6.2 - Physical properties of alkali metals
Alkali metals are soft and melt at relatively low temperatures. Learn what these two physical properties mean and why a low melting point does not necessarily mean a liquid at room temperature.
Soft metals
Lithium, sodium and potassium are alkali metals. Unlike many familiar metals, they are soft: a suitable knife can cut them easily. Cutting changes a piece’s shape without making a new substance, so softness is a physical property.
Softness does not mean that these reactive metals are safe to touch. Any cutting demonstration is carried out by a teacher using suitable handling equipment.
Relatively low melting points
The melting point is the temperature at which a solid changes into a liquid. Alkali metals have relatively low melting points: they melt at lower temperatures than many other metals.
“Relatively” identifies a comparison, rather than saying that the melting point is below room temperature. Lithium, sodium and potassium are solids at ordinary room temperature because the room is still colder than their melting points.
Continue this lesson.
You’re previewing NovaLearn without an account. Create a free account to read the rest.
Create free account