States of Matter & Phase Changes

States of Matter Matter can be classified as solids, liquids, or gases based on whether their shapes and volumes are definite or variable. Kinetic theory of matter: all the particles of matter are in constant motion.

solids Has a definite shape and definite volume. Particles only slightly vibrate and are packed close together. Crystalline: particles are arranged in repeating 3D pattern called a crystal. Amorphous: particles are in a random arrangement.

Liquids Takes the shape of its container and has a definite volume. Molecules slide past each other.

Pascal’s Principle When a force is applied to a confined fluid any increase in pressure is transmitted equally to all parts of the fluid. The human heart has two force pumps.

Gases No definite shape of volume. Molecules move freely past each other.

Gas Pressure Pressure: unit is Pascal (Pa) Collisions between particles of a gas and the walls of the container cause the pressure in a closed container of gas. The more frequent the collisions, the greater the pressure of the gas is. The speed of the particle and their mass also affect the pressure.

Factors that affect Gas Pressure 1. Temperature: raising the temperature of a gas will increase its pressure if volume of the gas and the number of particles are constant. 2. volume: reducing the volume of a gas increases its pressure if the temperature of the gas and number of particles are constant. 3. number of particles: increasing the number of particles will increase the pressure of a gas if the temperature and the volume are constant.

Plasma Extremely high temperatures , such as those found on the sun or other stars, neon, fluorescent lights, and lightning bolts. Positive and negative charged particles. No definite shape or volume.

Physical Changes Some of the properties of the material change, but the substances in the material remain the same. Water from liquid to a gas during boiling Crumpling and slicing change size and shape. Some can be reversed (freezing and melting)

Phase Changes The reversible physical change that occurs when a substance changes from one state of matter to another.

Phase change graph

Energy and Phase Changes Energy is either absorbed or released during a phase change. Endothermic: the system absorbs energy from its surrounding. Melting Exothermic: the system releases energy to its surroundings. Freezing

Melting: at the m.p. of water 0°C some molecules gain enough energy to overcome their attraction and move from their fixed position . When all molecules have enough energy to move melting in complete. Freezing: at f.p. of water some molecules move slowly enough for the attraction between molecules to have an effect. When all molecules are drawn into an orderly arrangement freezing is complete.

Vaporization: when a substance changes from a liquid into a gas Vaporization: when a substance changes from a liquid into a gas. (endothermic) Evaporation: the process that changes a substance form a liquid to a gas at temperatures below the b.p.

Boiling: water at 100°C at sea level , some molecules below the surface of the liquid have enough kinetic energy to overcome the attraction of molecules. The water vapor is less dense than the liquid so rises. At surface they burst and release water vapor into the air.

Condensation: the phase change in which a substance changes from a gas or vapor into a liquid. Sublimation: is the phase change in which a substance changes from a solid to a gas. (endothermic) dry ice Deposition: when a gas or vapor changes directly into a solid without first changing to a liquid. (exothermic) frost hale