Chapter 3: States of Matter Section 3.1 Solids, Liquids, and Gases Section 3.3 Phase Changes

Section 3.1 Solids, Liquids, and Gases Describing the States of Matter Key Concept: Materials can be classified as solids, liquids, or gases based on whether their shapes and volumes are definite or variable Shape and volume are clues to how the particles within a material are arranged.

Section 3.1 Solids, Liquids, and Gases Kinetic Theory Under ordinary conditions, why are objects solid, liquid, and gas? Kinetic energy-energy an object has due to its motion (**The faster an object moves, the more kinetic energy it has.) Key Concept: The kinetic theory of matter says that all particles of matter are in constant motion.

Section 3.1 Solids, Liquids, and Gases Def.-the state of matter in which materials have a definite shape and a definite volume Definite-the shape and the volume of the object won’t change (does not mean they can never change) **Almost all solids have some type of orderly arrangement of particles at the atomic level.

Section 3.1 Solids, Liquids, and Gases Have definite (or fixed) shape and volume The particles in a solid are held fairly rigidly in place.

Section 3.1 Solids, Liquids, and Gases Explaining the Behavior of Solids Key Concept: Solids have a definite volume and shape because particles in a solid vibrate around fixed locations. **Strong attractions among atoms restrict their motion and keep each atom in a fixed location relative to its neighbors. Atoms vibrate around their locations but do not exchange places with neighboring atoms.

Section 3.1 Solids, Liquids, and Gases Def.-the state of matter in which a material has a definite volume but not a definite shape The arrangement of atoms is more random.

Section 3.1 Solids, Liquids, and Gases Have a definite volume but no fixed shape. The particles in a liquid are free to flow around each other

Section 3.1 Solids, Liquids, and Gases Explaining the Behavior of Liquids Liquid particles have kinetic energy. Particles in a liquid are more closely packed than gas particles A liquid takes the shape of its container because particles in a liquid can flow to new locations. Particles’ attractions do affect their movement. (moving through a crowd of people)

Section 3.1 Solids, Liquids, and Gases Def.-the state of matter in which a material has neither a definite shape nor a definite volume **A gas takes the shape and volume of its container.

Section 3.1 Solids, Liquids, and Gases Have neither definite or fixed shape or volume. The particles in a gas are: widely disbursed, interact weakly, move independently at high speed, and completely fill any container they occupy.

Section 3.1 Solids, Liquids, and Gases Explaining the Behavior of Gases: Motion in Gases Particles in a gas are never at rest. Some particles move faster or slower than avg. speed of gas particles Particles can collide with container walls or each other causing one atom to slow down (lose kinetic energy) or speed up (gain kinetic energy). The constant motion of particles in a gas allows a gas to fill a container of any shape or size.

Section 3.1 Solids, Liquids, and Gases Other States of Matter Most matter is solid, liquid, or gas. 99% of all matter observed in the universe exists in a state not common to Earth Extremely high temps (sun, stars); matter exists as plasma Gases whose particles are so hot they have acquired an electrical charge.

Characteristics of Phase Changes Section 3.3 Phase Changes Characteristics of Phase Changes What happens when a substance changes from one state to another? Phase- when at least (2) states of the same substance are present, what each different state is called Ex. Iceberg (solid) in the ocean (liquid)

Characteristics of Phase Changes Section 3.3 Phase Changes Characteristics of Phase Changes Phase change-the reversible physical change that occurs when a substance changes from one state to another Key Concept: Melting, freezing, vaporization, condensation, sublimation, and deposition are six common phase changes.

Temperature and Phase Changes Section 3.3 Phase Changes Temperature and Phase Changes Measuring the temp. of a substance as it is heated or cooled is one way to recognize a phase change. Key Concept: ********The temperature of a substance does not change during a phase change.

Energy and Phase Changes Section 3.3 Phase Changes Energy and Phase Changes Key Concept: Energy is either absorbed or released during a phase change. Endothermic change -the system absorbs energy from its surroundings The amt. of energy absorbed depends on the substance. **Heat of fusion (melting)-the amount of energy absorbed for water (ice) to melt

Energy and Phase Changes Section 3.3 Phase Changes Energy and Phase Changes Ex. 1g of ice absorbs 334 joules (J) of energy as it melts; 1g of water releases 334 J of energy as it freezes Exothermic change-the system releases energy to its surroundings (freezing)

Section 3.3 Phase Changes Melting and Freezing Key Concept: The arrangement of molecules in water becomes less orderly as water melts and more orderly as water freezes. Melting-some molecules of water gain enough energy to overcome the attractions and move from their fixed positions When all molecules have enough energy to move, melting is complete.

Section 3.3 Phase Changes Melting and Freezing Freezing-the avg. kinetic energy of water molecules decreases (they move more slowly) Some molecules move slow enough for the attraction b/t molecules to have an effect When all the molecules are drawn into an orderly arrangement, freezing is complete.

Vaporization and Condensation Section 3.3 Phase Changes Vaporization and Condensation Vaporization-the phase change in which a substance changes from liquid into a gas Is an endothermic process 1g of water gains 2261J of energy when vaporized (amt. of energy called heat of vaporization) 2 Vaporization processes: evaporation and boiling

Section 3.3 Phases Changes Vaporization and Condensation Key Concept: Evaporation takes place at the surface of a liquid and occurs at temperatures below the boiling point. Evaporation-the process that changes a substance from a liquid to a gas at temps. below the substance’s boiling point. Molecules near the surface move fast enough to escape the liquid (water vapor/open container)

Vaporization and Condensation Section 3.3 Phase Changes Vaporization and Condensation In a closed container- water vapor collects above the liquid Vapor pressure-pressure caused by the collisions of the vapor with the container’s walls (vapor press. ↑ as temp ↑) Boiling-when vapor pressure=the atmospheric pressure (i.e.. The temp. that this occurs at is the boiling point.)

Vaporization and Condensation Section 3.3 Phase Changes Vaporization and Condensation Boiling- temp. goes up; molecules speed up; (100oC) molecules below the surface have enough kinetic energy to overcome the attraction of neighboring molecules Boiling point depends upon atmospheric pressure. High elevation=atmospheric pressure is lower; water can boil at temperatures lower than 100oC (takes food longer to cook)

Vaporization and Condensation Section 3.3 Phase Changes Vaporization and Condensation Condensation- the phase change in which a substance changes from a gas or vapor to a liquid Is an exothermic process Ex. Dew on grass

Sublimation and Deposition Section 3.3 Phase Changes Sublimation and Deposition Sublimation- phase change in which a substance changes from a solid to a gas or vapor without changing to a liquid first Is an endothermic process Ex. Dry ice; cold CO2 vapor causes water vapor in the air to condense and form clouds

Sublimation and Deposition Section 3.3 Phase Changes Sublimation and Deposition Deposition- when a gas or vapor changes directly into a solid without changing into a liquid first Is an exothermic process and the reverse of sublimation Ex. Frost on windows; water vapor in air makes contact w/ cold glass; it loses enough kinetic energy to change from gas to solid

Section 3.3 Phase Changes Endothermic Phase Changes (energy is absorbed; state of matter goes from more orderly to less orderly arrangement of particles) Melting Vaporization Sublimation

Section 3.3 Phase Changes Exothermic Phase Changes (energy is released; states of matter go from less orderly to more orderly arrangement of particles) Freezing Condensation Deposition

Figure 16 Phase Changes