2. Tuesday, Nov. 27 th : “A” Day Wednesday, Nov. 28 th : “B” Day (1:05 dismissal) Agenda  Ch. 10 Tests  Start Chapter 11: “States of Matter and Intermolecular Forces”  Sec. 11.1: “States and State Changes”  In-Class: pg. 384, #1-7  Homework: Concept Review: “States and State Changes” *Quiz over section 11.1 next time*

3. Ch. 10 Tests “Causes of Change” Class Average Score Percentage 2A49.6882.80% 4B52.0086.67%

4. States of Matter  Most substances can be in 3 states: –Solid –Liquid –Gas

5. Mercury in 3 States  Hg is the only metal that is a liquid at room temperature.  When cooled below -40°C, Hg freezes to a solid.  When heated to 357°C, Hg boils and becomes a gas.

6. Solids  The particles in a solid are very close together and have an orderly, fixed arrangement.  Solid particles can vibrate only in place and do not break away from their fixed positions.  Solids have fixed volumes and fixed shapes.  Solids can be hard and crystalline, like NaCl or soft like Pb.

7. Liquids  The particles in a liquid are very close together and have a random arrangement.  Liquid particles have enough energy to be able to move past each other readily, which allows liquids to flow.  Some liquids flow easily, like water. Other liquids, like molasses, flow more slowly because they are viscous.  Liquids have fixed volumes but can flow to take the shape of the lower part of a container.

8. Surface Wetting and Capillary Action  Liquid particles can have cohesion, attraction for each other. (Group Hug!)  Liquid particles can also have adhesion, attraction for particles of solid surfaces.  The balance of cohesion and adhesion determines whether a liquid will wet a solid surface.  The forces of adhesion and cohesion will pull water up a narrow glass tube, called a capillary tube.

9. Surface Tension  Below the surface of a liquid, the particles are pulled equally in all directions by cohesive forces.  However, surface particles are pulled only sideways and downward, so they have a net downward force.  It takes energy to oppose this net force and increase the surface area.  Surface tension: the force that acts on the surface of a liquid and that tends to minimize the area of the surface.

10. Gas Particles are Essentially Independent  The particles in a gas are very far apart and have a random arrangement.  The attractive forces between particles in a gas do not have a great effect, so the particles move almost independently of one another.  The shape, volume, and density of an amount of gas change depending on the size and shape of the container.  Gases are considered fluids because they can flow easily.

11. Changing States Most substances can undergo six changes of state: 1.freezing 2.melting 3.evaporation 4.condensation 5.sublimation 6.deposition

12. Temperature, Energy, and State  Generally, adding energy to a substance will increase the substance’s temperature.  But after a certain point, adding more energy will cause a substance to experience a change of state instead of a temperature increase.

13. Changes of State

14. Liquid Evaporates into a Gas  Energy is required to separate liquid particles. They gain energy when they collide with each other.  If a particle gains a large amount of energy, it can leave the liquid’s surface and join gas particles.  Evaporation: the change of a substance from a liquid to a gas. Evaporation is an endothermic process because energy is absorbed.  Boiling point: the temperature and pressure at which a liquid and a gas are in equilibrium.

15. Gas Condenses to a Liquid  When gas particles no longer have enough energy to overcome the attractive forces between them, they go into the liquid state.  Condensation: the change of state from a gas to a liquid. Condensation is an exothermic process because energy is released.  Example: Condensation can take place on a cool night, causing water vapor in the air to form dew on plants.

16. Solid Melts to Liquid  As a solid is heated, the particles vibrate faster and faster in their fixed positions.  At a certain temperature, some of the molecules have enough energy to break out of their fixed positions.  Melting: the change of state in which a solid becomes a liquid by adding heat or changing pressure. Melting is an endothermic process.  Melting point: the temperature and pressure at which a solid becomes a liquid.

17. Liquid Freezes to Solid  As a liquid is cooled, the movement of particles becomes slower and slower.  At a certain temperature, the particles are pulled together into the fixed positions of the solid state.  Freezing: the change of state in which a liquid becomes a solid as heat is removed. Freezing is an exothermic process.  Freezing point: the temperature at which a liquid substance freezes.

18. Solid Sublimes to Gas  The particles in a solid are constantly vibrating. Some particles have higher energy than others.  Particles with high enough energy can escape from the solid.  Sublimation: the process in which a solid changes directly into a gas. Sublimation is an endothermic process.  Examples: napthalene in mothballs, dry ice (CO 2 )

19. Gas Deposits to Solid  Molecules in the gaseous state become part of the surface of a crystal.  When a substance changes state from a gas to a solid, the change is often called deposition. Deposition is an exothermic process.  Example: frost forms on exposed surfaces during a cold night.

20. In-class assignment  Section 11.1 review Pg. 384: #1-7  Homework: Concept Review: “State and State Changes” * Quiz over this section next time*