Components of Matter
Chapter 2 The Components of Matter
Elements, Compounds, and Mixtures: An Atomic Overview
An element consists of only one kind of atom. An element is one kind of substance – the composition is fixed. Each element is unique because the properties of its atoms are unique. Molecules are structures containing two or more atoms chemically bound together. Diatomic molecules are two-atom molecules such as elemental oxygen.
A compound is a type of matter in which two or more different elements are chemically bonded – the elements are present in fixed parts by mass (fixed mass ratios) – therefore it is also considered a substance because the composition is fixed. Properties of a compound are different than those of its component elements.
A mixture is a group of two or more substances that are physically intermingled. They can very in their parts by mass, unlike compounds. They are not substances and retain the properties of their components. Can be separated by physical changes.
FUP2.1: Diatomic molecules undergo a chemical change into compounds (two different elements).
The Observations That Led to an Atomic View of Matter
Mass Conservation
Law of mass conservation states the total mass of substances do not change during a chemical reaction. The number of substances (and properties) may change, but the total amount of matter remains the same. Matter cannot be created nor destroyed.
Definite Composition
Law of definite (or constant) composition states that a compound is composed of the same elements in the same parts (fractions) by mass or the part of the compounds mass which contributes to the compound’s total mass. FUP2.2: 0.34t oxygen
Multiple Proportions
Law of multiple proportions: if elements A and B react to form two compounds, the different masses f B that combine with a fixed mass of A can be express as a ratio of small whole numbers.
Dalton’s Atomic Theory
Postulates of the Theory
1. All mater consists of atoms – indivisible particles which
Elements, Compounds, and Mixtures: An Atomic Overview
An element consists of only one kind of atom. An element is one kind of substance – the composition is fixed. Each element is unique because the properties of its atoms are unique. Molecules are structures containing two or more atoms chemically bound together. Diatomic molecules are two-atom molecules such as elemental oxygen.
A compound is a type of matter in which two or more different elements are chemically bonded – the elements are present in fixed parts by mass (fixed mass ratios) – therefore it is also considered a substance because the composition is fixed. Properties of a compound are different than those of its component elements.
A mixture is a group of two or more substances that are physically intermingled. They can very in their parts by mass, unlike compounds. They are not substances and retain the properties of their components. Can be separated by physical changes.
FUP2.1: Diatomic molecules undergo a chemical change into compounds (two different elements).
The Observations That Led to an Atomic View of Matter
Mass Conservation
Law of mass conservation states the total mass of substances do not change during a chemical reaction. The number of substances (and properties) may change, but the total amount of matter remains the same. Matter cannot be created nor destroyed.
Definite Composition
Law of definite (or constant) composition states that a compound is composed of the same elements in the same parts (fractions) by mass or the part of the compounds mass which contributes to the compound’s total mass. FUP2.2: 0.34t oxygen
Multiple Proportions
Law of multiple proportions: if elements A and B react to form two compounds, the different masses f B that combine with a fixed mass of A can be express as a ratio of small whole numbers.
Dalton’s Atomic Theory
Postulates of the Theory
1. All mater consists of atoms – indivisible particles which