17%(6)1 out of 6 people found this document helpful
This preview shows page 1 - 2 out of 3 pages.
Name ___________________________________________ Date ______________________ Class ________________________ To study the phase changes as water is heated from solid to liquid to water vapor. Melting, boiling, freezing, condensation: these are all things you have experienced in your daily life. You have seen water change phases over and over again, but have you ever taken time to think about why it happens? Did you know that phase changes either absorb energy or release energy? Vaporization Depending on the temperature, most substances can exist as both a solid and a liquid. A substance in its liquid state has more thermal energy than it has in its solid state. The temperature at which the transition from a solid to a liquid takes place is the melting point of the substance. The molecules that make up a gas have more thermal energy than molecules of the same substance in the liquid state. The liquid molecules are in close contact with each other while gas particles are spaced significantly further apart. The transition from a liquid to a gas is known as vaporization and occurs by either evaporation or boiling. The normal boiling point is the temperature at which the substance boils at sea level. Melting and vaporization points are characteristic properties of a substance. Chemists often use these points to help identify or classify a substance.