Ch. 2 “Matter” 2.1: “What Is Matter?” 2.2: “Matter and Energy” 2.3: “Properties of Matter”
2.2: “Matter & Energy” Objectives: Use the kinetic theory to describe the properties and structures of the different states of matter. Describe energy transfers involved in changes of state. Describe the laws of conservation of mass and conservation of energy, and explain how they apply to changes of state.
Recall Method: Why can you smell cookies baking in a bakery when you are far from the oven?
Reasons… 1st: Assume that particles (atoms & molecules) within substances can move. 2nd: Assume that the atoms & molecules move faster as the temperature rises. 3rd: Energy moves from the oven to the cookies, causing molecules in the cookie dough to move fast & become gases which spread out.
Kinetic Theory All matter is made of atoms & molecules that act like tiny particles. Tiny particles are in constant motion. Higher temp. faster the movement. At the same temperature, more massive (heavier) particles move slower than less massive (lighter) particles.
Fluids
Solids: Rigid structure Fixed volume and shape Strong attractions of particles = vibrate Liquids: Definite volume No specific shape Particles flow = easily slide Viscosity: The resistance of a fluid to flow. (The higher the attraction of the particles, the slower fluid will flow.) ** both liquids and gases are fluids!! Gases: Particles are far apart & move randomly No fixed volume or shape Gases can exert pressure
Why does a balloon with helium go “flat” faster than a balloon filled with air? The wall of the balloon has tiny holes through which gas particles can escape. The helium particles are smaller & less massive than the nitrogen & oxygen particles found in the air. The smaller & less massive particles move faster, so they get through the holes more quickly.
What is the role of energy? Demonstration (2 volunteers) 1) Dip one index finger into the water. Dip your other index finger into the oil. Wave each finger in the air. 2) Do your fingers feel cool? 3) Which liquid evaporated faster? 4) Repeat experiment using water on one finger and rubbing alcohol on the other.
What happened?? Which of the three liquids evaporated the fastest? Slowest? Which liquid cools the skin the most? Least? The molecules in each liquid absorb energy from their surroundings (skin) increasing the speed of molecules. Alcohol requires the least energy to escape from liquid. Oil requires the most!!
Energy’s Role Energy: The ability to change or move matter.
The Changes of State for Water Evaporation: The change of a substance from a liquid to a gas = cooling process Condensation: The change of a substance from a gas to a liquid = heating process: (must have a surface for it to condense on!!!) Sublimation: The change of a substance from a solid to a gas.
Changes of State for Water: Page 49 Fig. 2-14 pg. 49 L A T I V N G Y
Examples Evaporation = liquid to gas ex: sweat Condensation gas to liquid ex: cold can of pop sweats Sublimation = solid to gas ex: Dry Ice: Directly from solid to gas
Graphic Organizer: Changes of States Of Water Sublimation Boiling or Evaporation Melting Gas Solid Liquid Freezing Condensation
Law of Conservation of Matter Law of Conservation of Energy Mass cannot be created or destroyed (Matter can change from one form to another but the total mass stays the same.) Energy cannot be created or destroyed (Energy can be changed from one form into another but total amount stays the same.)
Were You Paying Attention? Define energy State the Law of Conservation of Energy and the Law of Conservation of Mass. List two examples for each of the three common states of matter. Rank the following in order of increasing strength of forces between molecules. a. Honey b. Marble c. Water d. Nitrogen Gas e. Candle Wax
Continued…. Compare and contrast the shape and volume of solids, liquids, and gases. Predict which two of the following involve the same energy transfer. Assume that the same substance and the same mass is involved in all four processes: a. Melting b. Sublimation c. Evaporation d. Condensation
Continued Describe the energy transfers that occur when ice melts and water vapor condenses to form liquid water. Homework: Creative Thinking: Describe a characteristic of gases, and use the kinetic theory to explain how a dog could find you by your scent.