5. A blacksmith strikes a piece of metal with a hammer repeatedly. The metal slowly begins to glow as the temperature increases, and the metal becomes more malleable. Which changes on a microscopic level led to the visible changes in the properties of the metal?
On a microscopic level, the repeated striking of the metal by the blacksmith's hammer causes several changes that ultimately lead to the visible changes in the properties of the metal, such as glowing and increased malleability.
1. Dislocation movement: When the blacksmith strikes the metal, the force applied causes dislocations in the metal's crystal lattice structure. Dislocations are defects or irregularities in the arrangement of atoms in a crystal structure. As the hammer strikes the metal, these dislocations move and rearrange, leading to plastic deformation.
2. Plastic deformation: Plastic deformation refers to the permanent change in shape or size of a material without fracture or failure. The repeated striking of the metal causes the dislocations to move, enabling the metal to undergo plastic deformation. This plastic deformation leads to a change in the arrangement of atoms within the metal, and the metal becomes more malleable or easier to shape.
3. Energy absorption: As the blacksmith strikes the metal, the repeated impacts transfer energy to the metal. This energy is converted into heat due to friction between the metal atoms. The increased temperature causes the metal to slowly start glowing as it reaches higher energy levels, ultimately leading to a visible change.
4. Recrystallization: The repeated plastic deformation and dislocation movement promote recrystallization within the metal. Recrystallization is a process where new strain-free grains or crystals are formed within the deformed metal. This process helps relieve the accumulated stress within the metal and improves its malleability.
In summary, the microscopic changes involved in the repeated striking of the metal by the blacksmith's hammer include dislocation movement, plastic deformation, energy absorption, and recrystallization. These changes collectively lead to the visible properties of the metal, including glowing and increased malleability.