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Kinetic Theory. An explanation of the behavior of molecules in matter 3 basic assumptions 1. All matter is composed of small particles (atoms, molecules,

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Presentation on theme: "Kinetic Theory. An explanation of the behavior of molecules in matter 3 basic assumptions 1. All matter is composed of small particles (atoms, molecules,"— Presentation transcript:

1 Kinetic Theory

2 An explanation of the behavior of molecules in matter 3 basic assumptions 1. All matter is composed of small particles (atoms, molecules, and ions) 2. These particles are in constant, random motion 3. These particles are colliding with each other and the walls of their container

3 Thermal Energy The total energy of a material’s particles Kinetic energy + potential energy AVERAGE KINETIC ENERGY=TEMPERATURE Faster moving particles = higher temp. Slower moving particles =lower temp. Absolute zero = C (particle motion is so slow that no additional thermal energy can be removed)

4 Solid State Has a definite shape and volume Particles are closely packed together and vibrating in place Particles have a geometric arrangement

5 Liquid State Has a definite volume, but no definite shape Particles slip out of their ordered arrangement and are able to move past each other Still some attractive forces

6 Liquid State Melting point – The temp. at which a solid begins to liquify Heat of fusion – The amount of energy required to change a substance from the solid phase to the liquid phase at its melting point

7 Gas State No definite shape or volume Particles have enough kinetic energy to overcome the attractive forces between them Particles bounce and collide, filling their container

8 Gas State Boiling point – the temperature at which the pressure of the vapor in the liquid is equal to the external pressure acting on the surface of the liquid Heat of vaporization – the amount of energy required for the liquid at its boiling point to become a gas

9 Gas State Evaporation Boiling Occurs at the surface of a liquid Can occur at temperatures below the boiling point Must have enough kinetic energy to escape the attractive forces of the liquid Occurs throughout a liquid Occurs at a specific temp.

10 Diffusion Spreading of particles throughout a given volume until they are uniformly distributed Occurs in solids and liquids, but most rapidly in gases From high concentration to low concentration

11 Heating Curves Shows temp. change as thermal energy (heat) is added Temp. remains constant during melting and while boiling All energy is used to overcome attractive forces

12 Thermal Expansion An increase in the size of a substance when the temp. is increased Solids (gaps in sidewalks) Liquids (thermometers) Gases (hot air balloons)

13 The Strange Behavior of Water Water molecules have highly positive and negative areas As they cool, molecules align themselves by charge, so empty spaces occur in the structure Water expands as it goes from liquid to solid Ice is less dense than water (that’s why it floats!)

14 Plasma State Matter consisting of positively and negatively charged particles (neural charge overall) Very high energy  hard collisions of molecules  electrons stripped off Ex - stars, lightning bolts, neon tubes, etc.

15 Amorphous Solids Not all solids have a definite melting point Some merely soften and turn into liquid over a range of temps. They lack the ordered structures of crystals Ex - glass and plastic (long, chainlike molecules)

16 Liquid Crystals Start to flow during the melting phase similar to a liquid, but they do not lose their ordered arrangement completely Highly responsive to temperature change and electric fields Ex - LCD displays of watches, clocks, and calculators

17 Changes in Thermal Energy Experiment 1. Create a time/temperature table 2. Fill your beaker halfway with ice and cold water 3. Use your thermometer to measure the temperature of the water (DO NOT TOUCH THE THERMOMETER TO THE SIDES OR BOTTOM OF THE BEAKER) Record this temp. as time zero 4. Place your beaker on a hot plate over medium heat 5. Measure the temperature every minute and record it in your table 6. Create a graph using your data. 7. Write a paragraph describing what is happening in your graph.


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