Answer the following question given this paragraph: 

In the last lesson, we studied the characteristics of liquids and solids at a macroscopic level and at the molecular level. Increasing the temperature of a solid transforms the particles from a rigid arrangement to a fluid (a liquid or gas). Conversely, decreasing the temperature of a liquid or gas slows the particles down, going back from free movement to a fixed arrangement. In this section, we will further explore how temperature and pressure affect the characteristics and behavior of matter. Pressure has a larger effect on gases, which are very compressible, than liquids and solids. However, changes in pressure are still relevant to solids and liquids. For example, Figure above shows ice skates on ice. Because your entire weight is all concentrated on a thin blade, ice skates exert quite a bit of pressure on the ice below them. An interesting property of water is that increasing the pressure on its solid form (ice) will eventually convert it to liquid water. The pressure exerted by ice skates makes small amounts of liquid water on the surface, allowing the skates to glide smoothly.


Q: What needs to be increased to change a solid into a liquid or gas?


A:
temperature