DETERMINING DENSITY

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LESSON 2

• DETERMINING DENSITY

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OBJECTIVES

• EXPLAIN THE DIFFERENCE BETWEEN MASS AND VOLUME.
• MEASURE MASS, IN GRAMS, USING AN ELECTRONIC
  BALANCE.
• MEASURE THE VOLUME OF A LIQUID, IN CUBIC
  CENTIMENTERS (cm3) (or milliliters), USING A
  GRADUATED CYLINDER.
• CALCULATE THE MASS OF 1.0 cm3 OF A SUBSTANCE.

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• RECOGNIZE THAT THE MASS OF A UNIT VOLUME OF A
  SUBSTANCE IS ALSO CALLED ITS DENSITY.
• USE EXTERIOR DIMENSIONS TO CALCULATE THE VOLUME
  OF REGULAR BLOCKS.
• MEASURE THE VOLUME OF OBJECTS BY USING
  DISPLACEMENT OF WATER.
• RECOGNIZE THAT DENSITY IS ONE CHARACTERISTIC
  PROPERTY OF MATTER.

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LETS READ.

• PAGE 16 USEFUL CALCULATIONS

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INQUIRY 2.1 GETTING STARTED

• WHAT IS THE DIFFERENCE BETWEEN MASS AND VOLUME?
• COLLECT A TOTE TRAY CONTAINING THE MATERIALS FOR
  THIS INQUIRY.
• LETS LOOK AT HOW TO USE AN ELECTRONIC BALANCE.
• TURN TO PG. 16 IN YOUR S.G. AND DISCUSS QUESTION
  2 WITH YOUR GROUP.

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• A. WHAT IS THE UNIT OF MEASURE FOR THE GRADUATED
  CYLINDER?
• Answer mL
• B. WHAT IS THE MAXIMUM VOLUME IT CAN MEASURE?
• Answer 250 mL
• C. WHAT IS THE MINIMUM VOLUME IT CAN MEASURE?
• Answer 10mL
• D. WHAT IS THE NUMBER OF UNITS MEASURED BY THE
  SMALLEST DIVISION ON ITS SCALE?
• Answer 1mL

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• In this experiment, you will investigate the mass
  of different volumes of water.
• How could you find the mass of 50 mL of water by
  using the graduated cylinder and the electronic
  balance?
• Lets share ideas and put the results on your
  student sheet on 1.
• 1. Put exactly 50 mL of water into the graduated
  cylinder. Make sure the graduate is on a level
  surface and you are reading with the bottom of
  the meniscus.

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• 2. Find the mass of the graduated cylinder plus
  water.
• 3. Subtract the mass of the graduated cylinder
  from the mass of the graduated cylinder plus
  water.

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PONDER THE FOLLOWING

• The mass of 1 cm3 of water remains the same
  regardless of the volume of water measured.
• The mass of 1 cm3 of water remains the same
  regardless of the mass of water measured.
• Mass per unit volume is called density and can be
  measure in grams per cubic centimeters.
• Changing the mass or volume of water does not
  change its density.
• The density of water is a characteristic property
  of water.

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INQUIRY 2.2

• REMOVE THE FOLLOWING MATERIALS
• FROM YOUR TOTE TRAY
• BLOCKS OF WAX
• TRANSPARENT PLASTIC
• WHITE PLASTIC
• ALUMINUM BLOCK

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• DO YOU THINK ALL OF THESE BLOCKS HAVE THE SAME
  DENSITY?
• WHAT EVIDENCE DO YOU HAVE TO SUPPORT YOUR ANSWER?
• WHAT MEASUREMENTS WILL YOU NEED TO TEST Y OUR
  HYPOTHESIS?

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• WORK WITH YOUR GROUPS TO
• USE THE RULER TO MEASURE THE BLOCKS. CALCULATE
  THE VOLUME OF EACH BLOCK IN CUBIC CENTIMETERS.
• REMEMBER VOLUME LENGTH x WIDTH x HEIGHT .
  RECORD YOUR ANSWERS AND THE UNITS USED (cm3).
• USE THE BALANCE TO MEASURE THE MASS OF THE
  BLOCKS.
• REMEMBER RECORD YOUR ANSWERS USING GRAMS (g).

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• DETERMINE THE DENSITY OF EACH THE BLOCKS. BE
  SURE THAT EACH PERSON IN YOUR GROUP GETS A CHANCE
  TO MAKE EACH MEASUREMENT AND CALCULATION.
• REMEMBER DENSITY MASS DIVIDED BY VOLUME.
  RECORD YOUR ANSWERS USING g/cm3.

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Answer the following on your student sheet.

• Are the densities of the different substances
  the same or different?
• Answer different
• How could this information be used to identify
  the substance from which an object is made?
• Answer Every substance has a different density.
  You can compare the density to a known density
  list.

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INQUIRY 2.3 DENSITIES OF IRREGULAR OBJECTS

• REMOVE THE FOLLOWING THREE OBJECTS FROM YOUR TOTE
  TRAY
• STEEL SCREW
• COPPER CYLINDER
• BLACK NYLON SPACER

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• HOW WOULD YOU FIND THE DENSITY OF EACH OF THESE
  OBJECTS?
• HINT REMEMBER INQUIRY 1.2
• DRAW A SERIES OF SIMPLE DIAGRAMS IN THE BOXES ON
  STUDENT SHEET 2.3, SHOWING HOW YOU ARE GOING TO
  FIND THE MASS AND VOLUME OF THE OBJECTS.
• IN YOUR GROUP DEVISE A TABLE IN WHICH TO RECORD
  YOUR DATA. INCLUDE A PLACE FOR ALL OF YOUR
  MEASUREMENTS, CALCULATIONS, AND THE DENSITY OF
  THE OBJECTS.

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• WHEN YOUR HAVE DEVISED YOUR TABLE, USE A RULER TO
  DRAW YOUR TABLE ON STUDENT SHEET 2.3.
• FIND THE MASS, VOLUME, AND DENSITY FOR EACH OF
  THE OBJECTS. FIND THE MASS BEFORE YOU PUT THE
  OBJECTS IN THE WATER.
• COMPLETE YOUR DATA TABLE.

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ANSWER THE FOLLOWING ON YOUR STUDENT SHEET

• ARE ANY OF THE BLOCKS FROM INQUIRY 2.2 OR OBJECTS
  FROM THIS INQUIRY MADE FROM THE SAME SUBSTANCE?
• HOW DID YOU REACH YOUR CONCLUSION?
• HOW DO THE DENSITIES OF THE OBJECTS COMPARE WITH
  THE DENSITY OF WATER?

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GLOSSARY

• DENSITY THE MASS PER UNIT VOLUME OF AN OBJECT.
• CHARACTERISTIC PROPERTY - A PROPERTY THAT IS
  INDEPENDENT OF MASS, VOLUME, AND SHAPE
• DISPLACEMENT THE VOLUME OR WEIGHT OF A FLUID
  THAT IS MOVED BY A FLOATING BODY WITH THE WEIGHT
  OF THE DISPLACED FLUID BEING EQUAL TO THAT OF THE
  DISPLACING BODY.

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• MASS THE AMOUNT OF MATTER IN AN OBJECT.
• VOLUME A MEASURE OF SPACE TAKEN UP BY SOME
  MATTER.
• MENISCUS THE CURVED UPPER SURFACE OF THE WATER
  IN THE GRADUATED CYLINDER.
• WEIGHT - A MEASURE OF THE FORCE OF GRAVITY.