(POM) Physical Properties Lesson

Physical Properties

Physical properties of matter are properties that can be measured or observed without matter changing to a different substance. For example, whether a given substance normally exists as a solid, liquid, or gas is a physical property. Consider water. It is a liquid at room temperature, but if it freezes and changes to ice, it is still water. Generally, physical properties are things you can see, hear, smell, or feel with your senses.

Physical properties include the state of matter and its color and odor. For example, oxygen is a colorless, odorless gas. Chlorine is a greenish gas with a strong, sharp odor. Other physical properties include hardness, freezing and boiling points, the ability to dissolve in other substances, and the ability to conduct heat or electricity. These properties are demonstrated in the picture below.

Physical Properties description Links to an external site.

Other examples of physical properties could include the following:

• Can it create a magnetic field or not?
• The type of material such as brittle, malleable, or ductile.   Brittle materials break easily (plastic). Materials that are malleable can be easily formed into different shapes (clay, dough). Ductile materials can be formed into long wires (copper).
• How dense the material is. Density is the mass per unit volume. Examples of dense materials include concrete and stones.

Density

Since density is an important physical property of matter, let's take a closer look at this property. It reflects how closely packed the particles of matter are. Density is calculated from the amount of mass in a given volume of matter, using the formula:

Density (D) = $\frac{\text{Mass (M)}}{\text{Volume (V)}}$

To better understand density, think about a bowling ball and a volleyball. The bowling ball feels heavy. It is solid all the way through. It contains a lot of tightly packed particles of matter. In contrast, the volleyball feels light. It is full of air. It contains fewer, more widely spaced particles of matter. Both balls have about the same volume, but the bowling ball has a much greater mass. Its matter is denser.

It is important to note that the density of an object does not depend on its size or shape. This means that a steel cube has the same density as a steel nail or a steel girder for a bridge.  

Steel Density description Links to an external site.

In addition, another important fact to know is that one milliliter takes up the same amount of space as one cubic centimeter. Meaning that the units for density can be g/mL or g/cm³.  Liquid volumes are most commonly expressed in milliliters, while volumes of solids are usually expressed in cubic centimeters.

As you solve density problems, you will need to use the density equation. If you know the density of a substance, then you can also rearrange the equation to find the other missing variable (either mass or volume). To help you rearrange the equation to find the missing variable, you can use the triangle method as pictured below.

Density Problems Links to an external site.

Practice Problems

What is the density of a substance that has a mass of 20 g and a volume of 10 mL?

Practice Problem

Looking For: Density	Solution:   Density = m / v   Density = 20 g / 10 mL   D = 2.0 g/mL
Given: Mass = 20 g Volume = 10 mL
Equation: Density = m/v

What is the volume of a 525-gram block of lead?  The density of lead is 11.3 g/cm³.

Practice Problem

Looking For: Volume	Solution:   $v=\frac{m}{D}$   $v=\frac{525g}{11.3g/cm^3}$     v = 46.5 cm3
Given: Mass = 525 g Density = 11.3 g/cm3
Equation:

Now it is your turn to solve density problems. Solve the problems given below. Be sure to check your answers and the feedback given before moving forward.

Practice Problems

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