# Physical Properties of Elements

## Basics on Physical Properties

• Physical properties are characteristics that can be observed or measured without changing the composition of the substance.
• These properties include colour, smell, freezing point, boiling point, melting point, opacity, viscosity and density.

## Density

• Density is a physical property of matter defined as mass per unit volume.
• It can be measured through the formula density = mass/volume, typically in units of g/cm^3 or kg/m^3.

## Viscosity

• Viscosity is a measure of a fluid’s resistance to flow. It’s often described as the material’s ‘stickiness’ or ‘thickness’.
• For example, honey has a higher viscosity than water because it flows more slowly.

## Boiling and Freezing Points

• Boiling point is the temperature at which a substance changes from liquid to gas, whereas freezing point is the temperature at which a substance changes from liquid to solid.
• Different elements have different boiling and freezing points; for instance, the boiling point of water is 100°C and its freezing point is 0°C at standard atmospheric pressure.

## Opacity

• Opacity is a measure of how much light a material absorbs or reflects.
• Transparent materials let most light through, opaque materials do not let light through, and translucent materials let some light through but scatter much of it.

## Understanding of Physical Properties is Key

• Physical properties are generally used to observe and describe matter and can be used to classify different elements.
• They are also used to predict how substances will behave under certain conditions - for example, whether a substance will melt under certain temperatures.

Practice calculations involving density and common changes in state such as melting and boiling until you feel comfortable. Experiment with different substances to better understand the concept of viscosity and opacity. Talk with classmates or a teacher if you’re struggling to understand any of these properties - a different explanation or perspective can sometimes make all the difference!