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Density is a characteristic property of a substance that can be used to identify substances. The density of a substance does not change no matter how much or how little of a sample that you have. Density is the mass contained in one unit volume of a substance. | ||||||||||||||||
The density of an object can be used to predict whether an object will sink or float in water. Water has a density of one gram per cubic centimeter. If an object has a density greater than 1 g/cm3, it will sink. If an object has a density less than 1 g/cm3, it will float. | ||||||||||||||||
In most cases, the density of an object can be used to predict whether it is a solid, liquid or a gas. Solids generally have a density greater than water. For example, aluminum has a density of 2.7 g/cm3. Yet, oak (0.75 g/cm3) is a solid and floats in water. Most liquids have a density near 1 g/cm3. An exception is mercury which has a density of 13.6 g/cm3. Gases have densities that are very small. For example,carbon dioxide has a density of 0.0018 g/cm3 | ||||||||||||||||
CALCULATION OF DENSITY: Density is the mathematical relationship between two properties common to all matter: mass and volume. The density of any sample of matter can be found by using the formula: | ||||||||||||||||
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MEASURING MASS: Mass is a measure of the amount of matter in an object. In a laboratory, mass is measured with a balance. The basic unit used for measuring mass is the gram. | ||||||||||||||||
MEASURING VOLUME: Volume is a measure of the amount of space an object takes up. The volume of a regularly shaped object can be calculated by measuring the length, width, and height (volume = length x width x height). These measurements are then multiplied together. The volume of an irregularly shaped object can be found by displacement of water using a graduated cylinder. Fill the graduated cylinder about half way with water, and record this volume. Then put the solid object gently into the cylinder. The level of water in the cylinder rises. Record the new volume. The difference between the two measurements is the volume of the solid. To find the difference, subtract the original volume of water from the new volume of water. The units of measurement on a graduated cylinder are milliliters (ml). | ||||||||||||||||
Volume of liquid and solid_________________ | ||||||||||||||||
Volume of liquid (subtract)_________________ | ||||||||||||||||
Volume of solid _________________ | ||||||||||||||||
Problems dealing with mass, volume and density can be solved using one of the following three relationships.
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