CHEMISTRY#2

• Matter: anything that has mass or takes up space.
• Pure Substances: Matter that always has the same composition

  ex. table salt, sugar, sulfur,
• fixed, uniform composition: every sample of a given substance has the same properties

  2 categories

  -elements

  ex. H, O, Si, C

  -compounds   

  ex. NaCl, KBr
• Elements: - a substance that can not be broken down into simpler substances

  -119 elements

  -88 are found naturally,about 90%

  -not equally common

  -others are made in laboratories
• Elements Cont:

  -majority of the elements are not found in abundance

  -some are exceedingly rare

  -only a dozen or so make up everyday things

  primarily: carbon, hydrogen, oxygen, nitrogen 
• Compounds:  

  • a substance made of atoms of more than one element bound together
  • unique and different from the elements it contains
  • ex. Water: (H2O) liquid, clear, non toxic
• Classifying Matter Cont.

  • Mixtures- combination of more than one pure substance

  ex. salsa, air, salad, pepper.
• • Two types of mixtures

  heterogeneous and homogenous
• Heterogeneous

  -not uniform in composition

  -different components can be seen as individual substances

  ex: Oj: juice & water, pulp
• Suspension(Heterogeneous)

  -mixtures that separates into layers over time

  -suspended particles settle out of solution or are trapped by filter

  -larger particles can scatter light: will be cloudy

  ex. O.J., sand/water, muddy water
• Homogenous

  -substances are so evenly distributed that it is difficult to distinguish one substance from another

  -appears to contain only one substance

  ex. stainless steel: iron, nickel, chromium
• Solutions(Homogenous)

  -mixtures that forms when substances dissolve and form a homogenous solution

  -particles are too small to settle, scatter light, or be trapped

  ex. salt water, windshield wiper fluid
• Colloids(Heterogeneous)

  -mixtures that contain some particles that are intermediate in size between the small particles in a solution and the larger particles in a suspension.
• Colloids (Heterogeneous) do not separate into layers

  ex. homogenized milk vs. cow’s milk, fog