Chemistry/Density

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Science 8 Experiment
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. Record the mass in your data table.

2. Fill the graduated cylinder to exactly 25.0 mL. Use a pipet if necessary. If the outside of the glassware gets wet, dry it with a paper towel. Weigh the filled graduated cylinder and record the mass in your data table.

3. Obtain a dry rock sample and record the number on the rock. Weigh the rock sample and record the mass in your data table.

4. Pour an easily measured volume of water into a 250 mL graduated cylinder and record the exact volume in your data table.

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. Record the new volume of the water.

6. Obtain a wood block and record the number of the block. Weigh the wood block and record the mass in your data table.

7. Measure the length, width and height of the wood block and record the dimensions in your data table.

8. Place the wood block in a large beaker half–filled with water. Record what you see.

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 “cm3 ”. 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.

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