WHY IS A WATER MOLECULE POLAR? Bellwork

WATER BioChemistry

Recap from Friday Review  Water serves important biological functions because of it’s chemical structure  Hydrogen and oxygen in water share electrons in a covalent bond Oxygen “pulls” on the electron bond more than the hydrogen does Makes oxygen more electronegative Results in a slightly negative oxygen atom and a slightly positive hydrogen

The polar nature of water molecules to be attracted to one another  The negatively charged oxygen is attracted to the positively charged hydrogen of another water molecule  Known as a hydrogen bond  Can form, break, and reform easily  Occurs more easily in hot water Hydrogen bonding accounts for the unique properties of water Target #8- I can explain how a hydrogen bond forms

Background Attractive forces between molecules of the same type are called cohesive forces. Attractive forces between molecules of different types are called adhesive forces.

Target #9- I can explain how surface tension is produced by cohesion Cohesion  An attraction between molecules of the same substance  Causes water molecules to be drawn together  Produces surface tension Explains why some insects and spiders can walk on the surface Caused by the strength of molecules holding onto each other

Target #10- I can identify capillary action is occurring when provided an example Adhesion  An attraction between molecules of different substances  Causes water molecules to be attracted to other types of molecules  Ex: water poured into a graduated cylinder dips in the middle Water molecules are more attracted to the glass than each other  Causes capillary action  Occurs when water rises through a tube against gravity Ex: water up the trunk of a tree

Target #11- I can define the high heat capacity of water Heat Capacity  It takes a large amount of heat energy to cause water molecules to move faster, which raises the temperature of water  Therefore, the amount of heat needed to raise water’s temperature is very high

Target #12- I can state why water is considered a universal solvent Universal solvent  Water can dissolve other substances easily  This means that wherever water goes, either through the ground or through our bodies, it takes along valuable chemicals, minerals, and nutrients.

What property of water allows for some insects and spiders to walk on water? A- univeral solvent B- high heat capacity C- low density of ice D-adhesion E- cohesion Checking for understanding

Blood in the human body, which is made mostly of water, is pumped 5 litres per minute. Half the time, it is travelling up to the heart. What property of water allows blood to travel in this direction? A- univeral solvent B- high heat capacity C- low density of ice D-adhesion E- cohesion Checking for Understanding