Is malleability a chemical or physical property?
Malleability is a physical property because it can be observed without a change in composition of a substance. Chemical properties are those which are observed during a chemical reaction, for example the tendency of iron to rust and form iron oxide, a new substance.
Malleability is a typical property of metals. It's the ability to be shaped or flattened by compressive stress, such as hammering or rolling. In metallic bonding the valence electrons are free to move around. This allows atoms to change position under stress without fracturing the material. This shifting of position of atoms relative to other atoms doesn't produce a different substance.
A roll of aluminum foil is an example of the malleability of metals. Gold is the most malleable metals, with the ability to be flattened into extremely thin sheets.
Malleability is a physical property of matter; it is not a chemical property of matter. It describes a piece of matter's ability to be molded into thin sheets. This could be done by either pounding it thinner by using something like a hammer, or pressing it thinner through rollers for example. It is a physical property, because malleability does not describe an ability to change into something else. It simply describes the ability to change shape. Whether a lump of steel stays a lump or gets rolled or pounded into thin sheets, the material is still steel. Other physical properties of matter are things like ductility (ability to be drawn into thin wires), density, color, smell, thermal conductivity, and freezing point.