Structure and properties of water

• thermal properties of water
• water freezes and boils at higher temperatures than other similar compounds (Fig)
• water is a polar molecule (Fig)
• concept of hydrogen bonds (Fig)
• heat capacity
• experiment: heating water in a paper tray. Why is the paper not burning?
• About 1 calorie (the basic unit) of heat is needed to raise the temperature of 1g of water by 1^oC (1 calorie (cal) = 4.184 joule (J). Specific heat capacity of water is larger than that for most substances.
• phase changes of water as a function of added heat (Fig)
• latent heat of vaporization (539 cal/g or 2255J/g) and fusion (80 cal/g or 335 J/g);
  
• the NY Times had an article in January 2007 about how farmers protected their citrus fruit crop by irrigating with water (Fig)
  
• density of water
• density of water as a function of temperature. Water has its highest density at 4^oC. Water volume increases by 9% when it changes from water to ice (Fig)
• definition of density: mass per volume
• explanation based on hydrogen bond model (Fig)(Fig)(Fig)(Fig)
• viscosity
• definition of viscosity mu (Fig 3.1) F/A = mu * u_plate/d
  
• viscosity of water decreases by 3% per ^oC increase in temperature (Fig A2.1)
• experiment: measuring the flow velocity of cold and hot water in a capillary
• surface tension
• capillarity: in a 1/8 mm diameter tube water would rise more than 25cm (Fig)
• h = 2*sigma / (r*rho*g); sigma: specific surface tension, rho: density, g: gravity constant, r: radius of capillary
• sigma (at 18^oC) = 0.0729 N/m
  
• experiment: suspended paper clip and influence of dishwashing liquid (Fig)
• experiment: measure rise of water in a capillary (ID = 1mm) (Fig)
• adhesion/cohesion
• Absoption of radiation
• large in infrared and ultraviolet regions, less in visible regions (Fig)
  
• compressibility
• compressibility of water is small. An increase of pressure by 1 atmosphere (= 1013mbar = 14.7 psi) causes a decrease of the water volume by 5.3*10^-5 of the original volume.
• solubility
• water is able to dissolve huge quantities of salts and is therefore an important factor in transporting substances in nature
• more than 300g of NaCl can be dissolved in a kg of water
• hydrophobic, hydrophilic substances, soap has hydrophobic & hydrophilic ends, e.g. CH₃(CH₂)₁₆CO₂^-Na⁺
• summary
• Fig

Resources:

1. Manning, J.C. (1997), chapter 2; see books on reserve.
2. Hornberger et al. (1998), Appendix 2.
3. equipment used for experiments