Engineers know what materials to use for a specific job, or the type of material they need for a job, because they carefully study the properties of different materials. In other words they study how a material performs under certain conditions. There are a number of different material properties. Physical properties are measures of a material s size, density, porosity and surface texture.
Mechanical properties are measures of how a material reacts to mechanical forces.
Finally, mechanical properties describe how elastic or plastic a material is. Elastic materials are those like elastic bands which can be stretched but return to their original shape. Plastic materials are those like clay which can be molded or pushed into shape. A spring Wet sand Bubble gum Cement Mud Thermal properties tell engineers how a material reacts to hot and cold. Some materials, like concrete, tend to expand in the heat and shrink in the cold.