1. 1. Prepared by :- Abhishek
2. 2. Observing the Natural World of Matter What Is Matter? Matter is the material or stuff everything is made of. What are you doing if you are observing matter? Observing matter means to carefully explore all of its properties. Look around the room and identify some matter. What are some physical properties matter can have? Color, texture, odor, shape What are two properties that all matter share? All matter has mass and takes up space. What are the three states of matter? solid, liquid, and gas
3. 3. Solid, Liquid, Gas (a) Particles in solid (b) Particles in liquid (c) Particles in gas
4. 4. Ice H2O(s) Ice Photograph of ice model Photograph of snowflakes
5. 5. Liquid H2O(l) Water In a liquid molecules are in constant motion there are appreciable intermolecular forces molecules are close together Liquids are almost incompressible Liquids do not fill the container
6. 6. Gas H2O(g) Steam
7. 7. Liquids The two key properties we need to describe are EVAPORATION and its opposite CONDENSATION add energy and break intermolecular bonds EVAPORATION release energy and form intermolecular bonds CONDENSATION
8. 8. States of Matter Solid Liquid Gas Holds Shape Fixed Volume Shape of Container Free Surface Fixed Volume Shape of Container Volume of Container heat heat
9. 9. Some Properties of Solids, Liquids, and Gases Property Solid Liquid Gas Shape Has definite shape Takes the shape of Takes the shape the container of its container Volume Has a definite volume Has a definite volume Fills the volume of the container Arrangement of Fixed, very close Random, close Random, far apart Particles Interactions between Very strong Strong Essentially none particles
10. 10. To evaporate, molecules must have sufficient energy to break IM forces. Molecules at the surface break away and become gas. Only those with enough KE escape. Breaking IM forces requires energy. The process of evaporation is endothermic. Evaporation is a cooling process. It requires heat. Evaporation
11. 11. Change from gas to liquid Achieves a dynamic equilibrium with vaporization in a closed system. What is a closed system? A closed system means matter cant go in or out. (put a cork in it) What the heck is a dynamic equilibrium? Condensation
12. 12. As time goes by the rate of vaporization remains constant but the rate of condensation increases because there are more molecules to condense. Equilibrium is reached when: Rate of Vaporization = Rate of Condensation Molecules are constantly changing phase dynamic The total amount of liquid and vapor remains constant equilibrium Dynamic Equilibrium
13. 13. Vaporization is an endothermic process - it requires heat. Energy is required to overcome intermolecular forces Responsible for cool earth Why we sweat Vaporization
14. 14. Energy Changes Accompanying Phase Changes Solid Liquid Gas Melting Freezing Deposition CondensationVaporization Sublimation Energyofsystem
15. 15. Density & Specific gravity Density:-The density of a material is equal to its mass divided by its volume and has units of 3 . It is of two types:- Bulk Density Particle Density What is porosity? Surface Gravity: SG = density of liquid / density of water
16. 16. Viscosity Viscosity may be thought of as a liquids internal resistance to flow. A liquid can be envisaged as having a series of layers and when it flows over a surface, the uppermost layer flows fastest and drags the next layer along at a slightly lower velocity, and soon through the layers until the one next to the surface is stationary.
17. 17. Van der Waals Forces and the Properties of Liquids Viscosity increases with increasing intermolecular forces because increasing these forces increases the resistance to flow. Other factors, such as the possibility of molecules tangling together, affect viscosity. Liquids with long molecules that tangle together are expected to have high viscosities.
18. 18. Continue Pseudo plastic fluid Viscosity decreases as the shear rate increases (e.g. emulsions, and suspensions such as concentrated fruit juices and puries) Dilatant fluid Viscosity increases as the shear rate increases. (This behaviour is less common but is found with liquid chocolate and corn flour suspension.) Binghamor Casson plastic fluids There is no flow until a critical shear stress is reached and then shear rate is either linear (Bingham type)or non-linear ( Casson type)(e.g. tomato ketchup) Thixotropic fluid The structure breaks down and viscosity decreases with continued shear stress ( mostcreams) Rheopectic fluid The structure builds up and viscosity increases with continued shear stress ( e.g.whippingcream)
19. 19. Surface Tension Surface tension is the tendency for liquid surface to contract. Depends on attractive forces Compounds that interfere with the forces and reduce surface tension are called surfactants.
20. 20. Van der Waals Forces and the Properties of Liquids Surface tension increases with increasing intermolecular forces. Surface tension is the energy needed to reduce the surface area of a liquid. To increase surface area, it is necessary to pull molecules apart against the intermolecular forces of attraction.
21. 21. The molecular basis of surface tension. hydrogen bonding occurs in three dimensions hydrogen bonding occurs across the surface and below the surface the net vector for attractive forces is downward
22. 22. Shape of water or mercury meniscus in glass. adhesive forces stronger cohesive forces H2O capillarity Hg
23. 23. The striking beauty of crystalline solids.
24. 24. portion of a 3-D lattice The crystal lattice and the unit cell. lattice point unit cell portion of a 2-D lattice unit cell
25. 25. Phase Changes
26. 26. Phase Changes solid liquid gas melting freezing vaporizing condensing sublimination Energy absorbed Energy released
27. 27. Quick Review to what we have studied so far.