Section 1 Matter and Thermal Energy Essential Questions

Section 1 Matter and Thermal Energy

Essential Questions What is the kinetic theory of matter? How do particles move in the different states of matter? How do particles behave at the boiling and melting points?

Review Vocabulary kinetic energy : energy of motion

New Vocabulary kinetic theory sublimation melting point plasma heat of fusion thermal expansion boiling point heat of vaporization

The kinetic theory , also known as kinetic molecular theory, is an explanation of how the particles in gases behave. To explain the behavior of particles, it is necessary to make some basic assumptions. The assumptions of the kinetic theory are as follows: 1. All matter is composed of tiny particles (atoms, molecules, and ions). 2. These particles are in constant, random motion. 3. The particles collide with each other and with the walls of any container in which they are held. 4. The amount of energy that the particles lose from these collisions is negligible. Dana Hoff/Getty Images Kinetic Theory

The particles that make up the water are moving fast and colliding with the particles that make up the ice cube. Those collisions transfer energy from the water to the ice. The particles at the surface of the ice cube vibrate faster, transferring energy to other particles in the ice cube. © 81 a/age fotostock Changes of State

Plasma State So far, you have learned about the three familiar states of matter—solids, liquids, and gases. However, there is a state of matter beyond the gas state. Plasma is matter that has enough energy to overcome not just the attractive forces between its particles but also the attractive forces within its atoms. The atoms that make up a plasma collide with such force that the electrons are completely stripped off the atoms. You may be surprised to learn that most of the ordinary matter in the universe is in the plasma state. Every star that you can see in the sky, including the Sun, is composed of matter in the plasma state. Most of the matter between the stars and galaxies is also in the plasma state. The familiar states of matter—solid, liquid, and gas—are extremely rare

Recall that particles move faster and farther apart as the temperature rises. This separation of particles results in an expansion of the entire object, known as thermal expansion. Thermal expansion is an increase in the size of a substance when the temperature is increased. Substances also contract when they cool. Burke/Triolo/Brand X Pictures/Jupiterimages Thermal Expansion

Some solids are like butter. Instead of having a specific melting point, they soften and gradually turn into a liquid over a temperature range. These solids lack a crystalline structure and are called amorphous solids. One common amorphous solid is glass, shown at the right. Martin Child/Getty Images Solid or Liquid?

Liquid crystals form another group of materials that do not change states in the usual manner. Normally, the ordered geometric arrangement of a solid is lost when the substance goes from the solid state to the liquid state. Liquid crystals start to flow during the melting phase, similar to a liquid. But they do not lose their ordered arrangement completely, as most substances do. Liquid crystals will retain their geometric order in specific directions. Many small computing devices and electronics, such as MP 3 players, cell phones, TVs, and netbooks, utilize liquid crystal displays (LCDs). Matt Meadows/Mc. Graw-Hill Education Solid or Liquid?

Assessment 1. At what temperature is the pressure of the vapor in a liquid equal to the external pressure on that liquid? A absolute zero B boiling point C melting point D heat of fusion CORRECT

Assessment 2. What is the most common state of matter in the universe? A solid B gas C liquid D plasma CORRECT

Assessment 3. What is the amount of energy needed to change a solid to a liquid at its melting point? A heat of fusion B temperature C heat of vaporization D absolute zero CORRECT