Kinetic Molecular Theory

1. THE KINETIC MOLECULAR THEORY

2. BASIC ASSUMPTIONS 1. Matter is made up of tiny, basic units of structure called “atoms” 2. Atoms are neither divided, created, nor destroyed during a physical or chemical change. 3. An element is made up of its own kind of atom, which is different from the atoms of other elements. A. Molecules

3. 4. Compounds are composed of atoms of two or more elements that join together in definite proportions. Molecule – a tightly bound group of atoms in which the atoms maintain their identity; smallest ultimate particle of matter than can exist; smallest particle of a compound, or a gaseous element that can exist and still retain the characteristic properties of a substance.

4. Take Note: Some atoms of gases exist in nature as diatomic molecules – 2 atoms of the same element paired together. B. Molecules Interact 1. Cohesion forces – (n. cohesion) attractive force between molecules of the same kind. 2. Adhesive force – (n. adhesion) attractive force between molecules of the same kind.

8. D. Molecules Move “ Molecules of a gas will bounce around among the molecules of the air, slowly until it becomes evenly distributed.” (process of diffusion) Diffusion - mix with another substance by movement of particles. Take Note: Rudolf Clausius – “temperature is proportional to the average kinetic energy of its molecules ~ the greater the temperature, the greater is its molecules’ motion”

9. TEMPERATURE The degree or intensity of heat present in a substance or object ~ how hot or how cold is something. A. Thermometers An instrument for measuring the hotness or coldness of an object. 1. Dial thermometer – bimetallic strips 2. Glass thermometer – Mercury or Colored alcohol

11. 2. Celsius Scale – (named after Swed. astronomer Anders C. Celsius ) based on the freezing and boiling point of water at normal atmospheric pressure ~ 0 ºC - freezing pt. and 100ºC – boiling pt.

12. 3. Kelvin Scale – (named after Brit. physicist William T. Kelvin ) erased the arbitrary assigned reference points, thus called not a relative scale but an Absolute temperature scale . 0 = nothing – Absolute Zero ~ lowest temperature possible, occurring when all random motion of molecules has ceased. In this scale: 273K – freezing pt. of water; 373K – boiling pt.

13. HEAT Used to describe the movement of energy between objects of different temperature are brought together; is the measure of the internal energy that has been absorbed or transferred from one body to another.

14. A. Measures of Heat Calorie – the amount of energy required to increase the temperature of 1 g of water by 1 °C. Kilocalorie – the amount of energy required to increase the temperature of 1 kg of water by 1 °C.

15. British Thermal Unit (BTU) – the amount of energy required to increase the temperature of 1 lb of water by 1 °F.

17. B. Significance of the variables 1. The amount of heat required is proportional to the change in temperature. 2. The amount of heat required is proportional to the amount of liquid. 3. Different materials require different amounts of heat .

18. HEAT FLOW A. Conduction - the transfer of energy from a region of high temperature to a region of low temperature ~ energy is transferred from one molecule to another . B. Convection - transference of mass or heat within a fluid caused by the tendency of warmer and less dense material to rise.

19. C. Radiation - energy emitted as electromagnetic waves or subatomic particles ; (radiant energy ~ energy that can move through space).

21. 1. Evaporation – liquid to gas 2. Condensation – gas to liquid 3. Freezing – Liquid to solid 4. Melting – solid to liquid 5. Sublimation – solid to gas 6. Deposition – gas to solid B. Latent Heat of Fusion The heat involved in a solid-liquid phase change in melting or freezing.

22. B. Latent Heat of Vaporazation The heat involved in a liquid-gas phase change where there is evaporation or condensation. EVAPORATION AND CONDENSATION A. Increasing the rate of evaporation 1. Increasing the temperature

23. 2. Increasing the surface area 3. Removal of water vapor from the surface of the liquid 4. Increasing pressure