Comparison of the Properties of Two Objects

Purpose: The purpose of this lab is to distinguish properties of objects from properties of the substance from which the object is made.

As you are working in the laboratory in General Chemistry, you are going to be asked to make many observations of the properties of the substances with which you are working, and to record these observations as data on a laboratory report sheet. Some of these observations will be qualitative, such as color or physical state, but many will be quantitative, such as how much mass, how much volume, or what temperature. These measurements should be made as precisely as possible and must include both the magnitude and the units of measurement. This first exercise is to give you a chance to make a series of observations and comparisons of the properties of two metal slugs.

Theory: Some properties are of the substance itself as, for example, the color of silver is due to silver and not due to the size of the sample. Properties particular to the substance are referred to as intensive properties. Other properties of the sample may be due to the quantity of material present and not specific for that substance. For example the mass of an object is due to the quantity of the material in the sample and is not an inherent property of the substance. These properties are referred to as extensive properties. As you record your properties under the two columns, you should also indicate whether these are extensive properties or intensive properties.

(Starred items*)

Procedure:

Perform steps 1 to 4 for both a 10 mL and a 25 mL graduated cylinder.

1. Measure the mass of a dry graduated cylinder.

2. (a) Fill the cylinder with water and record the mass of the cylinder + water.

(b) Record the precise volume of water. Remember to use the limit of measurement

learned last week!

3. Calculate the mass of the water in the cylinder.

4. Calculate the density of water by dividing the mass of the water by the volume of water measured (density units are grams per mL). Calculate the average density of water and record this value in the last column.

5. Weigh the slugs and record the mass. Make sure you record your masses to a thousandth of a gram (0.001 g).

6. Measure the length and diameter of each slug as accurately as possible. Use the calipers for these measurements.


7. Calculate the volume of each slug using the following formula:

V = pr2h, or more specifically

8. Now, determine the volume of each slug by immersion in water. Read precisely the amount of water you have added. This is the initial reading 8.

9. Now add the slug. The water level should be above the slug. This is the final reading 9. If the water level is not above the slug, go back to step 8 and add more water.

10. Calculate the volume for each slug.

Volume = final reading - initial reading (units are mL)

11. The values for each slug in parts (7) and (10) should agree within 0.6 mL. If they do not, go back and check your measurements before calculating the average volume.

12. Calculate the density of each slug.

13. Calculate the specific gravity of each slug using the values determined
in parts (4) and (12).

14. Record the color of each slug.

15. Be sure to record the slug code for each slug used in this experiment.

16. Try to identify the chemical composition of each slug. The specific gravity of several metals and alloys are given below. Use the color of the slug and its specific gravity in identifying the composition.

Material / Specific gravity
Copper / 8.92
Stainless steel / 7.75
Aluminum / 2.70
Brass / 8.40


Comparison of the Properties of Two Objects DATA SHEET

Name ______Date ______Section______

Part I / 10.0 ml
graduated
cylinder / 25.0 ml
graduated cylinder / Intensive or
Extensive Property
1. Mass of empty graduated cylinder / *
2. (a) Mass of grad. cylinder + water
(b) Volume of water
3. Mass of water / *
4. Density of water
Average density of water / *
Part II / Slug A / Slug B / Intensive/Extensive
5. Mass of Metal Slug
(a) Length of Slug
(b) Diameter of Slug
7. Volume (Calculated)
8. Volume before adding Slug
9. Volume after adding Slug
10. Volume (by Displacement) / *
11. Average Volume
12. Density of Slug / *
13. Specific Gravity / *
14. Color of Slug
15. Slug Code
16. Identity of Unknown