Monday, Nov. 18th: “A” Day Tuesday, Nov. 19th: “B” Day Agenda Ch. 10 Tests Start Chapter 11: “States of Matter and Intermolecular Forces” Sec. 11.1: “States and State Changes” Penny/Water Activity Homework: Sec. 11.1 review, pg. 384: #1-7 Concept Review: “States and State Changes” *Quiz over section 11.1 next time*

Ch. 10 Tests “Causes of Change” Class Average Score (out of 60) Percentage 3A 53.19 88.65% 4B 52.23 87.05%

States of Matter Most substances can be in 3 states: Solid Liquid Gas

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.

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.

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.

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 both adhesion and cohesion will pull water up a narrow glass tube, called a capillary tube.

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. (why water forms drops)

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.

Changing States Most substances can undergo six changes of state: freezing melting evaporation condensation sublimation deposition

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.

Changes of State

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.

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.

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.

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.

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 (CO2)

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.

Penny/Water Activity The purpose of this activity is to demonstrate both cohesion and surface tension by seeing how many drops of water the surface of a penny can hold before water begins to spill over the edge. First, make a prediction (hypothesis): How many drops of water do you think you can get to stay on the surface of a penny?

Penny/Water Activity Next, get a penny, rinse it off using water and dry it thoroughly with a paper towel. Using a plastic dropper pipette, add water drop-wise, until the water begins to spill over the edge. Repeat, drying the penny off in-between trials, for a total of 3 trials. Find the average number of drops for all 3 trials. How many drops did you average? Was your prediction correct?

Penny/Water Activity Data Table Prediction (Hypothesis): How many drops of water do you think you can get to stay on the surface of a penny? ____________ Was your prediction correct? ________ Explain what you think was happening: Trial #1 Trial #2 Trial #3 Average

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