Biology Unit 2 Test -- Hydrogen bonds
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47 Terms
Subatomic particles
Protons, neutrons, electrons
Protons
Positive, found inside the central core/nucleus of an atom
Neutrons
Neutral, found inside the central core/nucleus of an atom
Electron
Negative, found outside the nucleus in their “electron shells”
What is an electron shell
The energy levels for electrons
Atomic number
The number of protons in an element
Atomic mass
The total count of protons and neutrons in an atom's nucleus, which approximates the atom's mass
Mass number
The actual mass of a single atom
Isotopes
An atom that have the same protons but different neutron
Radioactive isotopes
Isotopes that nucleus is decaying and releasing energy
Tracers
A substance used to track the processes inside an element
What determines the way elements act
Protons
What is a chemical reaction
The making or breaking of chemical bonds
Where are the reactants and products
L — Reactant
R — Product
What determines how elements ACT when they encounter other elements?
Electrons — They vary in the amount of energy they have — atoms want to be fat and happy
What happens when atoms ARENT fat and happy?
They interact with other atoms and participate in chemical reactions
What is an ion
An atom or molecule with an electrical charge resulting from a gain or loss of 1+ electrons
What is ionic bonding?
Donating and accepting electrons
What is a covalent bond?
Two atoms share 1+ electrons (polar and non polar)
Polar
The unequal sharing of electrons, has a charge, two opposites
Nonpolar
The equal sharing of electrons, no apparent charge
How are polar covalent bonds formed?
Two atoms share electrons unequally
How are nonpolar covalent bonds formed?
When two atoms share electrons equally
What is a hydrogen bond?
The hydrogen atom (+) part of a covalent bond whos positive charge allows it to share attractions with other electronegative atoms
Why are hydrogen bonds so important?
They help hold molecules together like water and DNA — without hydrogen bonds, water would not flow through anything
What are the properties of water?
Cohesion, adhesion and surface tension
What is cohesion?
The attractive force between water molecules that help them pull together (chain link)
What is adhesion?
Water sticks to anything with a charge (polar molecules) due to attractive forces
Surface tension
How difficult it is to break or stretch the surface of a liquid — takes a LOT of energy
Why does water resist temperature change?
Hydrogen bonds must break first for water’s temperature to change, and that process takes a lot of energy.
Heat
The amount of energy associated with the motion of atoms and molecules
Temperature
The average speed of molecules and the heats intensity
Evaporative cooling
When water evaporates and releases heat leaving something cold (think about sweat)
Why is ice less dense than water?
When water freezes, the hydrogen bonds spread apart and create a less-compact system
What is a solvent?
Something that dissolves things
What is a solute?
The substance being dissolved
What is a solution?
What is created when a substance is dissolved
What is an aqueous solution?
When water is the solvent
Why does water dissolve so many things?
Its polarity — it is naturally attracted to things with charges and can pull them apart in the process
What will water NOT adhere to?
Fats, oils — anything nonpolar
How do water molecules dissolve things?
The positive end of water molecules (hydrogen) surround the negative end of the solute while the negative end of water molecules (oxygen) surround the positive side of the solute
The solute is separated and dissolved
What happens in aqueous solutions?
Water molecules break apart and form ions
What are the two ions formed in aqueous solutions
Hydrogen and hydroxide
What is an acid?
A substance that produces hydrogen ions and donates them
What is a base?
A substance that accepts hydrogen ions and produces hydroxide ions
What is the pH scale?
The measure of how acidic or basic a solution is
How is the pH scale organized?
(0-6) Acidic : High hydrogen
(7) Neutral
(8-14) Basic : Less hydrogen, more hydroxide