Density Lab

Problems: 1. To find the density of various objects and determine whether they willfloat or sink.

  1. Understand why some objects/liquids float within other liquids.
  2. Explain what buoyant force is.
  3. Find the density of an 8th grader.
  4. Investigate Science Standards: 8. All objects experience a buoyant force when immersed in a fluid. As a basis for understanding this concept: 8a. Students know density is mass per unit volume. 8b. Students know how to calculate the density of substances (regular and irregular solids and liquids) from measurements of mass and volume. 8c. Students know the buoyant force on an object in a fluid is an upward force equal to the weight of the fluid the object has displaced. 8d. Students know how to predict whether an object will float or sink. 9e. Construct appropriate graphs from data and develop quantitative statements about the relationships between variables. 9f. Apply simple mathematic relationships to determine a missing quantity in a mathematic expression, given the two remaining terms (including speed = distance/time, density = mass/volume, force = pressure × area, volume = area × height).

Hypothesis/ predictions:

1. If the density of a whole crayon is ____g/cm3 than the density of half acrayon is _____g/cm3.

2. You are given the following liquids: honey, baby oil, salt water, alcohol, vegetable oil, corn syrup, and Dawn dish soap.

Order the liquids from most dense to least dense. Why did you list the liquids in that order?

3.What is the density of a person?______What is the density of water?______Why do people

who swim in the Dead Sea float effortlessly? Why do they not float so effortlessly in the Pacific Ocean? Or in a swimming pool?

Materials:marbles, crayons, blocks of different materials, graduated cylinder, pan, 30ml, 250ml beakers or overflow cylinders, straw, vegetable oil, baby oil, corn syrup, honey, alcohol, salt water, tape, balance, 8th grader, barrel, buckets

Procedure:

Make sure you answer the hypothesis predictions first before you start the lab.

1. Using your balance find the mass of the following objects: 1 marble, different blocks, 1 whole crayon without the wrapper.

2. Find the volume of one marble using the string method. Remember that to

find the radius you will need to measure the circumference and divide by 2 Then you will need to use the volume formula for a sphere from your agenda or the bottom of this lab.

  1. Fill a graduated cylinder to 20ml exactly. Place the marble in the graduated cylinder. Notice how many mL that the marble raised the water level. Record the change in volume by water displacement of the marble.
  2. Find the volume of the crayon using math. (Hint: What shape is a crayon? -you can snap off a point if it happens to be present to make it more of the appropriate shape)
  3. Now find the volume of the crayon using the water displacement method. Fill a 50 ml graduated cylinder with 30ml of water. Make sure the meniscus line (the bottom of the curve) is on the 30 ml line. Place object into graduated cylinder. Notice the amount of water displaced by the object. Write down the difference or change in volume that the crayon displaced. The water displaced is the volume of the object.
  4. Take the whole crayon and break it in half. Find the mass of ½ the crayon, then find its volume in which method you like best.
  5. Find the volume of a block using math. (Hint: What shape is a block?Measure all sides.)
  6. Fill an overflow can until water just starts to flow through the hole. Place a block in the can, carefully catching all the water that flows out into a graduated cylinder. Record this value for volume by water displacement.
  7. Repeat this process with all the blocks. If some blocks are smaller use the best method to discover its volume.
  8. Find the mass and volume of an object of your choice. Record your results.

Liquid Density

11. Take a straw and tape the bottom shut.

12. With a plastic dropper add 8 drops of the following liquids in the order provided. When adding each drop make sure the liquid slides down the side of the straw not directly down the middle.

  1. orange-honey
  2. red- corn syrup
  3. blue- dish soap
  4. green- salt water
  5. yellow- oil
  6. purple – alcohol
  7. clear-baby oil

13. Draw a picture of the straw with the each color liquid labeled.

  1. Write down in your conclusion why each liquid settled like it did.

Density of an 8th grader

  1. Find the mass of each 8th grader in pounds and write their name down in your table.
  2. Convert pounds into grams. 1 Lb. = 454 g
  3. Put 8th grader in barrel, have them slowly sit down into barrel.
  4. Collect displaced water and measure it in graduated cylinders.
  5. Calculate Density.

Data:

object / Mass (g) / Volume (cm3)
Using Math / Density (g/cm3)
Using Math / Volume (mL)
Using water displacement / Density (g/mL)
Using water displacement
  1. 1 marble

  1. 1 crayon

  1. ½ crayon

  1. Block- Aluminum

  1. Block- Steel

  1. Block- Brass

  1. Block- Copper

  1. Block- Acrylic

  1. Block-Oak

  1. Block- Nylon

  1. Block-Pine

  1. Block- Poplar

13.Block- Polyvinyl Carbonate
14.Object of your choice:______
8th grader
Name / Lbs / Multiply lbs by 454 = g / Volume (ml) / Density (g/ml)
1.
2.
3.
4.
5.
6.
15.Average

Important Hints: r = circumference/ 2volume of a sphere = 4r3/3

volume of a cylinder = r2h volume of a cube = s3

1Lbs = 454 g 1mL = 1 cm3

Density = Mass / Volume

Write a short conclusion (2nd R only) about all three parts. Make sure you mention your data and answer the problems and hypothesis/prediction questions. Don’t forget to include your drawing of the straw in color! Draw a graph that compares the density of all 15 objects. Put the objects in order from smallest density to largest density.