INTRODUCTION

The physical properties of a pure substance are those that can be measured without changing the composition of the substance. The density of a substance is an intensive property of the substance. The property is independent of the mass of the substance ( intensive ). The density of a substance is a measure of the mass of the substance per volume occupied by the substance. In chemistry the density of solids and liquids are generally given in units of grams per milliliter, while for gases the units are grams per liter.

You will be determining the density of water, the density of an unknown liquid, the density of a regular solid and the density of an irregular solid.

EQUIPMENT

Top loading balance, analytical balance, 10 mL graduated cylinder, 25 or 50 mL graduated cylinder, 50 or 100 mL beaker, vernier calipers.

CHEMICALS

Deionized Water, an unknown liquid, a known metal cylinder, an unknown irregular metal.

PROCEDURE

Part I. Density of Deionized Water.

Half fill (by estimation) a 50 mL ( or 100 mL ) beaker with deionized water and weigh it on the analytical balance. Carefully transfer some of the deionized water to a dry graduated cylinder so that the volume is between 7 and 9 mL. Reweigh the beaker with the remaining water. Accurately measure the volume of water in the graduated cylinder.

The difference in the weights of the beaker of water before and after you have transferred the water is equal to the weight of water transferred. You now have the mass of water and the volume of that mass of water. You can calculate the density of the water.

Part II. Density of an Unknown Liquid.

On a top loading balance or an analytical balance weigh a clean, Dry, empty 10 mL graduated cylinder. Add the unknown liquid using a medicine dropper until the volume is between 7 and 9 mL. Reweigh the graduated cylinder with the unknown liquid. Accurately measure the volume of the unknown liquid present in the graduated cylinder.

The difference in weights of the graduated cylinder before and after the unknown liquid is added is the mass of the unknown liquid. You have the mass of the unknown liquid and its volume. You can calculate the density of the unknown liquid.

Part III. Density of a (cylindrical) Known Metal.

Obtain one of the known metal cylinders and weigh it on the analytical balance. Record both the masses of the cylinder and the metal you are using. Measure the diameter of the cylinder and the length of the metal cylinder using the calipers. Record the measurements to the nearest hundredth of a centimeter (± 0.01 cm ). Using the formula calculate the volume of the right cylinder. Volume = area of base (area of circle) x height.

Where r is the radius of the circular base of the cylinder , h is the height of the cylinder

And p = 3.14.

But the diameter, d , of the base (which is easier to measure) is equal to 2 x radius.

, or . Then squaring both sides will give you, , substituting this into the equation will give you,

.

Calculate the density.

Part IV. Density of an Unknown Irregular Metal.

Obtain a 50 mL (or 100 mL ) graduated cylinder. Add water to the cylinder and record the volume of water present in the graduated cylinder. Weigh the cylinder with the water. Remove from the balance and add small amounts of the unknown irregular metal until the level of water in the graduated cylinder has increased by at least 10 mL. Gently shake the graduated cylinder so that any air bubbles that are on the surface of the metal are shaken off. Record this new volume. Place the graduated cylinder back on the same balance and record the new weight. The difference in the two weighings gives you the mass of the metal and the difference between the two levels of water in the graduated cylinder gives you the volume of the metal. Calculate the density of the metal. Also remember to indicate which unknown metal you are using.