Chapter 2 (Exam One) Flashcards
Matter?
refers to anything that has mass and occupies space.
Matter exists in three states:
solid, liquid, gas
All matter (both living and non-living) is composed of?
Basic substances called elements
A element is?
a substance that cannot be broken down into substances with different properties; composed of one type of atom.
How many elements are naturally occurring?
92
6 elements makeup 95% of the body weight of organisms, what are they?
(CHNOPS) Carbon Hydrogen Nitrogen Oxygen Phosphorus Sulfer
A atom is?
the smallest part of an element that displays the property of the element.
A atom is composed of?
Protons, neutrons, electrons, and a central nucleus
proton?
Positively charged, 1 amu
Neutron?
No charge, 1 amu
Electron?
Negatively charged, very low mass-negligible in calculations
Electron shells?
Orbiting clouds around the nucleus
Each element is represented by?
One or two letters to give it a unique s=ymbol
H?
Hydrogen
Na?
Sodium
C?
Carbon
The atomic number is?
Equal to the number of protons in each atom of an element
The mass number? Atomic mass
Of an atom is equal to the sum of the number of protons and neutrons in atoms nucleus
The atomic mass?
Is approximately equal to the mass number
Periods?
Atoms of an element arranged horizontally by increasing atomic number in rows
Groups?
Atoms of an element arranged in vertical columns
Atoms shown in the the periodic table are?
Electrically neutral
The atom number tell you’d the number of ______ as well as the number of _____?
Electrons, protons
Isotopes?
Are atoms of the same element that differ in the number of neutrons (and therefore different atomic masses.)
Some isotopes spontaneously?
Decay
Radioactive isotopes?
Give off energy in the form of rays and subatomic particles
Carbon 14 is an example of? What’s is been used for?
A radioactive isotope; been used to examine reactions in photosynthesis
Isotopes can be?
Helpful or harmful
Electrons are attracted to?
The positively charged nucleus; thus it takes energetically to hold electrons in place
What does it take to push elections away?
It takes energy to push them away and keep them in their own shell
The more distant the shell?
The more energy it takes to hold in place
Elections determine?
Chemical behavior of atoms
Bohr model?
Is a useful way to visualize electron location
Another word for Energy levels?
Energy shells
Electrons revolve around? In what form?
The nucleus; in energy shells
The following rules apply for atoms with atomic numbers of 20 or less?
- The first energy shell can hold up to 2 electrons
- Each additional shell can hold up to 8 electrons
- Each lower shell is filled first before electrons are placed in the next shell
Valence shell?
The outermost energy shell of any atom
The valence shell is important because?
It determines many of an atoms chemical properties
Octet rule?
What’s the one exception?
States that the outermost shell is most stable when it has 8 electrons
Exception: if an atom has only one shell, the outermost valence shell is complete when it has two electrons
Chemical reaction?
The process of bond formation
Ion?
Is an atom that has lost or gained an electron
Ionic bond? Example
Forms when electrons are transferred from one atom to another atoms and the oppositely charged ions are attracted to each other
Formation of sodium chloride
Salts?
Are solid substances that usually separate and exist as individual ions in water
Covalent bonds?
Result when two atoms share electrons so each atom has an octet of electrons in the outer shell
Nonpolar covalent bond? Examples
Electrons are shared equally between atoms
Hydrogen gas, oxygen gas, methane
Polar covalent bond? Example?
Electrons are shared unequally
Water
Electronegativity?
Is the ability of an atom to attract electrons towards itself in a chemical bond
Water is a?
Polar molecule
Hydrogen bond?
Is a weak attraction between a slightly positive hydrogen atom and a slightly negative atom
Water molecules cling together because of?
Hydrogen bonding
_____ has a high heat capacity?
Water
The presence of many hydrogen bonds allow?
Water or absorb a large amount of thermal energy without a great change in temperature
The temperature of water?
Rises and falls slowly
Water has a high heat of?
Evaporation
Hydrogen bonds must be?
Broken to evaporate water
Bodies of organisms?
Cool when their heat is used to evaporate water
Water is a good?
Solvent
Why is water a good solvent?
Because of its polarity
Polar substances?
Dissolve readily in water
Hydrophilic?
Molecules dissolve in water
Hydrophobic?
Molecules do not dissolve in water
Solution?
Contain dissolved substances or solutes
Water molecules are?
Cohesive and adhesive
Cohesion?
Is the ability of water molecules to cling to each other due to hydrogen bonding
- water flows freely
- surface tension
Adhesion?
Is the ability of water molecules to cling to other polar surfaces
- due to waters polarity
- capillary action
Cohesion and adhesion account for?
Water transport in plants as well as transport in blood vessels
Frozen water (ice) is?
Less dense than liquid water
Water expands as it?
Reaches 0c and freezes
Ice floats? It acts as what while doing this?
On liquid water ; acts like an insulator on top of a frozen body of water
pH?
Is a measure of hydrogen ion concentration in a solution
When water ionizes and dissociate, it?
Releases an equal number of hydrogen (H+) ions and hydroxide (OH-) ions
Acids?
Are substances that dissociate in water releasing hydrogen ions
Bases?
Are substances that either take up hydrogen ions or release hydroxide ions
pH scale?
Is used to indicate the acidity or basicity (alkalinity) of a solution
0 to <7 =
Acidic
7 =
Neutral
> 7 to 14 =
Basic (or alkaline)
Logarithmic scale?
Each unit change in pH represents a 10-fold change in H+ concentration
Buffer?
Is a chemical or a combination of chemicals that keeps pH within normal limits
Human blood is normally pH?
7.4 (slightly basic)
Acidosis?
If blood pH drops below 7.0
Alkalosis?
If blood pH rises above 7.8
An element and atom share what?
the same name
Atoms within the same group share what?
the same chemical binding characteristics
Electrons have energy due to what? What’s the energy called?
Relative position; potential energy
The number of electrons in an atom’s valence shell determines what?
Whether the atom gives up, accepts, or shares electrons to acquire eight electrons in the outer shell
Atoms that have their valence shells filled with electrons tend to what?
Be chemically stable
Atoms that do not have their valence shells filled with electrons are what?
Chemically reactive
A molecule is what?
Two or more elements bonded together. Smallest part of a compound that retains its chemical properties
A compound is what?
A molecule containing at least two different elements bonded together.
A formula tells what
The number of each kind of atom in a molecule
Bonds that exist between atoms in molecules contain what?
Energy
Bonds between atoms are caused by what?
The interactions between electrons in outermost energy shells
What makes hydrogen bonding possible in water? What’s this an example of?
The shape of a water molecule and its polarity. Structure-function relationship
A hydrogen bond can occur between what?
Atoms of different molecules or with the same molecule
A single hydrogen bond is what while multiple hydrogen bonds are what
Weak; strong
A hydrogen bond helps to maintain what?
Proper structure and function of complex molecules such as proteins and DNA
The temp of water rises and falls slowly and this allows organisms to what?
Maintain their normal internal temperatures, protected from rapid temperature changes
At temperatures below what? Hydrogen bonds become what?
4 degrees Celsius. As they become more rigid but also more open
Body has built in mechanisms to prevent pH changes. Example?
Carbonic avid buffer dissociates and reforms to reduce changes in pH
