Chapter 1 Flashcards
Matter
anything that occupies space and has mass.
Atoms
the basic particles that compose ordinary matter
molecules
Atoms often bound together in specific geometrical arrangements
Structure of molecules
Determines properties of molecule
substance
A specific instance of matter—such as air, water, or sand
state
The first classification of matter
Composition
The second classification of matter
A pure substance
made up of only one type of particle (one component), and its composition is invariant (it does not vary from one sample to another)
A mixture
a substance composed of two or more particles in proportions that can vary from one sample to another
element
a substance that cannot be chemically broken down into simpler substances.
compound
substance composed of two or more elements (in this case hydrogen and oxygen) in fixed, definite proportions
heterogeneous mixture
one in which the composition varies from one region of the mixture to another—the different particles that compose water and sand do not mix uniformly.
homogeneous mixture
one with the same composition throughout—the particles that compose sweetened tea mix uniformly.
hypothesis
a tentative interpretation or explanation of the observations
scientific law
a series of similar observations
law of conservation of mass
Matter is neither created nor destroyed
theory
One or more well-established hypotheses
Law of Conservation of Mass
In a chemical reaction, matter is neither created nor destroyed.
chemical reaction
a process in which one or more substances are converted into one or more different substances.
law of definite proportions
All samples of a given compound, regardless of their source or how they were prepared, have the same proportions of their constituent elements.
Law of Multiple Proportions
When two elements (call them A and B) form two different compounds, the masses of element B that combine with 1 g of element A can be expressed as a ratio of small whole numbers.
John Dalton and the Atomic Theory
1) Each element is composed of tiny, indestructible particles called atoms.
2) All atoms of a given element have the same mass and other properties that distinguish them from the atoms of other elements.
3) Atoms combine in simple, whole-number ratios to form compounds.
4) Atoms of one element cannot change into atoms of another element. In a chemical reaction, atoms only change the way that they are bound together with other atoms.
J. J. Thomson
Used cathode rays to find charge-to-mass ratio of the cathode ray particles by deflecting them using electric and magnetic fields
What did J.J Thomson discover
He discovered the electron
Robert Millikan
deduced the charge of a single electron
What did J.J Thomson propose?
The plum-pudding model: negatively charged electrons were small particles held within a positively charged sphere.
radioactivity
he emission of small energetic particles from the core of certain unstable atoms
Rutherford’s Gold Foil Experiment
Disproved the plum-pudding model and proposed the nuclear theory.
Nuclear theory
1) Most of the atom’s mass and all of its positive charge are contained in a small core called the nucleus.
2) Most of the volume of the atom is empty space, throughout which tiny, negatively charged electrons are dispersed.
3) There are as many negatively charged electrons outside the nucleus as there are positively charged particles (named protons) within the nucleus, so that the atom is electrically neutral.
James Chadwick
demonstrated that the previously unaccounted for mass of atom was due to neutrons
atomic number
The number of protons in an atom’s nucleus and is given the symbol Z
Isotopes
When the Number of Neutrons Varies
natural abundance
The abundance of isotopes of a chemical element as naturally found on a planet
mass number
The sum of the number of neutrons and protons in an atom and is represented by the symbol A:
Ions
Losing and Gaining Electrons
Atomic mass
the mass of an atom of a chemical element expressed in atomic mass units
mass spectrometry
a technique that separates particles according to their mass.
