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Unit 5 Gas Laws & Thermochemistry

Unit 5 Gas Laws & Thermochemistry. Learning Targets: 5.1 I can describe the principles of Kinetic Molecular Theory I can describe what atmospheric pressure is I can describe how temperature related to motion Explain the difference between solids, liquids, and gases at the molecular level.

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Unit 5 Gas Laws & Thermochemistry

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  1. Unit 5Gas Laws & Thermochemistry Learning Targets: 5.1 I can describe the principles of Kinetic Molecular Theory I can describe what atmospheric pressure is I can describe how temperature related to motion Explain the difference between solids, liquids, and gases at the molecular level. I can interpret phase diagrams and describe the factors that affect changes of state 5.2 I can apply the Gas Laws to solve a given problem I can convert between units of measurement for pressure and temperature Apply the Gas Laws to solve a given problem Identify the 4 variables that influence gases, and explain the relationships between: Pressure and Volume Pressure and Temperature Volume and Temperature Solve problems (including stoichiometry problems) using the Ideal Gas Law 5.3 I am able to demonstrate the principles of thermochemistry Explain the relationship between energy & heat Calculate changes in heat & energy in chemical & physical processes Calculate heat & energy changes in phase changes. I can define heat within a system, specific heat, and heat capacity.

  2. Today: 5.1: I can describe the principles of Kinetic Molecular Theory • Explain the difference between solids, liquids, and gases at the molecular level. • I can describe how temperature related to motion • I can describe what atmospheric pressure is • I can interpret phase diagrams and describe the factors that affect changes of state

  3. Variable shape, variable volume Gases: Solids: Have a fixed shape, fixed volume Very low Kinetic Energy (KE) - particles are vibrating, but can’t move around Liquids: Have variable shape, but fixed volume Low KE- particles can move around, but still stay very close together High KE- particles can move away from each other and take the shape of their container.

  4. Kinetic Energy and States of Matter Solid - very low kinetic energy (KE) Liquid - low KE, particles can move around Gas - high KE, particles move freely & randomly

  5. Factors that affect change in state • Temperature – representation of Kinetic Energy • Pressure – The collisions acting against molecules • Volume- the space available for molecules to move in • N- the Number of molecules.

  6. Units:Temperature Temperature is really the measurement of Kinetic Energy of the particles involved. Kinetic Energy is due to the mass & the speed of the particles. • High temperature means that particles are moving at higher speeds. Kelvin is the unit that we use to measure Kinetic Energy

  7. Scales of Temperature Celsius vs. Fahrenheit 0 °C = 32 °F 100 °C = 212 °F

  8. Scales of Temperature William Thompson a.k.a. Lord Kelvin Absolute temperature scale  Kelvin (K) At 0 K all motion stops  time stops

  9. Scales of Temperature

  10. Units: Pressure Pressure is the amount of force an object puts upon a defined area • In the case of gases, the Pressure can be described as the collisions of the individual gas particles on the sides of the container. • KEY UNITS AT SEA LEVEL • 101.325 kPa (kilopascal) • 1 atm (atmosphere) • 760 mm Hg • 760 torr • 14.7 psi

  11. Atmospheric Pressure At sea level 1 atm = 14.696 lb/in2 = 101.3 KPa (kilopascals) = 760 mm Hg = 760 torr (antiquated measure) = 1,013.25 mbar (stupid US unit) = 1.01325 bar

  12. Atmospheric Pressure Atmospheric pressure decreases rapidly with height. Climbing to an altitude of only 5.5 km where the pressure is 500 mb, would put you above one-half of the atmosphere’s molecules.

  13. H2O 218 Phase Diagrams

  14. Phase Diagrams Triple point - where the (s), (l), and (g) co-exist Critical point - where phase boundaries cease to exist A supercritical fluid is any substance at a temperature and pressure above its critical point. It can diffuse through solids like a gas, and dissolve materials like a liquid. Supercritical fluids are suitable as a substitute for organic solvents in a range of industrial and laboratory processes. Carbon dioxide and water are the most commonly used supercritical fluids, being used for decaffeination and power generation respectively *

  15. Kinetic Molecular Theory (KMT) Kinetic energy  derived from motion • KMT has three main tenets: • Random motion - no attractive or repulsive forces between particles • Newtonian Motion • All collisions are perfectly elastic

  16. Kinetic Molecular Theory (KMT) • Newton’s Laws of Motion • An object remains at rest/motion until an outside force acts upon it • F = ma • To every action there is an equal and opposite reaction

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