The document discusses different changes of state that substances can undergo. It explains that changing from one state to another, such as solid to liquid, requires adding or removing energy. Melting occurs when a solid turns to a liquid, and freezing is the reverse change. Evaporation changes a liquid to a gas below the boiling point, while boiling occurs when a liquid turns to a gas throughout. Lower pressure lowers the boiling point of a substance, while higher pressure raises the boiling point. The document also mentions sublimation, which is when a solid turns directly to a gas.

1. Chapter 4 Changes of State

2. Warm-Up 10/14/10 Two pots of boiling water each cook an egg. One pot is at a high elevation. The other pot is at sea level. It takes one minute longer to hard-boil the egg at high elevation. Why? (Think pressure and temperature)

3. Energy and Changes of State A change of state is the change of a substance from one physical form to another. To change from one state to another you must add of remove energy (heat).

5. Melting / Freezing Freezing point – liquid changes into solid. Melting Point - solid changes into liquid. Same Temperature Water : 0º C

6. Evaporation/ Boiling Evaporation: liquid at the surface changes into gas Can happen below boiling point Boiling: liquid throughout changes into gas.

7. Pressure Pressure effects states of matter too: Less pressure = lower boiling point More pressure = higher boiling point

8. Boiling / Condensation Boiling : liquid to gas Condensation : gas to liquid Same temperature : Water 100º C

9. Sublimation When a substance goes directly from a solid to a gas. (Dry Ice)

10. Homework Section Review: Copy down the questions Page 119, # 1-7