Studied by 17 people
Formula for Water
H2O
What is in the center of an atom?
Nucleus, which contains protons and neutrons
What are the main elements in biology?
Carbon, Hydrogen, Oxygen, Nitrogen
What are the types of chemical bonds?
Ionic and Covalent
How many electrons are in a single bond?
2 electrons
Covalent bonds ________ electrons
share
In ionic bonds, the less electronegative atom _______ electron(s) to the more electronegative atom.
donate
What side of water is slightly negative/more electronegative
The oxygen side
What side of water is slightly positive/less electronegative
The hydrogen side
What is a Hydrogen bond?
A hydrogen bond is NOT a bond, but an attraction between two molecules.
Hydrogen bonds are responsible for these properties of water:
Adhesion
Cohesion
Solvent Properties
Thermal Properties
Creating h bonds ______ heat
releases
Breaking h bonds _____ heat
absorbs
What is the weight of 1 proton/1 neutron
1 Dalton/AMU (Both units are the same)
Electrons have potential energy because…
They are a distance away from the nucleus, but want to connect to the positive charge of the protons in the nucleus.
The first electron shell holds ____ electrons
2
The second & third electron shells hold ____ electrons
8
How do electrons fill in shells?
They fill in without pairs, and only form pairs when they have to.
What are Van der Waals interactions?
Electrons are not always distributed equally in an atom. This makes one side of an atom slightly positive, and the other side slightly negative. This is always happening with all atoms, so the atoms will pull ever so slightly on each other.
Droplets are formed due to…
Surface tension
Force on water molecules at the surface is concentrated ___ and ___
Down and In
How does surface tension help with dispersal of seeds?
Seeds use the surface of the tension, and stay on top of the body of water. It then flows with the water until reaching a new area.
In plants, water is transported through what structure?
Xylem
What is Xylem made of?
Cellulose, with lignin in between to reinforce the walls
Describe the transpiration chain from the leaves down.
The leaves open stomata, which allow for the exit of water. This reduces pressure at the top of the plant. The reduction in pressure, combined with the cohesion of water creating an unbroken chain in the xylem create a siphon, pulling the water molecules up.
What is adhesion?
Adhesion is the attraction between two different molecules (ie NaCl & H2O)
Polar molecules adhere to:
Other polar molecules
Nonpolar molecules adhere to:
Non-polar molecules
What is a general rule of thumb to tell if a molecule is polar?
See if there is an oxygen atom, except in Oxygen-Oxygen bonds (shared equally).
Also, hydrocarbons are ALWAYS nonpolar
What does it mean when water has a high specific heat?
This means that it takes a higher amount of energy to increase the temperature of water.
Why does water have a high specific heat?
Hydrogen bonds
What is evaporative cooling and why does it happen?
Evaporative cooling is when water is secreted out of an organism (sweat), and the highest temperature water evaporates, taking the heat with it. In addition, water vapor has fewer hydrogen bonds, and the breaking of hydrogen bonds absorbs heat.
It’s done to maintain homeostasis.
Note 
Flashcard (39)