Water and ice physical properties and its structure-1.pptx

Materials for food technology students

1. Water and ice physical properties and its structure G BHARATHI Assistant Professor Department of Food and Dairy Technology Mannar Thirumalai Naicker College Madurai

2. The Water Molecule H 2 O Covalent bond Polarity

3. Polarity of water

4. Dissolving Property of Water

5. States of Water

6. Latent Heat

7. Latent Heat

8. Heat Capacity of Water

9. Viscosity of Water

10. Surface Tension of Water

11. Unique Property of Water

12. Density of Water Temperature Salinity

13. Transmission of Light

14. Transmission of Sound Sound and Locating Objects

15. Organisms Depend on Cohesion Cohesion is responsible for the transport of the water column in plants Cohesion among water molecules plays a key role in the transport of water against gravity in plants Adhesion, clinging of one substance to another, contributes too, as water adheres to the wall of the vessels.

16. Structure of water and ice

17. Liquid water has a partially ordered structure in which hydrogen bonds are constantly being formed and breaking up. The strong hydrogen bonds also give water a high cohesiveness and, consequently, surface tension. This is evident when small quantities of water are put onto a non-soluble surface and the water stays together as drops.

18. A schematic of the crystal structure of hexagonal ice Each H 2 O molecule has its four nearest neighbors arranged near the vertices of a regular tetrahedron (shaded) centered about the molecule of interest. Near the melting point the O-O distance is 0.276 nm, and the lattice parameters are a = 0.4523 nm and c = 0.7367 nm. Ice possesses 12 different crystal structures, plus two amorphous states.

19. At ordinary (low) pressures the stable phase is termed ice I. There are two closely related variants: hexagonal ice Ih , whose crystal symmetry is reflected in the shape of snowflakes, and cubic ice Ic . Ice Ih is obtained by freezing water; ice Ic is formed by depositing vapor at low temperatures ( -130°C). Amorphous ice can be obtained by depositing vapor at still lower temperatures and by compressing ice Ih at liquid nitrogen temperature. In addition to the elemental phases are clathrate hydrates. These are crystalline compounds composed of a large H 2 O cage in which Xe , Ar , or CH 4 , for instance, is entrapped. Clathrates are of economic interest because they offer an abundant source of natural gas.

20. Ice floats because it is less dense than water. Water has a density of 1.0 gm/cubic cm. The density of ice Ih is 0.931 gm/cubic cm. But, why is ice less dense than water if both are made up of molecules of H 2 O? In liquid water each molecule is hydrogen bonded to approximately 3.4 other water molecules. In ice each molecule is hydrogen bonded to 4 other molecules.

21. Compare the two structures below. Notice the empty spaces within the ice structure. Water caption Ice caption In ice Ih , each water forms four hydrogen bonds with O---O distances of 2.76 Angstroms to the nearest oxygen neighbor. The O-O-O angles are 109 degrees, typical of a tetrahedral coordinated lattice structure. The density of ice Ih is 0.931 gm/cubic cm. This compares with a density of 1.00 gm/cubic cm. for water

22. There are twelve different forms of crystalline ice that are know. The hexaganol form known as ice Ih is the only one that is found naturally. The lattice structure of ice 1h is shown here

23. Thank you