Properties of Materials

Core concept

For example, diamond is one of the hardest natural materials, while cotton is soft; metals like gold and silver have high lustre, while wood does not. Salt and sugar dissolve easily in water (soluble), while sand does not (insoluble). A material's density determines whether it floats or sinks — wood generally floats because it is less dense than water, while iron sinks because it is denser. These properties are tested through simple experiments in the classroom, like the scratch test for hardness or dropping objects in water to test floating.