Unit 3: States of Matter, Heat and Gas Laws

Transcription

1 Unit 3 - Stevens 1 Unit 3: States of Matter, Heat and Gas Laws Vocabulary: Solid Term Definition Example Liquid Gas No definite shape, but definite volume; Particles close together, but can move around freely/slide past each other; moderately attracted to each other; higher energy Plasma Phase change (Physical change of state from one form to another) Thermal energy Evaporation: liquid to gas Freezing: liquid to solid Melting: solid to liquid Condensation: gas to liquid Deposition: gas directly to solid Sublimation: solid directly to ice Evaporation: Freezing: Melting: Condensation: Deposition: water vapor directly to ice Sublimation: Kinetic Molecular Theory (KMT) Exothermic

2 Unit 3 - Stevens 2 Endothermic Conduction Convection Radiation Pressure Charles Law Boyle s Law Gay Lussac s Law pressure times the volume is a constant, for a given mass in a closed system, as long as the temperature is constant Avogadro s Law Equal volumes of gases, at the same temperature and pressure, contain the same number of particles, or molecules Section 1: States of Matter and Phase Changes Key Ideas 1. What is the difference between solid, liquid, gas and plasma? 2. What kind of energy do all particles of matter have? 3. What happens when a substance changes from one state of matter to another? Vocab: Solid plasma phase change

3 Unit 3 - Stevens 3 Liquid thermal energy Gas kinetic theory Kinetic Molecular Theory (KMT): There are 4 states of matter: There are four parts that make up the KMT: The higher the temperature of the substance, the faster the particles move (more kinetic energy) At the same temp, more massive particles move slower than less massive ones. These particles are colliding with each other and the walls of their container. Solid Particles: Definite shape and volume Draw the picture. Example: Liquid Particles: Draw the picture Example: Gas Particles: Draw the picture Example: Plasma Very high KE; particles collide with enough energy to break into charged particles (+ / ) Gas like, indefinite shape & volume This form is not too common on Earth, however it is the most common form of matter in the universe makes up ~99% of the universe!!! Examples: stars, florescent and neon lights, lightning Energy s Role: Energy is Energy of motion is called Kinetic Energy (KE). Since all particles (atoms) are moving, they all have KE. Most matter expands when heated & contracts when cooled. Why? The more energy, the higher the temperature. Particles collide with more force & spread out. more energy means more movement for the particles and less energy means less movement. So which state of matter has the least energy? If you were to compare an ice cube and the steam created from boiling water, which would you think

4 Unit 3 - Stevens 4 has more energy and WHY? Thermal Energy: Thermal Energy: o Depends on Example: temp is not determined by how much of a substance you have, a teapot and freshly poured mug of tea is the same temp However, the thermal energy in each container is different, because the number of particles is different States of Matter Continuum: Draw Diagram: Energy and Changes of State Phase Change: Law of conservation of mass and energy: The identity and mass of a substance does not change during a change of state As heat (energy) increases, the state of matter changes. Solids go to liquids, liquids to gases and so on. This is called a phase change. A phase change is a physical change. Some examples are: These phase changes can also happen when heat (energy) is lost. Endothermic vs Exothermic For some phase changes, Condensation Freezing Deposition Sublimation Melting

5 Unit 3 - Stevens 5 Vaporization Fill in table: Change of State Phase Change Energy added or lost? Examples Practice: 1. If you pour an object from one container to another and it loses volume, do you have a solid, liquid, or gas? 2. Do particles slow down or speed up during the following phase changes? a. Freezing b. Boiling c. Sublimation d. Melting 3. What does temperature measure? 4. Create phase change diagrams on separate sheet of paper. Section 2 Heat Key Ideas: How does heat energy transfer happen? What is heat The Nature of Heat Under normal conditions and in nature,

6 Unit 3 - Stevens 6 Heat energy will flow from one substance to another until the two substances have the same temperature How is heat transferred? What is heat? Heat can be transferred 3 ways: Conduction Convection Radiation Conduction Radiation Convection Conduction: The transfer of heat from one particle of matter to another by direct particle to particle contact. The particles themselves DO NOT change positions. Can you think of an example of conduction? Conduction section (from Ex: If you have ever left a silver spoon in very hot soup, you will notice that the whole spoon gets hot. Thermal energy is transferred from the hot end of the spoon through the entire length of the spoon. This is called conduction.

7 Unit 3 - Stevens 7 Particles often collide with each other. When this happens, energy is transferred from the faster (hotter) moving particle to the slower (cooler) moving particle. This makes the slower moving particles increase in speed. When molecules in a substance are made to move faster, they get warmer. The warmer an object gets, the more kinetic energy and therefore, thermal energy it contains. In solids (especially metals), electrons in atoms collide with each other inside the object being heated.. The rate at which the kinetic or thermal energy is transferred from one particle to another depends on the separation of the particles and their freedom to move. In a gas, the particles are allowed to move freely, but their separation distance is great, In a liquid, the heat transfer by conduction is because the particles are closer together. In a solid, the molecules are constrained into a specific location within the material, which can make for quick conduction. Although the particles are closer together than in liquids, the constraints in some materials actually prevent the transfer of heat energy. A good example of that is in wood. Brainstorming: What are other examples of conduction? Application: Describe the process of conduction when you place a hot spoon into a bowl of ice cream. Convection: Convection: Convection produces in both gases and liquids. Thermal Energy heat is carried by the particles as they move from one location to another. Example: Heating water: a. When the water at the bottom of the pot (nearest the burner) is heated, the particles absorb energy by conduction as they touch the hot pot.

8 Unit 3 - Stevens 8 b. The water particles vibrate more rapidly. c. The particles also move farther apart and the hot water becomes less dense than the surrounding cool water. d. This causes the heated (hot) water to rise. e. The surrounding denser cooler water is forced downward near the burner by the rising hot water. f. This process continues to repeat. g. This FLOW creates a circular motion known as a convection current. Application: 1. How do convection currents form in a room when the heater is turned on? 2. What is the best location for a heat vent in a room and why? Near the ceiling or the floor? Convection currents occur in the environment as well. They produce: Ocean and lake currents Brainstorming: On a hot summer day the breeze near the beach blows toward the water. However, later in the day the breeze reverses direction and blows toward land and will get increasingly stronger. Why? Radiation: Radiation: the transfer of (thermal) energy by electromagnetic waves. All the sun s energy that reaches Earth travels through millions of kilometers of empty space (a vacuum). You feel the radiation of thermal energy from a bonfire, a heat lamp and a light bulb. You don t need to touch it! Other examples of the transfer of heat by Radiation: Charcoal grill. Hot tin roof. Burner on a stove top. Key Point: For radiation to be felt as heat it must first be absorbed by a material.

9 Unit 3 - Stevens 9 Example: Why do blue jeans feel hotter in the sun than a yellow shirt, even though they are both exposed to the same amount of sunlight? Section 3 Pressure and Gas Laws Key Ideas What causes pressure? What are some properties of gases? How can you predict the effects of pressure, temperature, and volume changes on gases? What is pressure? Pressure = Force / Area, P=F/A Measured in the SI unit pascal Example: pumping up a bike tire What do you think is happening with the molecules when you add air? Properties of Gases: They spread out easily and mix with one another They have low densities and are compressible Gases exert on their containers, through SEGMENT 1 QUESTIONS: What do you think pressure is? Use the video to answer the following questions: What causes pressure? What causes higher pressure?

10 Unit 3 - Stevens 10 SEGMENT 2 QUESTIONS: 1. Why does the balloon deflate? 2. Draw the balloon and indicate the pressure differences. 3. Why does a balloon stay blown up? 4. What do you think would happen if we put a balloon in the hot sun? Why? SEGMENT 3 QUESTION: Describe how pressure works, using air molecules as an example. SEGMENT 4 and 5 QUESTIONS: 1. Why do you think the marshmallow peeps expand when air is sucked out? 2. Why do they get smaller when air is put back in? 3. What s happening with the regular marshmallows? Gas Laws: How do you measure the volume of a gas? Gases behave differently than liquids and solids. The gas laws mathematically describe how the behavior of gases is affected. Gas laws help us understand and predict the behavior of gases in specific situations. Ideal Gas Law: P 1 V 1 = P 2 V 2 T 1 T 2

11 Unit 3 - Stevens 11 General law that describes how gases will behave when one variable is held constant. More specific laws are Boyle s Law, Gay Lussac s Law, and Charles s Law Boyle s Law (constant temperature): What is Boyle s Law? PV=k (pressure times the volume is a constant, for a given mass in a closed system, as long as the temperature is constant) To compare the same substance under two sets of conditions, we use the formula: Pressure 1 * Volume 1 =Pressure 2 *Volume 2 or P 1 V 1 =P 2 V 2 For a fixed amount of gas at a constant temperature, the volume of a gas increases as the gas s pressure decreases. Likewise, the volume of a gas decreases as the pressure increases. Write Boyle s law in two If X happens, then Y happens statements. What two conditions have to be true to make this happen? Boyle s Law Practice Problem: The gas in a balloon has a volume of 7.5L at 100.0kPa. In the atmosphere, the gas expands to a volume of 11L. Assuming a constant temperature, what is the final pressure in the balloon? Given: V 1 =7.5L Unknown: P 2 =??? P 1 =100.0kPa V 2 =11L Write equation and solve for P 2. Equation: P 1 V 1 =P 2 V 2 P 2 = P 1 V 1 / V 2 P 2 = (100.0kPa)(7.5L) / 11L P 2 = 68kPa You try: If the pressure exerted on a 300 ml sample of hydrogen gas at constant temperature is increased from.500kpa to.750kpa, what will be the final volume of the sample? Gay Lussac s Law (constant volume of gas): The pressure of a gas increases as the temperature increases, if the volume of the gas does not change. The pressure decreases as the temperature decreases. Example: The tire pressure of your bike is lower in winter than it is in summer. This is because as the temperature outside decreases, so does the pressure in your tire and vice versa. No new air molecules are added.

12 Unit 3 - Stevens 12 Charles Law (constant pressure): For a fixed amount of gas at a constant pressure, the volume of the gas increases as the gas s temperature increases. Likewise, the volume of the gas decreases as the gas s temperature decreases. Example: an inflated balloon will pop when it gets too hot, or will shrink when it gets too cold. Avogadro s Law: Practice: 1. Which law does this graph show? 2. What are four properties of gases? o o o o 3. Which law does this graph show? 4. Does the above graph show an indirect or direct relationship? 5. Give an example for each ideal gas law. o Charles Law

13 Unit 3 - Stevens 13 o o Boyle s Law Gay Lussac s Law