Water Flashcards
What are covalent bonds?
Covalent bonds are formed when two atoms share a pair of electrons
What is polarity?
In some covalent bonds, the nucleus of one of the atoms is more attractive to electrons than the other (higher electronegativity) so the electrons are not shared equally.
The consequence of this is that part of the molecule has a slight positive charge and another part has a slight negative charge.
Why are water molecules polar?
Water molecules are polar as oxygen is more attractive to electrons than the two hydrogen atoms, thereby making oxygen slightly negative and the two hydrogen molecules slightly positive.
What is a hydrogen bond?
Hydrogen bonds are those formed between the partially positive hydrogen atoms in water with partially negative atoms of other polar molecules.
Are hydrogen bonds strong?
Although hydrogen bonds individually are weak, in water a large number of the bonds are formed, making it a strong bond.
What is cohesion?
Cohesion refers to the binding together of two molecules of the same type. Water molecules cohere because of the hydrogen bonds that form between them.
What are 2 applications of cohesion?
- Due to cohesion, water molecules stick together even while being transported in xylem vessels (where there is a large amount of suction forces)
- High surface tension allows organisms to move along its surface
What is adhesion?
The dipolarity of water molecules makes them adhere to surfaces that are polar. The hydrogen bonds form between water and other polar molecules.
What are 2 applications of adhesion?
- Adhesion between water and cellulose in cell walls keep the cell walls moist, benefiting them during gas exchange
- Adhesion plays a role in capillary action (that is, it helps water move up plant stems in opposition of gravitational forces)
What are the thermal properties of water?
Due to the extensive hydrogen bonding, water has high melting and boiling points, high latent heat of vaporization, and a high specific heat capacity.
What are 2 applications of the thermal properties of water?
- The high specific heat capacity makes water’s temperature change relatively slowly, making it suitable for living organisms
- Due to the high specific heat capacity of water, it can take up heat without changing in temperature, thereby acting as a coolant
What are the solvent properties of water?
Water is regarded as a universal solvent due to its ability to dissolve a large number of substances. Any substances that contains charged particles (ions) or are polar can dissolve in water.
What are hydrophilic substances?
Hydrophilic substances are those that are attractive to water and form inter-molecular bonds with water molecules.
Include all polar molecules and ions.
What are hydrophobic substances?
Hydrophobic substances are those that do not freely associate or dissolve in water as bonds between water molecules are stronger than that of bonds between the hydrophobic substance and water.
Include large, non-polar molecules like fats and oils.
How does sweat act as a coolant?
In order for sweat to evaporate from the surface of the body, heat is transferred from blood circulating under the surface of the skin. Since water has a high latent heat of vaporization, it absorbs a lot of heat before evaporating, thereby having a cooling effect on the body.
