Gallium is an interesting metal in that it has a relatively low melting point of about 29.76 °C (85.57 °F), which is just above room temperature. When gallium is heated to its melting point, the following changes occur at the molecular level:
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Phase Transition: As gallium warms up and reaches its melting point, it transitions from a solid to a liquid state. In the solid state, the atoms are arranged in a structured lattice, with fixed positions, and they vibrate around those positions. In the liquid state, the atomic arrangement becomes more disordered.
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Molecular Movement: In the solid form, gallium atoms are held together by metallic bonds and are not free to move around significantly. As it melts, these bonds weaken due to the increased kinetic energy from the heat, allowing atoms to move more freely. This results in a liquid that can flow and take the shape of its container.
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Thermal Energy: Upon reaching the melting point, additional thermal energy (heat) provides the energy needed to break the interactions holding the atoms in the solid lattice. However, the temperature of the substance doesn't increase significantly during this phase change (this is known as the latent heat of fusion) until the transformation to liquid is complete.
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Density Change: Gallium also has the unique property of expanding upon freezing, which is uncommon for metals. When gallium solidifies, its volume increases, leading to a decrease in density. This is why gallium can actually float on its own liquid when it is solid.
In summary, during the melting of gallium, its atomic structure transitions from a solid, ordered arrangement to a disordered, flowing liquid state, facilitated by the absorption of thermal energy, which allows the atoms to move more freely.