Lesson 3 - Water Flashcards
Which part of water molecule is negative and which is positive
The Oxygen is partially negative
The hydrogen is partially positive
What is electronegativity
the measure of an atom’s pull on a bonded pair of electrons
Main properties of water and their uses
- a metabolite in many metabolic reactions: condensation and hydrolysis reactions
- an important solvent in which metabolic reactions occur
- has a relatively high heat capacity, buffering changes in temperature
- has a relatively large latent heat of vaporisation, providing a cooling effect with little loss of water through evaporisation
- has strong cohesion between water molecules; this supports columns of water in the tube-like transport cells of plants and produces surface tension where water meets air
Which bonds are stronger, covalent or hydrogen bonds?
Covalent
Because water is cohesive it results in…
Surface tension
Surface tension allows…
Provides habitats for organisms, e.g. the pond skater
Name 2 practicals that show surface tension
Floating pins
Penny practical
Electronegativity meaning
The measure of an atom’s pull on a bonded pair of electrons
Name the intermolecular bonds and intramolecular bonds in a molecule water
intermolecular bonds - between molecules (hydrogen bond)
intramolecular bonds - within the molecule in between the atoms (covalent bond)
Cohesion definition
Water to water attraction
Adhesion definition
Water to xylem vessel
Hydrophobic definition
Not attracted to water (e.g. fats/oils)
Hydrophilic definition
Attraction for water
How is water a solvent
- It dissolves charged ionic molecules, such as salt (NaCl)
- It also dissolves other polar molecules, such as glucose (sugar), that can form hydrogen bonds with the water molecules (contains OH groups)
Condensation reactions
a chemical reaction in which water is produced when smaller molecules are joined to form a larger molecule
Hydrolysis reactions
a chemical reaction in which a water molecule is needed to break up a large molecule into smaller molecules
water is a solvent and a metabolite… how is it used as a transport medium in animals
plasma in the blood (watery solution) transports dissolved substances eg. sugars, urea, salts, ions
water is a solvent and a metabolite… how is it used as a transport medium in plants
xylem vessels transport water and dissolved minerals. Phloem transports water and dissolved sucrose and amino acids
Definition of a high specific heat capacity
A large amount of energy is required to raise the temperature by 1 degrees
Positives about water having a high specific heat capacity
water buffers changes in temperature and so it is thermostable, providing a stable environment for aquatic organisms.
Does water have a small or large latent heat of vaporisation?
A large amount of energy is required to evaporate water
Density and freezing (apply to water)
• As water freezes it expands (water molecules are held further apart by hydrogen bonds) therefore frozen water is less dense than liquid water therefore floats
• The frozen ice layer insulates the water below it therefore the water below doesn’t freeze (allowing sustained life below)
Positives of water being transparent
Light travels through water allowing aquatic plants/algae to photosynthesise
