Properties of Water, Biology

•  Water is a key component of cell structures processes that are necessary for the transfer of matter & energy between life and its surroundings.
• Water is a chemical compound made up of the atoms 2 hydrogens, and one oxygen. H2O
• Atoms rarely exist as individual particles. Water, like most substances is made of atoms held together by Chemical bonds. 
• During the formation of chemical bonds, an atom may lose, share on gain electrons.

2 main types of Chemical Bonds:

1. Ionic Bond: attraction of a positively charged ion to a negatively charged ion. Atoms can gain or lose electrons to become charged ions.

Because of this opposite attraction, ionic bonds are strong. lonically bonded atoms create ionic compounds.

Ex: Table salt, sodium chloride,( NaCl) —attraction between positive sodium ion( Na+) a negative chloride( Cl-) 

2. Covalent Bond: forms when 2 atoms overlap their outer energy levels in order to share valence elections. The shared electrons are attracted to the nuclei of both atoms. Covalent compounds are also called molecules.
is formed by covalent bandes

• Water is formed by covalent bonds.

Bonding in Water:

• Covalent bonds in water involve an uneven sharing of electrons. Oxygen atom's nucleus attract the shared elections more strongly than the hydrogen nuclei. Since electrons are negatively changed the uneven sharing gives the oxygen part a partial negative charge & the hydrogen part a partial positive charge. The water molecule has no overall charge, but has a positive and a negative end.

The charged ends of one water molecule are attracted to the opposite charged regions of its neighboring water molecules. This is  Hydrogen Bonding.

• Hydrogen Bonding: a weak attraction between a slightly positive H atom one one polar molecule, and one slightly negative atom (O,N,F) on another polar molecule.

 Main properties of Water:

1. Cohesion: an attraction of the same particles; Water is a polar molecule w/ a slightly negative and positive end. The negative end attracts the positive end of the water molecules. Due to this, water molecules act like tiny magnets and cling.

2. Adhesion: attraction of water to a different substance. The polarity of water attracts many different substances.

Ex: water in a narrow tube: water's surface is higher than the center as it adheres to the surface of the tube.

3. Surface Tension: A measure of how different it is to stretch/ break the surface of a liquid. Hydrogen bonding in water molecules gives it a strong surface tension. Hydrogen bonds pull from the sides + bottom, but not the top. This uneven bonding pulls surface molecules down and closer.

—Surface Tension almost forms a thin, invisible film on the water's surface. 

4. Capillary Action: Movement of water through a narrow tube. Occurs when forces of cohesion, adhesion, and surface tension work together. (Ex: water movement through a plant).

• In a plant, the water molecule @ the susface of the leaf is attracted to the water molecule below it by hydrogen bonding. The top molecule begins to evaporate, and it pulls on the molecule below. Process repeates. These molecules also adhere to the sides to prevent back flow.

 Expands when Freezes:

• Water is one of the few substances that expands when frozen. When water freezes, hydrogen bonding between molecules causes them to form rigid hexagons. This specific arrangement requires more space, which is why ice is less dense, & it can float
• Density- ratio of mass to volume.
• One L of liquid water weighs more than I L of ice, as there are fewer water molecules in ice. This helps marine life.

Universal Solvent: 

• Water is called this as many things dissolve in water. Ionic compounds like salt dissolve, and polar molecules like sugar dissolve.
• Positive and negative changes attract, which is why it dissolves.

Neutral PH:

• measure of the Hydrogen ions
•  PH scale is from 1-14.
•  Pure water is a neutral substance w/ aph of 7.
• Below 7 are acidic. Higher H+ lons, more acidic.
• Above 7 are bases.