density mass (g)volume (cm3)
If you have 2 or more substances,
the MORE dense substance will be on bottomThe LESS dense substance will be on top
LecturePLUS Timberlake 31
TEMPERATURE
PARTICLES ARE ALWAYS MOVING.
WHEN YOU HEAT WATER, THE WATER MOLECULES MOVE FASTER.
WHEN MOLECULES MOVE FASTER, THE SUBSTANCE GETS HOTTER.
WHEN A SUBSTANCE GETS HOTTER, ITS TEMPERATURE GOES UP.
TEMPERATURE IS MEASURED IN DEGREES.
Temperature is measured on two scales: Celsius and Fahrenheit.
98.637 CF
The lower case “C” is the symbol for the
Celsius scale.
C
We will use Celsius
