Chemistry: The Study of Change

• Macroscopic

  visible to the naked eye.
• Microscopic 


  things not seen with the naked eye.
• Scientific method


  Systematic approach in research
• Scientific method

  
• Hypothesis


  A tentative explanation for a set of observations
• Hypothesis

  Tested →Modified (vice versa)
• Law


  A concise statement of a relationship between phenomena that is always the same under the same conditions
• Force = mass x acceleration
• Theory


  A unifying principle that explains a body of facts and/or those laws that are based on them
• Atomic theory


  The idea that all matter is made up of tiny particles called atoms.
• In 1940 George Gamow hypothesized that the universe began with the gigantic explosion or big bang.

  Experimental support:

  • Expanding Universe
  • Cosmic Background Radiation
  • Primordial Helium
• The three states of matter

  Solid, liquid, gas
• Chemistry 


  The study of matter and the changes it undergoes
• Matter


  Anything that occupies space and has mass
• Substance


  A form of matter that has a definite composition and distinct properties
• Mixture


  A combination of two or more substances in which the substances retain their distinct identities
• Homogeneous mixture


  Composition of the mixture is the same throughout such as milk, solder, and soft drink
• Heterogeneous mixture


  Composition is not uniform throughout such as cement, iron fillings in the sand
• Element


  A substance that cannot be separated into simpler substances by chemical means
• • 114 elements have been identified
  • 82 elements occur naturally on earth such as gold, aluminium, lead, oxygen, and carbon
  • 32 elements have been created by scientist such as technetium, americium, and seaborgium
• Compound


  A substance composed of atoms of two or more elements chemically united and fixed portions
• Compounds can only be separated into their pure components (elements) by chemical means

  Example: Water (H20)
• Classifications of Matter

  
• Physical change


  Does not alter the composition or identity of a substance. Ex: Ice Melting and sugar dissolving in water
• Chemical change


  Alters the composition or identity of the substances involved. Ex: hydrogen burns in air to form water
• Extensive property


  Extensive property of a material depends upon how much matter is being considered.
• Intensive property


  Intensive property of a material does not depend upon how much matter is being considered.
• Scientific notation:

  N x 10^n

  • Where N is between number 1 and 10
  • n is a positive or a negative integer
• Accuracy 


  How close a measurement is to the true value.
• Precision


  How close a set of measurements are to each other