Density



Density Lab Make Up

Density is a physical property of a substance and is often used to identify what the substance is. Since mass is usually expressed in grams and volume in cubic centimeters, density is expressed in g/cm3.

We can calculate density using the formula:

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You can calculate the mass of an object using a triple beam balance or an electronic scale. You can calculate the volume of a regular shaped solid using the formula V = l x w x h.

When referring to the density of a solid we use g/cm3 or kg/m3.

When referring to the density of a liquid we use g/mL or kg/L.

The density of water is said to be 1 g/mL. If something is less dense than water it will float and if it is denser than water it will sink.

Pre-lab:

1. Define density.

2. Write the mathematical expression of density (the formula).

3. What units are associated with density?

4. The mass of a block is 2.70 g. What will be the density of a block with a volume of 1.35 cm3? Show work below.

Purpose:

In this activity, you will be dealing with nine cubes of different materials. Each cube is identified by a letter. Look at the picture on the board for reference. Your goal is to show how densities can be used to identify a substance. Make all your measurements first, and then do your calculations later. Be sure to include units!

Materials:

• Triple beam balance

• 9 cubes (A-I) in a tray

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• Beaker filled with water

• Ruler

• Calculator

• Density Chart (on last page)

Procedure: (The data has been provided to you. Analyze the data.)

1. Using the triple beam balance, determine the mass of each cube. Write the measurements in the Data Table 1.

2. Remember V = l x w x h. Using a ruler, determine the volume of each cube and show your work below for cube A. Write the volumes of the blocks in the Data Table 1. (Even though the sizes of the cubes appear to be the same they are not. Make sure to carefully measure.)

Cube 1: side (cm) _______ Calculation (using formula) ________________________

3. Determine the density of each block using the following formula: D = m/V. Fill in Data Table 1.

4. Determine the identity of the block by looking at chart of densities on the board and comparing them with the densities you calculated. Fill in the identities in Data Table 1.

Data Table 1:

|Cube |Mass (g) |Volume |Density |Prediction: |Identity |

| | |(cm3) |(g/cm3) |Sink or Float? | |

|A |18.03 |15.625 | | | |

|B |43.6 |15.625 | | | |

|C |11.5 |15.625 | | | |

|D |22.5 |15.625 | | | |

|E |126.7 |15.625 | | | |

|F |143.4 |15.625 | | | |

|G |146.8 |15.625 | | | |

|H |7.1 |15.625 | | | |

|I |18.1 |15.625 | | | |

5. Place the cubes in order from least dense to most dense. Write your order below:

Least Dense ____ < ____ < ____ < ____ < ____ < ____ < ____ < _____< ____< ____ Most Dense

6. Predict which of the blocks would sink or float in water based upon the densities you calculated above. Fill in your predictions in Data Table 1.

Post Lab Discussion:

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|Now I know that any object with density greater than 1.0g/cm3 will ___________in water. |

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|Is density a qualitative or quantitative observation? ______________________________________ |

|Based upon what you know, circle which one has a higher density |

|Water vs ice |

|Helium filled balloon vs carbon dioxide filled balloon |

|If an egg is placed in tap water, it will sink to the bottom. If an egg is placed in salt water, it will float to the top. Based upon that observation, what can |

|you say about the density of the salt water compared to tap water? |

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|________________________________________________________________________________________ |

|________________________________________________________________________________________ |

|________________________________________________________________________________________ |

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|Think of a real life scenario where knowing the density of an object is important. |

|________________________________________________________________________________________ |

|________________________________________________________________________________________ |

|________________________________________________________________________________________ |

|________________________________________________________________________________________ |

|________________________________________________________________________________________ |

|________________________________________________________________________________________ |

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