bio test ch.2 part1

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the basic unit of matter is called an: atom
describe the nucleus of an atom: protons and neutrons are located in the nucleus and are binded by a strong force
protons have a _______ charge and are located in the ________.: positive;nucleus
neutrons have a _________ charge and are located in the _________.: neutral;nucleus
electrons have a __________ charge and are ___________ the nucleus.: negative;surround
why are atoms neutral despite having charged particles?: because atoms have equal numbers of electrons nad protons and because these subatomic particles have = but opposite charges, the atoms are neutral.
chemical element: pure substance that consists entirely of one type of atom.
what does an element's atomic number represent?: the number of protons in an atom of an element
isotopes: atoms of the same element that differ in the number of neutrons they contain.
isotopes are identified by: their mass number
why do all isotopes of an element have the same chemical properties?: they have the same number of electrons
chemical compound: substance formed by the chemical combo of 2 or more elements in definite properties.
what holds atoms in compounds together?: chemical bonds
covalent bond: electrons are shared between atoms
ionic bond: one or more electrons are transferred from one atom to another
ion: positively charged and negatively charged atom
an atom that loses electrons has a ________ charge.: positive
an atom that gains electrons has a ______ charge.: negative
the structure that results when atoms are joined by covalent bonds are called _______.: molecule
the slight attractions that develop between oppositely charged regins of nearby molecules are called _____________.: van der waals force
in a water molecule each hydrogen forms a _______ covalent bond.: single
atoms can share 6 electrons and form a _______ bond.: triple
matter has _______ and ________.: mass and volume
matter can be _________, ____________, or _________.: pure substances, chemical compounds, mixtures
matter may exist in three different states:: solid, liquid, gas
matter may also be ______________ or ____________ mixtures: homogenous, heterogeneous
are all matters visible? explain.: no, some may be odeorless and colorless gases
does matter take up space?: yes all matter has mass and volume
what is matter made of?: elemental atoms and chemical compounds
atom: an entity which cannot be divided furthur and still maintain its unique property
atoms are made up of _____________ particles.: subatomic
how are protons and neutrons bound to the nucleus?: by a strong force
some isotopes are __________ and _________.: unstable, radioactive
element: substance consisting entirely of one type of atom
what does it mean when an isotope is radioactive?: their nuclei are unstable and break down at a constant rate over time
are radioactive isotopes dangerous?: yes it can be dangerous but radioactive isotopes have a number of important scientific and practical uses
radioactive isotopes can be used to: treat cancer, to kill bacteria that causes food to spoil, and can be used as labels or â€œtracersâ€ to follow the movements of substances within organisms
Because isotopes the same number of electrons..: all isotopes of an element have the same chemical properties.
a chemical formula indicates the composition of a(an): compound
when atoms share four electrons, it forms a _______ bond.: double
Some atoms have a _______ attraction for electrons than do other atoms.: stronger
when a covalent bond begins to share electrons, the sharing is _______ equal.: not always
Even when the sharing of a covalent bond is equal, the rapid movement of electrons can create _______ on a molecule that have a tiny positive or negative charge.: regions
van der waals force: a slight attraction that develops between the oppositely charged regions of nearby molecules
a water molecule is _________.: neutral
what results from the oxygen atom being at one end of a water molecule and the hydrogen atoms being at the other end?: oxygen end: slight negative charge
hydrogen end: slight positive charge
why is a water molecule polar?: because there is an uneven distribution of electrons between the oxygen and hydrogen atoms.
_________ bonds are the strongest bonds that form between molecules.: hydrogen
cohesion attraction: an attraction between molecules of the same substance
adhesion: an attraction between molecules of different substances
why is water extremely cohesive: because of hydrogen bonding
the rise of water in a narrow tube against the force is called: a capillary action
how does capillary action affect plants?: because it draws water out of the root of the plants and up into its stems and leaves
what is a mixture?: material composed of 2 or more elements or compounds that are physically mixed together but not chemically combined
a mixture of two or more substances in which the molecules of the substances are evenly mixed is called a: solution
the greatest solvent in the world is: water
what is a suspension?: mixture of water and nondissolved materials
solute and example: substance that is dissolved in solvent to make a solution; tablesalt
solvent and example: substance in which solute dissolves; water
two water molecules react to form: ions
why is water neutral despite the production of hydrogen ions and hydroxide ions?: because the number of positive hydrogen ions produced is equal to the number of negative hydroxide ions produced.
what does the pH scale indicate?: if something is acidic, basic or neutral
what number is neutral on the pH scale?: 7 (water)
the more protons an atom has, the ________ the attraction is for electrons.: stronger
there is a greater probability of finding shared electrons near an atom with a ________ amount of protons an atom as: greater
Because of their partial positive and negative charges..: polar molecules such as water can attract each other
Hydrogen bonds are ______ strong as covalent or ionic bonds: not as
Water's cohesion causes molecules on the surface of water to be drawn _______, which is why drops of water form beads on a _______ surface: inward;smooth
Adhesion between water and glass also causes water to rise in a narrow tube against the force of gravity. what is this effect called?: a capillary action.
Cohesion and adhesion are similar in that: both are attractions between molecules.
all components of a ________, are evenly distributed.: solution
Water's ________ gives it the ability to dissolve both ionic compounds and other polar molecule: polarity
When an ionic compound such as sodium chloride is placed in water, water molecules _______ and ________ the positive and negative ions.: surround, separate
Some materials do not dissolve when placed in water but separate into pieces so small that they do not settle out. This is called ___________. give an example: suspensions; blood
the higher the pH the more ________ the solution: basic
the lower the pH the more _______ the solution: acidic
base: is a compound that produces hydroxide ions (OHâˆ’ ions) in solution
acid: is any compound that forms H+ ions in solution.
buffers: are weak acids or bases that can react with strong acids or bases to prevent sharp, sudden changes in pH
Controlling pH is important for maintaining __________.: homeostasis
A molecule in which the charges are unevenly distributed is called a: polar molecule
A dissolved substance is called a: solute
A compound that produces hydroxide ions in solution is called a: a base

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