Water Flashcards
What is a covalent bond?
Bond formed when atoms share electrons
What is a polar covalent bond and why does it form
Bond formed by the unequal sharing of electrons
The nucleus of the oxygen atom is more attractive to electrons as compared to the nuclei of hydrogen atoms
Why does O have partial negative charge and H partial positive charge
1) Because of polarity, unequal sharing of electrons
2) Water molecules are bent rather than linear, 2 H atoms are on the same side forming a pole
Define hydrogen bond
The intermolecular force formed when a hydrogen atom in one polar molecule is attracted to a slightly negative atom of another polar covalent molecule (in this case, oxygen)
If hydrogen bonds are weak how is the attraction so strong
Because water molecules are small, so there are many of them per unit volume
What are the properties of water? what explains them?
Cohesion
Adhesion
High Specific heat capacity
High latent heat of vapourisation
High boiling point
Solvent
Hydrogen bonding and dipolarity explain them
What is cohesion?
Refers to the binding together of two molecules of the same type, eg water molecules
Application of cohesion
Water is sucked through the xylem at low pressure, and this is only possible if the water molecules are not separated by forces. Cohesion keeps them together
Cohesion leads to surface tension- because of which lighter insects skate on the surface
What is adhesion
Hydrogen bonds formed between water and other polar molecules
Application of Adhesion
Water adheres to the cellulose in the cell wall of plant cells. If water evaporates from the cell wall, adhesion causes water to be drawn out from nearby xylem vessels keeping the walls moist to absorb CO2
Water wets cloth
What is specific heat capacity
The amount of energy required to increase the temperature of 1g of a substance by 1C
Why does water have high specific heat capacity
Increases in temperature require hydrogen bonds to break, and they restrict the motion. Large amount of energy is required to increase or decrease the temperature even by a small amount.
Applications of High specific heat capacity
Stable habitat for aquatic animals, lakes don’t freeze over
Formentation
What is High latent heat of vapourisation
The amount of energy required to change 1g of water in it’s liquid state to it’s gaseous state at constant temperature.
Why does water have a high latent heat of vapourisation
Considerable amounts of heat are required to to break the hydrogen bond
Applications of High latent heat of vapourisation
Sweating
What is boiling point
The highest temperature of a substance that it can reach in a liquid state.
Why does water have a high boiling point
A large amount of energy is required to break the hydrogen bonds
Why is water a good solvent
The polar nature of water means it forms shells around charged and polar molecules preventing clumping. Both poles dissolve positively charged particles and negatively charged particles respectively
What is cytoplasm
A complex mixture of of dissolved substances in which the chemical reactions of metabolism occurs
What are hydrophobic and hydrophilic substances
Hydrophilic- water loving, describes substances that are chemically attracted to water, all substances that dissolve, polar molecules of glucose, sodium, chloride, cellulose
Hydrophobic- insoluble, non polar, lipids, fats, oils
What happens if a non polar molecule is surrounded by water molecule
hydrogen bonds form between the water molecules around the non polar ones
the non polar molecules are slightly attracted to each other, like oil drops
