A Study of Matter

Phases of Matter

All matter is made from atoms. Every substance (oxygen, lead, silver, neon ...) has a unique number of protons, neutrons, and electrons. Oxygen, for example, has 8 protons, 8 neutrons, and 8 electrons. Hydrogen has 1 proton and 1 electron. Individual atoms can combine with other atoms to form molecules.

Definition

Water molecules contain two atoms of hydrogen H and one atom of oxygen O and is chemically called H2O. Oxygen and nitrogen are the major components of air and occur in nature as diatomic (two atom) molecules. Regardless of the type of molecule, matter normally exists as either a solid, a liquid, or a gas. We call this property of matter the phase of the matter. The three normal phases of matter have unique characteristics which are listed on the slide.

Multiple Choice

Matter is made from ____

• Atom

• Particles

• Dust

Solid

In the solid phase the molecules are closely bound to one another by molecular forces. A solid holds its shape and thevolume of a solid is fixed by the shape of the solid.

Liquid

In the liquid phase the molecular forces are weaker than in a solid. A liquid will take the shape of its container with a free surface in a gravitational field. In microgravity, a liquid forms a ball inside a free surface. Regardless of gravity, a liquid has a fixed volume.

Gas

In the gas phase the molecular forces are very weak. A gas fills its container, taking both the shape and the volume of the container.

Plasma

The three normal phases of matter listed on the slide have been known for many years and studied in physics and chemistry classes. In recent times, we have begun to study matter at the very high temperatures and pressures which typically occur on the Sun, or during re-entry from space.

Multiple Select

What is true about solid?

• It will take the shape of its container

• the molecules are closely bound to one another by molecular forces

• fills its container, taking both the shape and the volume of the container.

• It holds its shape and the volume