When a crystalline substance is heated, the average velocity of the molecules increases, which means the average kinetic energy and temperature, the range of vibrations of the molecules (or atoms) increases. When the melting point of the substance is reached, the arrangement of particles in the crystals is disrupted, the crystals lose their shape, the substance melts, passing from a solid to a liquid state.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.