Matter - Properties and Changes Chapter 3

What is matter Chemistry is the study of matter  Matter is anything that takes up space and has mass  Mass is the measurement of how much matter is in something

Mass vs Weight Mass is the same regardless of gravity  Mass is measured using a balance Weight measures how gravity affects an object  Weight is measured using a scale

Mass vs Weight Say you travel to the Moon, where gravity is 1/6 th that of Earth? Which would be affected:  Your Mass,  Your Weight,  Neither,  Both?

Matter Matter is subdivided into categories: Matter Mixtures Pure Substances HomogeneousHeterogeneousCompoundElement

Types of Matter Matter = has mass and takes up space Pure substance = uniform, unchanging composition  Example: Distilled water always has the formula H 2 O Mixture = combo of 2 or more pure substances in which each ingredient retains its individual chemical properties  Example: Sea Water contains water, salt, magnesium, iron, phosphates, all mixed together.

Types of Mixtures Heterogeneous mix = individual substances remain distinct  Examples: dirty water tacos oil & vinegar chocolate chip cookies

Types of Mixtures Homogeneous mix = has the same composition throughout Also called a Solution Examples of solutions:  Air,  salt water,  milk,  steel

Types of Mixtures Homogeneous mix = has the same composition throughout Alloys = homogeneous mix of metals Examples:  steel  brass  jewelry

Types of Pure Substances Pure Substances are either elements or compounds Element = cannot be further separated or broken down by physical or chemical means Examples:  Na,  S,  Fe,  C

Types of Pure Substances Pure Substances are either elements or compounds Compound = 2 or more elements chemically combined Examples:  Water = H 2 O,  Salt = NaCl,  sugar = C 12 H 22 O 11

Types of Pure Substances Compounds can be broken down only by chemical means  not by physical means Compounds have different properties than the elements they are made of.  Example: H 2 O 2 H 2 O

Properties of Matter Physical property has characteristics that can be observed or measured without changing the sample’s composition. Examples: density, color, odor, taste, hardness, melting point, and boiling point

Properties of Matter Intensive property – independent of the amount of the substance sample Examples: density, melting point, boiling point

Properties of Matter Extensive property – dependent of the amount of the substance sample Examples: mass, length, width, volume

Properties of Matter Chemical property – the ability of a substance to combine with or change into one or more other substances Examples: Iron reacts with oxygen to form rust, iron does not react with nitrogen

Separation of Mixtures Mixtures are physically (not chemically) combined so separation uses physical processes based on physical properties. Separation Techniques:  The physical properties of a substance allow you to devise a method of separating the parts of a mixture.

Separation of Mixtures Separation Techniques:  Filtration  Distillation  Chromatography

Separation of Mixtures Separation Techniques:  Manual separation  Settle and Decant  Magnetic  Evaporation or crystallization

Changes in Matter Physical change  Only physical properties are altered  No new substance formed  Structure of molecules not changed Examples: water to ice, Al foil crumpled, wood cut

Changes in Matter Chemical change  New substance formed w/ new properties  Different molecules  Clues – formation of a precipitate, new gas, etc.  a.k.a chemical reaction (chem rxn)  Examples: Na + Cl  NaCl, H2 burned as rocket fuel, iron nail rust

Changes in Matter Law of Conservation of Mass  Mass is neither created nor destroyed  Mass reactants = Mass products Problem A 10.0 g sample of Mg reacts with O 2 to form 16.6g of magnesium oxide (MgO). How many grams of O 2 reacted?

Changes in Matter Given:  Mg = 10.0g Reactant  MgO = 16.6 g Product  Mg + O 2  MgO Find:  O 2 = ? g Reactant Solve:  x = 16.6  X = 6.6 g O 2