Chapter 1: Atoms Flashcards
Matter
Anything that occupies space and has mass. It is composed of particles and the structure of those particles determines the properties of matter.
States of Matter
A classification of a form of matter as a solid, liquid, or gas.
Solid
Atoms or molecules are packed close to one another in fixed locations.
- definite volume
- rigid shape
Liquid
Atoms or molecules pack about as closely as they do in solid mater but are free to move relative to each other.
- fixed volume
- no fixed shape
Gas
Atoms or molecules have a lot of space between them and are free to move relative to one another.
- Lacks a definite shape and volume
- Conforms to the shape and volume of its container
Composition of Matter
Refers to the types of particles that compose it.
- pure substances or mixtures (heterogeneous or homogeneous mixtures)
Pure Substances
Are composed of only one type of atom or molecule. Can be an element or a compound.
Element
A substance that cannot be chemically broken down into a less complex substance.
Compound
A substance composed of two or more molecules in fixed, definite proportions.
Mixtures
Substances composed of two or more different types of atoms or molecules that can be combined in variable proportions.
Heterogeneous Mixture
The composition varies from one region to another.
Homogeneous Mixture
The composition remains the same throughout it.
Law
A brief statement or equation that summarizes past observations and predicts future ones.
Law of Conservation of Mass
Matter is neither created nor destroyed in a chemical reaction.
Theory
A proposed explanation for observations and laws.
- based on well established and tested hypotheses
- predicts behavior beyond the observations and laws on which it was based
The Law of Definite Proportions (aka The Law of Constant Composition)
All samples of a given compound, regardless of their source or how they were prepared, have the same proportions of their constituent elements. This allows mass ratio to be found.
Mass Ratio
To find divide the larger mass by the smaller one.
The Law of Multiple Proportions
When two elements (A and B) form two different compounds, the masses of element B that combine with one gram of element A can be expressed as a ratio of small whole numbers.
Mass Number (A)
The molecular weight on the periodic table rounded to the nearest whole number. Can be found by taking the sum of the number of protons and neutrons in an atom.
Atomic Number (Z)
Number of protons in an element. The atomic number defines the element.
Periodic Table
A table that arranges all known elements in order of increasing atomic number. Elements with similar properties generally fall into columns.
Chemical Symbol
A one or two letter abbreviation for an element that is listed directly below its atomic number on the periodic table.
Isotopes
One of two or more atoms of the same element with the same number of protons but different numbers of neutrons and therefore different masses.
Natural Abundance
The relative percentage of a particular isotope in a naturally occurring sample with respect to other isotopes of the same element.
