Chapter 2 - Water Flashcards
What makes up a water molecule?
Two hydrogen molecules covalently bonded to 1 oxygen molecule, forming a triangular shape
What is a covalent bond?
A strong chemical bond formed by sharing one or more electrons between two atoms, forming a molecule
What is a polar molecule?
A molecule with regions of negative and positive charge
Why does the water molecule have an overall neutral electrical charge?
Because the the overall oxygen charge is slightly negative and the overall hydrogen charges are slightly positive so balance each other out
Why do two separate water molecules attract one another?
Because of weak hydrogen bonds, which form between a hydrogen and oxygen atom of adjacent water molecules
What can water molecules do, due to there attraction to one another?
Flow together as a liquid, and are attracted to all charged molecules/surfaces
Why do hydrogen bonds need to be weak between adjacent water molecules?
So that the bonds can form and break easily, water flows quickly
Why is water an ideal habitat?
It remains a liquid between 0-100 degrees which is perfect for living things to survive in
Why is water an efficient coolant?
It has a high specific heat capacity (absorbs a great amount of heat relative to its mass)
What happens to water at 0 degrees or lower?
The molecules loose KE and hydrogen bonds stop breaking easily, forming a rigid structure that no longer flows
What happens to water at 100 degrees?
The hydrogen bonds are weakened by the heat and escape one another, water becomes gas (water vapour)
What happens to water at 0 degrees, precisely?
The newly forming solid water/ice is less dense than the water underneath it, so this sheet of ice floats on top of the water, providing an insulating layer which keeps the water underneath at a constant temperature (where living things may still survive)
What is a solution?
A solvent (the liquid), with dissolved solutes in it (solids/liquids/gasses)
How does water act as a solvent?
It surrounds the solute molecules, keeping them in a solution
What can easily dissolve in water?
Polar charged molecules
Why can carbon containing molecules (with charged ionised groups, e.g. (COOH-), or amino groups (NH3+) dissolve?
They can form hydrogen bonds with the atoms of there opposite charge e.g. the oxygen will bond to the amino group solutes
How do ionic substances dissolve?
They release pos charged ions (cations) and negatively charged ions (anions) and water clusters around each
Why is water a necessity in living things?
Allows chemical reactions within a cell, allows molecules to be dissolved in the systole, ideal transport medium as dissolves polar molecules & ions
What is cohesion?
Property of water - water molecules are attracted to each other due to hydrogen bonding
What is tension?
A force that tends to stretch something
What is adhesion?
Property of water - water molecules are attracted to surfaces such as walls of cells/vessels/tubes
What creates surface tension?
Hydrogen bonds pulling the molecules inwards at the surface
What happens to non-polar molecules when dissolving in water?
They cannot dissolve, they are hydrophobic and are repelled
