Lecture 2 - Essential Chemistry for Biology Flashcards
What is Matter?
anything that occupies space and mass
Element?
substance that cannot be broken down into other substances by chemical reactions.
How many naturally occurring elements on Earth?
92
How many elements are essential to the human body?
25
Oxygen, carbon, hydrogen, and nitrogen make up what percentage of the body?
96%
What are Trace Elements?
- elements that are required in only very small amounts
- Essential for life
Atom
Smallest unit of matter that still retains the property of an element.
Protons
Positive charge in the nucleus.
Neutrons
(no charge): in the nucleus
Electrons
(negative charge): orbit the nucleus
Atomic number
Number of protons determine what element it is
Mass
measure of amount of material in an object
Mass number
is the sum of the number of protons and neutrons in its nucleus.
Isotopes
- alternate mass forms of an element
- same number of protons
- same number of electrons
- But different number of neutrons
compounds
substances that contain two or more elements in a fixed ratio
What determines the the element of an atom?
Protons
Charged atoms are called what?
Ion
How are ionic bonds formed?
formed between oppositely charged ions
What happens in Ionic bonds?
a transfer of electrons bonds atoms together
When does a covalent bond form?
forms when two atoms share one or more pairs of
outer-shell electrons.
out of all the various bonds, which are the strongest?
Covalent bonds
what is a Molecule?
two or more atoms held together by covalent bonds
Polar molecule?
- an uneven distribution of charge
- Electrons in its covalent bonds are not shared equally
Is water Polar?
Yes
What are weak attractions called?
Hydrogen bonds
The polarity of water results in _______?
weak electrical attractions between neighboring water molecules.
How do cells constantly rearrange molecules?
by breaking existing chemical bonds and forming new ones
Chemical reaction?
changes in the chemical composition of matter
reactants?
starting materials
products
end materials
cells are composed of what % of water
70-95%
What are the properties of water?
- )water’s cohesive nature
- )water’s ability to moderate temperature
- ) Ice Floats
- )the Solvent of life
Cohesion?
tendency of molecules of the same kind to stick together
surface tension
measure of how difficult it is stretch or break the surface of a liquid
Hydrogen bonds give water an usually ___ surface tension
High
Heat?
amount of energy
associated with the movement
of the atoms and molecules in
a body of matter.
Temperature?
measures the
intensity of heat (the average
speed of the molecules).
Why does ice float?
it is less dense than liquid water
Evaporating cooling occurs when?
a substance evaporates and the surface of the liquid remaining behinds cools down.
Solution?
liquid consisting of a homogenous mixture of two or more substances.
Solvent
dissolving agent
solute
dissolved agent
Aqueous solution?
When water is the solvent, the result is an aqueous solution
Acid?
a chemical compound that releases H+ ions when placed in water
Base?
a compound that accepts H+ ions (removes them from the solution) when placed in water.
pH scale?
describes the acidity of a solution
The reactive properties (chemical behavior) of an atom
mostly depend on the number of
electrons in the outer electron shell of the atom.
Water molecules form hydrogen bonds because
the water molecule
is polar.
