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Chapter 4
This is for the biology test.
25
Biology
9th Grade
09/06/2010

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Term

Matter

Definition
Anything that occupies space and has mass
Term
Element 
Definition

 pure substance that cannot be broken down into other substances by chemical or physical means

Term
Trace Element
Definition
element critical to health that makes up less than 0.01 percent of body mass
Term
Compound
Definition
substance containing two or more elements chemically combined in a fixed ratio
Term


 List the most common elements in living things.

 

Definition

 

 Gold, helium, mercury, and oxygen

 

Term

Compare and contrast elements and compounds.

Definition
  • An element is a pure substance that cannot be broken down into other substances by chemical means
  • A compound is a substance containing two or more elements that are chemically combined in a fixed ratio.
Term

Atom

Definition
smallest particle of an element
Term
Proton
Definition
subatomic particle with a single unit of positive electric charge (+)
Term
Neutron
Definition
subatomic particle that has no charge (is electrically neutral)
Term
Nucleus
Definition
in an atom, the central core that contains protons and neutrons; in a cell, the part that houses the cell's genetic material in the form of DNA
Term
Atomic number
Definition
number of protons in an atom's nucleus; is unique for each element
Term
isotope
Definition
one of several forms of an element, each containing the same number of protons in their atoms but a different number of neutrons
Term
radioactive isotope
Definition
isotope in which the nucleus decays (breaks down) over time, giving off radiation in the form of matter and energy
Term
Describe the structure of an atom.
Definition

The protons and neutrons are inside the nucleus and the electrons are outside. They formed a "cloud" of electrons.

[image]

Term

  Explain how isotopes can be used to study biological processes.

Definition
Radioactive isotopes are useful as "biological spies" for observing what happens to different atoms within organisms.
Term
Explain the role of an element's electrons in determining its chemical reactivity.
Definition

Electrons differ in the amount of energy they have and how tightly they are held by the protons in the nucleus. Based on these properties, chemists describe an atom's electrons as belonging to certain energy levels. Usually it is the electrons in the highest energy level of an atom that determine how that atom reacts.

Term
ionic bond
Definition
chemical bond that occurs when an atom transfers an electron to another atom
Term
ion
Definition
atom that has become electrically charged as a result of gaining or losing an electron
Term
covalent bond 
Definition
chemical bond that forms when two atoms share electrons
Term
molecule
Definition
two or more atoms held together by covalent bonds
Term
chemical reaction 
Definition
breaking of old and formation of new chemical bonds that result in new substances
Term
reactant 
Definition
starting material for a chemical reaction
Term
product
Definition
material created as a result of a chemical reaction
Term

 

Compare and contrast ionic bonds and covalent bonds.

 

Definition
  • Ionic bonds occurs when an atom transfers an electron to another atom.
  • Covalent bonds forms when two atoms share electrons.

[image]

Term
Summarize what happens in a chemical reaction.
Definition

 

  • Certain molecules constantly become rearranged into other molecules as existing chemical bonds break
  • One or more new substances are formed

 

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