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 THT DENSITY IS ONE CHARACTERISTIC
  PROPERTY OF MATTER.

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LETS READ.

• PAGE 16 USEFUL CALCULATIONS

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INQUIRY 2.1- FINDING THE MASS OF WATER

• GETTING STARTED
• WHAT IS THE DIFFERENCE BETWEEN MASS.

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• AND VOLUME???

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• 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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TOTE TRAY MATERIALS

• 1 TOTE TRAY
• 1 BLOCK OF WAX
• 1 BLOCK OF TRANSPARENT PLASTIC
• 1 BLOCK OF WHITE PLASTIC
• 1 BLOCK OF ALUMINUM
• 1 STEEL SCREW
• 1 COPPER CYLINDER
• 1 NYLON SPACER
• 2 100-Ml GRADUATED CYLINDERS
• METRIC RULER
• ELECTRONIC BALANCE

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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 10mL

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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.

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• 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.
• 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

• MEASURING THE DENSITIES OF REGULAR OBJECTS

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PROCEDURE

• COLLECT THE TRAY OF MATERIALS
• CHECK IT AGAINST THE MATERIALS FOR INQUIRY 2.1
• REMOVE THE BLOCKS OF WAX, TRANSPARENT PLASTIC,
  WHITE PLASTIC, AND ALUMINUM FROM THE TOTE TRAY.

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• DO YOU THINK ALL OF THE BLOCKS HAVE THE SAME
  DENSITY? RECORD THIS AS YOUR HYPOTHESIS IN YOUR
  NOTEBOOK.
• WHAT EVIDENCE DO YOU HAVE TO SUPPORT YOUR ANSWER?
• WHAT MEASUREMENTS WILL OU NEED TO MAKE TO TEST
  YOUR HYPOTHESIS?
• WHAT IS THE FORMULA FOR FINDING DENSITY?

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• WORK WITH YOUR LAB PARTNERS TO FIND THE DENSITY
  OF EACH OF THE BLOCKS AND RECORD YOUR RESULTS ON
  STUDENT SHEET 2.2.
• COMPARE YOUR CALCULATIONS WITH THE OTHERS IN YOUR
  GROUP.
• IF YOUR CALCULATED DENSITITES DONT MATCH (TO
  WITHIN 1 g/cm3), REPEAT YOUR CALCULATIONS.

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STUDENT SHEET QUESTIONS

• ANSWER THE FOLLOWING AS A GROUP AND RECORD YOUR
  ANSWERS ON YOUR STUDENT SHEET.
• ARE THE DENSITIES OF THE DIFFERENT SUBSTANCES THE
  SAME OR DIFFERENT?
• HOW COULD THIS INFORMATION BE USED TO IDENTIFY
  THE SUBSTANCE FROM WHICH AN OBJECT IS MADE?

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INQUIRY 2.3 DENSITY OF IRREGULAR OBJECTS

• REMOVE THE STEEL SCREW, COPPER CYLIN, DISDER, AND
  NYLON SPACER FROM THE TRAY.
• IN YOUR GROUPS, DISCUSS HOW YOU COULD FIND THE
  DENSITY OF EACH OF THESE OBJECTS.
• BE PREPARED TO SHARE YOUR THOUGHTS AFTER 5
  MINUTES.

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• ON STUDENT SHEET 2.3, DRAW A SERIES OF SIMPLE
  DIAGRAMS SHOWING HOW YOU ARE GOING TO FIND OUT
  THE MASS AND VOLUME OF THE OBJECTS. YOU MAY NOT
  NEED TO USE ALL THE BOXES.
• DEVISE A TABLE IN WHICH TO RECORD YOUR DATA.
  HINT YOULL NEED A COLUMN FOR EACH OF THE
  MEASUREMENTS YOULL MAKE. REMEMBER DENSITYM X V

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• BE SURE TO USE THE CORRECT UNITS OF MEASURE WHEN
  LABELING THE COLUMNS.
• FIND THE MASS, VOLUME, AND DENSITY OF EACH
  OBJECT. FIND THE MASS OF EACH OBJECT BEFORE YOU
  PUT THEM IN THE WATER. WHY??

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ANSWER THE QUESTIONS ON STUDENT SHEET 2.3

• 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 DID THE DENSITIES OF THE OBJECTS COMPARE WITH
  THE DENSITY OF WATER?

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REFLECTIONS-Record these answers using the
information from the inquiries. A score will be
taken.

• 1. WHAT IS THE DIFFERENCE BETWEEN MASS AND
  VOLUME?
• 2. WHAT UNITS DID YOU USE TO MEASURE MASS AND
  VOLUME?
• 3. HOW DID YOU CALCULATE THE DENSITY OF AN
  OBJECT?
• 4. WHAT UNITS DID YOU USE TO MEASURE DENSITY?
• 5. IF 2 OBJECTS ARE MADE FROM THE SAME
  SUBSTANCE, WILL THEY HAVE THE SAME DENSITY?

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• READ PG. 20 DENSITY AS A CHARACTERISTIC
  PROPERTY AND
• PG. 21 MASS OR WEIGHT? AFTER YOUVE SEEN THIS
  CLIP.