Ch.2 The Chemical context of life Flashcards
Matter
is anything that takes up space and has mass.
Matter is made up of elements
Matter in combinations is called?
Compounds
Element
is a substance that cannot be broken down to other substances by chemical reactions
Compound
is a substance consisting of two or more elements in a fixed ratio
A compound has emergent properties, characteristics different from those of its elements
Essential Elements
Of 92 natural elements,
about
20–25% are essential elements, needed by an organism to live a healthy life and reproduce
Humans need 25 elements
plants need only 17
Trace Elements
Are elements that a living organism needs but a very small amount.
Trace Elements are required in only minute quantities
For example, in vertebrates, iodine (I) is required for normal activity of the thyroid gland
In humans, an iodine deficiency can cause goiter
What are the four elements that make up 96.3% of living matter?
What elements make up the other 3.7%?
who is CHON (96.3%)
C = Carbon
H = Hydrogen
O = Oxygen
N = Nitrogen
Hes the KCaPS of the orientals (3.7%)
K = Potassium
Ca = Calcium
P = Phosphorus
S = Sulfur
What is an Atom?
What three subatomic particles make up an atom?
An Atom is the smallest unit of matter that still retains the properties of an element.
Smallest particle of an element that retains its properties.
The three particles that make up an atom are called subatomic particles.
- Neutrons (neutral)
- Protons (positive)
- Electrons (negative)
atoms have a nucleus
electrons and protons attract each other so atoms usually have the same number of protons and electrons
Atomic nucleus is? (what type of charges) and where is the nucleus located in an Atom?
What surrounds the Atoms nucleus and why?
An Atoms nucleus is in the center of the atom, its also a combinaton of Protons and Neutrons that are packed together tightly in a dense core.
The atoms nucleus is a positive charge.
Surrounding the atoms nucleus is rapidly moving electrons that form a “cloud” the cloud is negatively charged. since protons and electrons are attracted to one another, the electrons stay in the vicinity of the nucleus.
Dalton is used to measure what?
Atoms, subatomic particles and molecules.
Neutrons and protons equal 1 Dalton
Same as atomic mass unit, or amu.
what is an Atomic number
the number of protons in one atom of an element.
is written a subscript to the left of the symbol for the element.
What is a mass number? what is the equation to find the mass number.
a combination of protons and neutrons in an atom
mass number = protons + neutrons
Atomic Mass
Mass of an Atom, which is a combination of its protons and neutrons.
the average mass number of an elements atom and its isotopes.
How do you get the number of neutrons of an element?
Mass number - atomic number
What are Isotopes?
A variation of an element. it contains a different number of protons than neutrons.
What is a radioactive isotope?
What are some uses of radioactive isotopes in biological research?
When the nucleues decays spontaneously, giving off particles and energy
When and element decays it turns into another element
example,
14C decays it becomes an atom of Nitrogen
Some applications of radioactive isotopes in biological research are
- Dating fossils
- Tracing atoms through metabolic processes
- Diagnosing medical disorders
What is energy (dealing with elements and atoms)
The capacity to cause change-for instance, by doing work.
What is Potential energy? give an example
The energy that matter possesses because of its location or structure.
energy of position further away from its resting state.
The electrons of an atom have potential energy due to their distance from the nucleus
Changes in potential energy occur in steps of fixed amounts
An electron’s energy level is correlated with its average distance from the nucleus
Example, water in a reservoir on a hill has potential energy because of its location or structure.
What are electron shells?
Electrons are found in different electron shells, each with a characteristic average distance from the nucleus
The energy level of each shell increases with distance from the nucleus
Electrons can move to higher or lower shells by absorbing or releasing energy, respectively
What is the chemical behavior of and atom determined by?
The chemical behavior of an atom is determined by the distribution of electrons in electron shells
What are Valence electrons and whats the name of the shell they are in?
are the electrons in the outermost shell and the name of that shell is the valence shell.
Elements with an incomplete valence shell are more likely to have chemical behavior.
if the valence shell is complete (full) the element is inert(chemicaly unreactive).
The reactivity of an atom arises from the presence of one or more unpaired electrons in the valence shell
Atoms with completed valence shells are unreactive, or inert
What are chemical bonds?
What are the strongest kinds of chemical bonds?
When two or more atoms combine together because of their velence shell not being full.
The strongest kinds of chemical bonds a are covalent bonds and ionic bonds.
What is a covalent bond?
The sharing of a pair of valence electrons by two atoms.
In a covalent bond, the shared electrons count as part of each atom’s valence shell
Two or more atoms held together by covalent bonds constitute a molecule
What is a molecule
When two or more atoms are held together by covalent bonds.
Single bond
the sharing of one pair of electrons, is indicated by a single line between the atoms
For example, H—H
Double bond
A double bond, the sharing of two pairs of electrons, is indicated by a double line between atoms
For example,
valence
Each atom that can share valence electrons has a bonding capacity, the number of bonds that the atom can form
Bonding capacity, or valence, usually corresponds to the number of electrons required to complete the atom
What is electronegativity?
the attraction of a particular atom for the electrons of a covalent bond.
The more electronegative an atom, the more strongly it pulls shared electrons toward itself
nonpolar covalent bond
the atoms share the electrons equally
Nonpolar covalent bonds, with equal sharing of the bond electrons, arise when the electronegativities of the two or more atoms are equal.
All equal strength nigs trying to get the money
Polar covalent bond
The greater the electronegativity difference, the more ionic the bond is. Bonds that are partly ionic are calledpolar covalent bonds
When the big nig over powers the two little nigs and takes there money.
What are Ions?
an atom or molecule with a net electric charge due to the loss or gain of one or more electrons.
What is a Ionic bond?
What is a cation and an anion?
What do the two have to do with one another with bonding?
is an attraction between an anion and a cation
A positively charged Ion. +1
A negatively charged Ion. -1
A Cation and a Anion atract one another because a cation is a positively charged ion and an Anion is a negatively charged ion.
The two opposites attract.
Ionic Compounds
Compounds formed by ionic bonds are called ionic Compounds
or Salts.
What is the difference between Ionic compound and Covalent compound?
Ionic compound is when two or more charged elements are attracted to one another. metal and non-metals
covalent when to or more elements eletrons are shared between their orbitals. creating bonds.
What are the majority of strongest bonds in organisms? and what do they form?
covalent bonds, they form cell molecules
List the 3 weak chemical bonds
Ionic bonds, hydrogen bonds, and van der waals interactions
What is a hydrogen bond?
A hydrogen bond is the electrostatic attraction between two polar groups that occurs when a hydrogen (H) atom covalently bound to a highly electronegative atom such as nitrogen (N), oxygen (O), or fluorine (F)
When a hydrogen of from one molecule is attracted to a Nitrogen Oxygen or Fluorine from another molecule creating a HYDROGEN BOND (Attraction)
Van Der Waals Interactions
An Attraction the positive part of one molecule to the negative part of an another.
Why is the molecular shape of a molecule important in biology
A molecule’s shape is key to its function in the cell
Molecular shape determines how biological molecules recognize and respond to one another
What are chemical reactions?
The making and breaking of chemical bonds, leading to changes in composition of matter.
reactants
The starting molecules of a chemical reaction
Products
The final molecules of a chemical reaction
Chemical Equilibrium
When the rates of the foward (reactant to product) and reverse (product to reactant) are happening at the same speed.
Polar Molecule
The unequal sharing of electrons and waters v like shape make it a polar molecule.
Overall charge is unevenly distributed.
What Four emergent properties of water contribute to Earth’s suitability for life:
- Cohesive behavior
- Ability to moderate temperature
- Expansion upon freezing
- Versatility as a solvent
What is Cohesion?
Water molecules are linked by multiple hydrogen bonds
The molecules stay close together
What is Adhesion?
the clinging of one substance to another, also plays a role
Surface tension
is a measure of how hard it is to break the surface of a liquid
Surface tension is related to cohesion
Kinetic energy
is the energy of motion
Thermal energy
Is a measure of the total amount of kinetic energy due to molecular motion
Heat
Thermal energy in transfer from one body of matter to another is defined as heat
calorie (cal)
is the amount of heat required to raise the temperature of 1 g of water by 1°C
kilocalories (kcal),
The “calories” on food packages are actually kilocalories (kcal), where 1 kcal = 1,000 cal
joule (J)
is another unit of energy, where
1 J = 0.239 cal, or 1 cal = 4.184 J
Specific heat
The specific heat of a substance is the amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1°C
The specific heat of water is 1 cal/(g × °C)
Water resists changing its temperature because of its high specific heat
What can waters high specific heat be traced to and why?
Water’s high specific heat can be traced to hydrogen bonding
Heat is absorbed when hydrogen bonds break
Heat is released when hydrogen bonds form
The high specific heat of water keeps temperature fluctuations within limits that permit life
Heat of vaporization
Is the heat a liquid must absorb for 1 g to be converted to gas
Evaporative cooling
As a liquid evaporates, its remaining surface cools, a process called evaporative cooling
Evaporative cooling of water helps stabilize temperatures in bodies or water and organisms
Why does ice float in liquid water?
Ice floats in liquid water because hydrogen bonds in ice are more “ordered,” making ice less dense
Water reaches its greatest density at 4°C
If ice sank, all bodies of water would eventually freeze solid, making life impossible on Earth
aqueous solution
is one in which water is the solvent
hydration shell
Water is a versatile solvent due to its polarity, which allows it to form hydrogen bonds easily
When an ionic compound is dissolved in water, each ion is surrounded by a sphere of water molecules called a hydration shell
What is the difference between hydrophilic and Hydrophobic?
A hydrophilic substance is one that has an affinity for water
A hydrophobic substance is one that does not have an affinity for water
Oil molecules are hydrophobic because they have relatively nonpolar covalent bonds
Molecular mass
the sum of all masses of all atoms in a molecule
1 mole represents?
Numbers of molecules are usually measured in moles, where 1 mole (mol) = 6.02 ´x 1023 molecules
Avogadro’s number and the unit dalton were defined such that 6.02 ´x 1023 daltons = 1 g
Buffers
are substances that minimize changes in concentrations of H+ and OH− in a solution
Most buffer solutions contain a weak acid and its corresponding base, which combine reversibly with H+
ocean acidification
Human activities such as burning fossil fuels threaten water quality
CO2 is a product of fossil fuel combustion
About 25% of human-generated CO2 is absorbed by the oceans
CO2 dissolved in seawater forms carbonic acid; this causes ocean acidification
Acid
When an acid dissolves in water it donates and H+
An acid is a substance that increases the hydrogen ion concentration of a soulution.
example,
A strong acid like hydrochloric acid, HCl, dissociates completely into H+ and Cl− in water:
HCl → H+ + Cl−
This source of H+ (dissociation of water is the other source) results in an acidic solution one having more H+ than OH–
Base
A base reduces the concentration of H+
by taking the H+
Some bases reduce the H+ concentration directly by accepting hydrogen ions.
Ammonia (NH3) for instance, acts as a base when the unshared electron pair in nitrogens valence shell attracts hydrogen ion from the solution, resulting in an ammonium ion (NH4+)
Other bases reduce the H+ concentration indirectly by dissociating to form hydroxide ions, which combine with hydrogen ions and form water. one such base is sodium hydroxide (NaOH)
