Matter

• Matter is anything that has mass and occupies space.
  • All matter is made up of small particles called atoms.
  • Matter can exist as a solid, a liquid, a gas, or plasma.

• Matter can be classified as elements, compounds, and mixtures.
  
  • The atoms of any element are alike but are different from atoms of other elements.
  • Compounds consist of two or more elements that are chemically combined in a fixed ratio.
  • Mixtures also consist of two or more substances, but the substances are not chemically combined.


• Compounds can be classified in several ways, including: - acids, bases, salts - inorganic and organic compounds.

Acids

• Acids make up an important group of compounds that contain hydrogen ions.
  • When acids dissolve in water, hydrogen ions (H+) are released into the resulting solution.
  • A base is a substance that releases hydroxide ions (OH–) into solution.
  • pH is a measure of the hydrogen ion concentration in a solution.
  • The pH scale ranges from 0–14.
    • Solutions with a pH lower than 7 are acidic;
    • solutions with a pH greater than 7 are basic.
    • A pH of 7 is neutral.
  • When an acid reacts with a base, a salt is formed, along with water.

• Some physical properties, such as density, boiling point, and solubility, are characteristic of a specific substance and do not depend on the size of the sample.
• Characteristic properties can be used to identify unknown substances.
• Equal volumes of different substances usually have different masses.

Chemical Properties

• Matter can also be described by its chemical properties, which include
  • acidity
  • basicity
  • combustibility (how easily it catches fire)
  • reactivity
    
    
• A chemical property indicates whether a substance can undergo a chemical change.