When we describe properties of substances, we can divide them into chemical properties and physical properties. Chemical properties are how the substance react with other substances, while physical properties are mostly observable or measurable, which does not require the substance into reacting with other substances.
Since group I are all metals, the physical properties include shiny, malleable, ductile, good conductors of heat and electricity, have high melting points etc.
Chemical properties include react vigorously with water to form metal hydroxide and hydrogen, or react with oxygen to form metal oxide.