All Matter Is Made of Elements, but Most Elements in Nature Are Found Combined with Other

Compounds

All matter is made of elements, but most elements in nature are found combined with other elements. A ______is a pure substance made of two or more ______chemically combined in a set ratio.

A compound may be represented by a chemical ______, which shows the elements in the compound and the ratio of atoms. For example, part of the gas you exhale is carbon dioxide. Its chemical formula is ______. The number 2 below the symbol for oxygen tells you that the ratio of carbon to oxygen is 1 to 2. (If there is no number after the element’s symbol, the number 1 is understood.)

If a different ratio of carbon atoms and oxygen atoms are seen in a formula, you have different compound. For example, carbon monoxide—a gas produced in car engines—has the formula ______. Here, the ratio of carbon atoms to oxygen atoms is 1 to 1.

When elements are chemically combined, they form ______having properties that are different from those of the uncombined ______.

Look at the following table:

Compound / Element #1 of compound / Element #2 of compound / Element #3 of compound
C12H22O11
Properties of compound / Properties of that element / Properties of that element / Properties of that element
Phase at room temperature:
Color:
Density: 1.587 g/cm3 / Phase at room temperature:
Color:
Density: 2.09 g/cm3 / Phase at room temperature:
Color:
Density: 0.00131 g/cm3 / Phase at room temperature:
Color:
Density: 0.0000899 g/cm3
Compound / Element #1 of compound / Element #2 of compound / Element #3 of compound
H3PO4
Properties of compound / Properties of that element / Properties of that element / Properties of that element
Phase at room temperature:
Color:
Density: 1.685 g/cm3
Other: / Phase at room temperature:
Color:
Density:
1.8 (White Phosphorus)
2.2 (Red Phosphorus)
Other: / Phase at room temperature:
Color:
Density: 0.00131 g/cm3
Other: / Phase at room temperature:
Color:
Density: 0.0000899 g/cm3
Other:
Compound / Element #1 of compound / Element #2 of compound
H2O2
Properties of compound / Properties of that element / Properties of that element
Phase at room temperature:
Color:
Density: 1.44 g/cm3
Other: / Phase at room temperature:
Color:
Density: 0.0000899 g/cm3
Other: / Phase at room temperature:
Color:
Density: 0.00131 g/cm3
Other: