Water Flashcards
When are molecules described as polar?
When the atom with the greater share of negative electrons will be slightly negative (delta-) compared to the other atom in the bond which’s be slightly more positive.
These molecules have regions of negativity and positivity
Give examples of polar molecules?
Oxygen & Hydrogen. Oxygen always has a much greater share of electrons in an O-H bond. Many organic molecules contain oxygen & hydrogen bonded together in what are called hydroxyl groups and so they are slightly polar.
What’s a hydrogen bond?
When polar molecules, including water, interact with each other as the positive and negative regions of the molecule attract each other and form bonds, called Hydrogen bonds.
Are hydrogen bonds weak or strong?
they are weak interactions, which break and reform between the constantly moving water molecules
How does hydrogen bonding impact water?
It gives water its unique characteristics which are essential for life on this planet.
Although these bonds are weak, they occur in high numbers.
Explain this characteristic of water: High Boiling Point
Although It is much lighter than CO2 and O2, water is a liquid at room temperature.
This is due to to the hydrogen bonding between water molecules.
It takes a lot of energy to increase the temperature of water and cause water to become gaseous (evaporate)
Explain this characteristic of water: Freezing
When water freezes it turns to ice
Most substances are more dense in their solid state than in their liquid state, but when water turns to ice it becomes less dense. This is because of the hydrogen bonds formed.
How does ice float?
Because as water is cooled below 4*C, the hydrogen bonds fix the positions of the polar molecules slightly further apart than the average distance in a liquid state.
This produces a giant, rigid structure with every oxygen atom at the centre of a tetrahedral arrangement of hydrogen atoms, resulting in a solid that is less dense than liquid water
Explain water’s cohesive properties
It moves as one mass because the molecules are attracted to each other (cohesion)
It is in this way that plants are able to drink up water from their roots and how you are able to drink from a straw.
Cohesion can also cause surface tension
Explain water’s adhesive properties
This is where waiter molecules are attracted to other materials
For example. When you wash your hands, they become wet, the water doesn’t just run straight off
Adhesion also causes a meniscus in a measuring cylinder
Explain how water acts as a Solvent
Because it is a polar molecule, in which many of the solutes in an organism can be dissolved.
(The cytoplasm of prokaryotes and eukaryotes is mainly water)
Water acts as a medium for chemical reactions and also helps transport dissolved compounds in and out of cells
Explain how water makes an efficient transport medium within living things
Because cohesion between water molecules mean that when water is transported through the body, molecules will stick together.
Adhesion occurs between water molecules & other polar molecules and surfaces
The effects of adhesion and cohesion result in water exhibiting Capillary Action
What is Capillary Action?
The process by which water can rise up a narrow tube against the force of gravity
Explain how water can act as a coolant
It helps to buffer temperature changes during chemical reactions in prokaryotic and eukaryotic cells because of large amounts of energy required to overcome hydrogen bonding.
Maintaining constant temperatures in cellular environments is important as enzymes are often only active in a narrow temperature range
Explain how water is stable
Many organisms (fish) live in water and cannot survive out of it.
water is stable - it does not change temperature or become a gas easily , therefore providing a constant environment
