As a materials science expert with extensive knowledge in the behavior of materials, particularly metals, I can provide a comprehensive explanation of what happens when metal is heated.

When metal is subjected to heat, a phenomenon known as thermal expansion occurs. This is a fundamental property of all materials, but it is especially noticeable in metals due to their crystalline structure. The atoms in a metal are arranged in a regular, repeating pattern, known as a crystal lattice. At normal temperatures, these atoms vibrate about their fixed positions within the lattice, but they are held in place by strong metallic bonds.

As the temperature increases, the kinetic energy of the atoms also increases. This additional energy causes the atoms to vibrate more vigorously. The increased vibrations lead to a greater average distance between the atoms. Since the atoms are no longer held as closely together, the metal expands. This expansion affects the length, surface area, and volume of the metal. The extent of this expansion varies depending on the type of metal; some metals expand more than others when heated.

The process of thermal expansion is described by the formula:

\[ \Delta L = \alpha \cdot L_0 \cdot \Delta T \]

Where:
- \( \Delta L \) is the change in length,
- \( \alpha \) is the coefficient of linear expansion,
- \( L_0 \) is the initial length,
- \( \Delta T \) is the change in temperature.

This formula shows that the amount of expansion is proportional to the initial length of the material and the change in temperature. The coefficient of linear expansion (\( \alpha \)) is a material-specific constant that indicates how much a material expands per degree Celsius (or per degree Fahrenheit).

Thermal expansion has several practical implications. In engineering and construction, it is crucial to consider the expansion and contraction of materials due to temperature changes to prevent structural failure. For example, bridges and roads are designed with expansion joints to accommodate this expansion without causing cracks or other damage.

Another important aspect of heating metals is the change in mechanical properties. As metals are heated, they can become softer and more ductile, which can be advantageous for processes like forging and rolling, where the metal needs to be shaped. However, if heated too much, metals can lose their strength and become more susceptible to deformation or failure.

Additionally, the heating of metals can also lead to phase transformations. For instance, some metals may undergo an allotropic transformation, changing their crystal structure at certain temperatures. This can significantly affect the metal's properties, such as hardness, electrical conductivity, and magnetic properties.

In summary, when metal is heated, it undergoes thermal expansion due to increased atomic vibrations, which increases its length, surface area, and volume. This phenomenon must be carefully managed in various applications to ensure the integrity and performance of metal components.

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Metal expands when heated. Length, surface area and volume will increase with temperature. The scientific term for this is thermal expansion. ... Thermal expansion occurs because heat increases the vibrations of the atoms in the metal.Sep 9, 2015read more >>