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Note Taking Guide: Classification of Matter

Essential Questions

• What is matter?

• How can we classify matter?

• What is a pure substance verses a mixture?

Matter

• All matter is composed of atoms

• Atoms are extremely small building blocks of matter

• Atoms cannot be broken down into smaller pieces by chemical means

• Atoms are the smallest distinct units in a sample of matter

Pure Substances

• Element

• Pure substance composed of one type of atom

• cannot be decomposed into other substances.

• Represented by one or two letter symbol

• EX: copper wire (Cu), aluminum foil (Al)

• Molecule

• Combination of 2 or more same atom that are covalently bonded.

• A molecule is the smallest particle of a substance which exhibits the physical and chemical characteristics of the substance.

• Diatomic molecules of elements: H2 O2 N2 Cl2 F2 I2 Br2

• Compound

• Composed of two or more elements chemically combined in a fixed ratio

• Properties differ from those of individual elements

• Represented by a chemical formula

• EX: water (H2O) table salt (NaCl)

• Laws for Compounds

• Law of Definite Composition

• A given compound always contains the same, fixed ratio of elements.

• Law of Multiple Proportions

• Elements can combine in different ratios to form different compounds.

Mixtures

• Mixtures are two or more substances that are physically combined.

• Mixtures do not have a fixed composition

• Mixtures do not have constant boiling points or melting points

• Variable composition

• Components retain their characteristic properties

• May be separated into pure substances by physical methods

• Mixtures of different compositions may have widely different properties.

• Mixtures can be described by how uniform they are throughout.

• Heterogeneous mixture

• Two or more phases (with same or different physical states)

• Each phase has different properties

• Not uniform throughout

• Examples: oil and water, sand and water, milk, fresh squeezed lemonade

• Homogenous mixture

• One phase – must always be the same

• Uniform throughout

• Same composition in a sample

• Examples: sugar, salt water, rubbing alcohol, alloys like brass or stainless steel

Make a Matter flowchart

Matter

Check for Understanding

Classify the following as an element, compound, or mixture (heterogeneous or homogenous)

|1. Penny | |9. Salad dressing | |

|2. Air | |10. Table salt | |

|3. Aluminum foil | |11. Sea water | |

|4. Windex | |12. Water | |

|5. Steel | |13. Graphite | |

|6. Oxygen | |14. Pepper | |

|7.Sugar | |15. Paint | |

|8.Chlorine gas | | | |

Try some practice problems on your own

Classify the following as an element, compound, or mixture (heterogeneous or homogenous).

|1. hydrogen peroxide | |9. steel | |

|2. carbon dioxide | |10. calcium | |

|3. pizza | |11. lead | |

|4. rust | |12. choc chip cookie | |

|5. apple juice | |13. kool aid | |

|6. carbon | |14. muddy water | |

|7. carbon | |15. air | |

|8. carbon monoxide | |16. brass | |

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