Physical and Chemical Properties

The idea

A physical property can be observed without changing what the substance is. A chemical property describes how it behaves when it does change into something else.

Physical	Chemical
Colour, odour, texture	Flammability
Melting and boiling point	Reactivity with acid
Density	Ability to rust or tarnish
Solubility	Toxicity
Conductivity	Stability when heated

Density, because it comes up constantly

$$\rho =\frac{m}{V}$$

A block with a mass of $54.0\mathrm{g}$ and a volume of $20.0\mathrm{c}{\mathrm{m}}^3$:

$$\rho =\frac{54.0\mathrm{g}}{20.0\mathrm{c}{\mathrm{m}}^3}=2.70g/c{\mathrm{m}}^3$$

That is aluminium. Density is a characteristic physical property: it identifies a substance regardless of how much you have.

Why does size not matter?

Cut the block in half and both mass and volume halve. Their ratio does not move. Properties that behave this way are far more useful for identification than ones that depend on sample size.

Curriculum connection

C2.6

investigate and describe physical and chemical properties of elements and compounds, including those that make up common household products

Link to original

C2.1

investigate properties, changes, and interactions of matter that are important for the dynamic equilibrium of ecosystems and their sustainability

Link to original