# Chemistry/Density

### From WikiEducator

**CALCULATING THE DENSITY OF WATER, A BLOCK OF WOOD AND A ROCK SAMPLE**

**PURPOSE:** The purpose of this experiment is to find the density of distilled water, the density of a sample of wood, the density of a rock sample and discover how density determines whether an object sinks or floats in water.

**MATERIAL:**

- balance
- block of wood
- distilled water large beaker
- graduated cylinder
- centimetre ruler
- rock sample

**DATA:**

- mass of 25 mL graduated cylinder = _______________________

- mass of graduated cylinder + 25.0 mL of water = ____________________

- number of rock sample = __________

- mass of rock sample = _______________________

- volume of water in 250 mL graduated cylinder =_______________________

- volume of water in 250 mL graduated cylinder after adding rock = ______________________

- what happens to rock when placed in water: _________________________

- number of wood block = __________

- mass of wood block = _______________________

- dimensions of wood block: length = _______________________

- what happens to wood block when placed in water: ___________________________________

PROCEDURE:
1. Weigh an empty, dry 25 mL graduated cylinder. 2. Fill the graduated cylinder to 3. Obtain a dry rock sample and 4. Pour an easily measured volume of water into a 250 mL graduated cylinder and 5. Tilt the graduated cylinder at a 45o angle and carefully slide the rock sample down into the water, so as to avoid splashing out any water. 6. Obtain a wood block and 7. Measure the length, width and height of the wood block and 8. Place the wood block in a large beaker half–filled with water. |

**DISCUSSION:**

*IMPORTANT NOTE:* In all the questions and calculations that follow, you **must** say what you are doing or calculating. If numbers are being subtracted or multiplied together the numbers involved in the calculation **must** be shown and the result written down; if a special equation is being used the equations **must** be shown, the numbers being used **must** be shown as they are used in the equation and the results of the calculation **must** be shown.

1. (a) Calculate the mass of the water in the 25 mL graduated cylinder.

(b) Calculate the density of the sample of distilled water using the following formula. Round your answer off to **three** decimal places.

2.(a) Calculate the volume of the rock sample.

(b) Calculate the density of the rock sample using the following formula. Round your answer off to **two** decimal places.

3. (a) Calculate the volume of the wood block. The units are “cm^{3} ”. What is this volume when expressed in “mL”?

(b) Calculate the density of the wood block using the following formula. Round your answer off to **three** decimal places.

4. Fill in the following table.

Object | Density of Object | Density of Water | Does object float or sink in water? | Is object’s density greater or less than water’s density? |
---|---|---|---|---|

rock | ||||

wood |

5. Write out and complete the following sentences using the information in the above table.

**Objects having a density greater than the density of water will _____________ when placed in water. Objects having a density less than the density of water will _____________ when placed in water.**