Matter, Mixtures, and Properties

Matter and Its Properties

• All matter has mass and volume.
• Energy cannot be created or destroyed, only changed.
• Light, heat, and sound are examples of things that exist but are not considered matter.

Substances and Mixtures

• A pure substance has a fixed composition.
• A mixture has a variable composition.
• Heterogeneous mixtures have visibly different components.
• Homogeneous mixtures have uniform composition.
  • Salad dressing is heterogeneous because particles are different sizes.
  • Salt water is homogeneous because particles are similar and dissolved.

Physical vs. Chemical Properties

• Density is a physical property used to identify a substance.
• Flammability is a chemical property that requires oxygen for testing.
• Reactivity describes how easily a substance combines with others.
  • Examples include chemical reactions like mixing vinegar and milk, or the dangerous reaction of windex and bleach, or mustard gas.
• A physical change alters a substance's appearance but not its composition.
• A chemical change results in a new substance with different characteristics.
  • Mixing vinegar and milk is a chemical change, producing a precipitate.
  • Ice melting is a physical change, as water remains water.

States of Matter

• Solids: Definite shape and volume.
• Liquids: Indefinite shape and definite volume.
• Gases: Indefinite shape and indefinite volume.

Kinetic Theory

• The kinetic theory explains that all matter is constantly in motion.
• Heating increases the motion of particles in matter.

Phase Changes

• Endothermic phase changes: Melting, vaporization, and sublimation.
• Exothermic phase changes: Freezing, condensation, and deposition.
• Sublimation: A direct change from solid to gas.
• Condensation: The phase change from gas to liquid.
  • Condensation occurs when a glass of ice tea is held, making the outside of the glass wet.

Phase Change Graphs

• The flat portions of phase change graphs represent phase changes.
• During phase changes energy is used for either separating or putting atoms together.
• The flat line is called melting when heating, and freezing when cooling a substance.

Gas Laws

• Factors affecting gas pressure (in a closed container): Volume, temperature, number of particles.

• Boyle's Law: Pressure and volume are inversely related.

• Charles' Law: Volume and temperature are directly related.

• Gay-Lussac's Law: Pressure and temperature are directly related.

Gas Law Calculations

• Temperature for gas law calculations needs to be in Kelvins.
• Example Boyle's Law problem: If the volume of a cylinder reduces from 10L to 5L, the pressure will change from 50 kPa to 100 kPa.
• Example Charles' Law problem: If a gas has a volume of 15L at 200K and decreases to 7L, the new temperature is approximately 93.3K

Explore matter's fundamental properties, differentiating between substances and mixtures. Understand heterogeneous and homogeneous mixtures with examples. Learn about physical properties like density and chemical properties like flammability and reactivity.