Science

• Thales believed it was water because water is found everywhere.
• Anaximenes believed it was air because air is always in motion.
• Heraclitus believed it was fire because fire represented the changing world.
• Aristotle contradicted the idea of a primal matter and proposed that all substances are composed of four elements: air, earth, water, and fire.
• Democritus and his teacher Leucippus presented a remarkable idea about the nature of matter.
• They thought that all things are composed of tiny bits of matter, that cannot be further divided.
• Democritus and Leucippus called each indivisible piece atom (which means "Indivisible").
• The four basic principles of the particle nature of matter are: Matter is made up of discrete particles, There is empty space between the particles, The particles are in constant motion, and Forces act between the particles.
• Matter is composed of discrete particles.
• There is empty space between the particles of matter.
• The particles of matter are in constant motion.
• Forces act between the particles of matter.
• Liquids flow because their particles slide past one another.
• Gases are compressible because their particles are far apart.
• Solids are the densest among the three states of matter because they have the strongest attractive force between particles.
• If a substance is cooled, its particles will move closer together.
• When water changes state from liquid into gas, the water particles move faster and farther away from one another.
• The basic principle of the particle nature of matter is that matter is composed of discrete particles.
• The kinetic energy of gases is greater than that of liquids and solids because gases have weaker attractive forces between their particles, allowing them to move more freely and have higher velocities.