Matter Chapter 2

The Basics of Matter Matter – is anything that has mass and takes up space – it is the “stuff” of which the universe is composed Extensive properties – depend on the amount of matter in a sample Mass, Volume Energy, molarity (dilute or concentrated) Intensive properties – depends on the type of matter in a sample, not the amount of matter Density, freezing pt., boiling pt., absorbency, elasticity

The States of Matter State Definition Examples Solid Rigid; has a fixed shape and volume Ice cube, diamond, iron bar Liquid Has a definite volume but takes the shape of its container Gasoline, water, alcohol, blood Gas Has no fixed volume or shape; takes the shape and volume of its container Air, helium, oxygen

Physical Properties Things you can tell about a substance just by looking at it You don’t need to alter the composition of the substance to determine these Examples: Color - density Odor - melting point Volume - boiling point

mixtures and pure substances

PURE SUBSTANCES Always have the same composition Pure substances are either elements or compounds Examples: Pure water (not lake/ocean water) Copper Zinc rubbing alcohol

MIXTURES A substance with variable composition Made up of multiple pure substances Examples: Air Wood Coffee Cookie dough

Two Types of Mixtures Homogeneous mixture – looks the same throughout – can’t see different parts Ex: Kool-Aid, sugar cookie dough Heterogeneous mixture – can see the different parts Ex: chocolate chip cookie dough, sand and water solution

Practice State whether each of the following is a pure substance, a homogeneous mixture, or a heterogeneous mixture. Maple syrup The oxygen and helium in a scuba tank Oil and vinegar salad dressing Common salt (sodium chloride – NaCl)

Practice State whether each of the following is a pure substance, a homogeneous mixture, or a heterogeneous mixture. Maple syrup HOMOGENEOUS MIXTURE The oxygen and helium in a scuba tank HOMOGENEOUS MIXTURE Oil and vinegar salad dressing HETEROGENEOUS MIXTURE Common salt (sodium chloride – NaCl) PURE SUBSTANCE

Separation of mixtures

Distillation Boil the liquid off of a solution and leaves the other components behind Laboratory display of distillation: 1: A heating device 2: Still pot 3: Still head 4: Thermometer/Boiling point temperature 5: Condenser 6: Cooling water in 7: Cooling water out 8: Distillate/receiving flask 9: Vacuum/gas inlet 10: Still receiver 11: Heat control 12: Stirrer speed control 13: Stirrer/heat plate 14: Heating (Oil/sand) bath 15: Stirring means e.g.(shown), anti-bumping granules or mechanical stirrer 16: Cooling bath.

Filtration Separates a liquid from the solid The liquid passes through the filter paper, but the solid particles are trapped

Summary – Breaking Down Matter HOMOGENEOUS MIXTURES HETEROGENEOUS MIXTURES Physical methods PURE SUBSTANCES ELEMENTS COMPOUNDS Chemical methods

Elements and Compounds

ELEMENTS Fundamental substances that cannot be broken down into other substances by chemical means Found on the Periodic Table of Elements (if it’s not on the chart, it’s not an element) Examples: Aluminum Oxygen Hydrogen

COMPOUNDS Compounds are combinations of different elements. They can be broken down into their constituent elements by chemical changes. A compound always has the same composition (i.e., the same combination of elements). Examples: Water (H2O) Carbon Dioxide (CO2)

Element or Compound? Hydrogen peroxide (H2O2) Mercury (Hg) Vanadium (V) Sodium chloride (NaCl)

Element or Compound? Hydrogen peroxide (H2O2) Mercury (Hg) Vanadium (V) Sodium chloride (NaCl)

Chemical and Physical Properties

Physical Properties Things you can tell about a substance just by looking at it You don’t need to alter the composition of the substance to determine these Examples: Color - density Odor - melting point Volume - boiling point

Chemical Properties These refer to the ability of a substance to form new substances (i.e., its reactivity) Examples: propane burns in the air Baking soda fizzes if mixed with vinegar A marshmallow gets black when toasted too long in a campfire Hydrogen and oxygen react violently

Chemical or Physical? The boiling point of a certain alcohol is 78°C. Diamond is very hard. Sugar ferments to form alcohol. Gallium metal melts in your hand. Platinum does not react with oxygen at room temperature. Your paper is white.

Chemical or Physical? The boiling point of a certain alcohol is 78°C. Diamond is very hard. Sugar ferments to form alcohol. Gallium metal melts in your hand. Platinum does not react with oxygen at room temperature. Your paper is white. Green is physical. White is chemical.

Chemical and physical changes

Physical Changes Physical changes do not affect the composition of the substance. Examples: State changes (solid liquidgas) Melting Evaporating Freezing etc Breaking a substance into smaller pieces

Chemical Changes Chemical changes involve a change in the composition of the substance. Examples: Burning something Reacting two substances to make something new Running an electric current through water to decompose water into hydrogen and oxygen

Some practice… Chemical or Physical? Iron metal is melted. Iron combines with oxygen to form rust. A piece of wood is burned in a fireplace. A rock is broken into small pieces. A log of wood is chopped up with an axe into smaller pieces of wood. Water evaporates to become water vapor.

Some practice… Chemical or Physical? Iron metal is melted. Iron combines with oxygen to form rust. A piece of wood is burned in a fireplace. A rock is broken into small pieces. A log of wood is chopped up with an axe into smaller pieces of wood. Water evaporates to become water vapor. Green is physical. White is chemical.

Recognizing a Chemical Change Formation of a precipitate A solid that forms and settles out of a liquid mixture Change in color Some reactions result in a change from one color to another Production of a gas Bubbles must be a new substance Results of physical change are not new substances (ex: boiling) Transfer of energy Burning something gives off energy in the form of heat and light

Law of Conservation of Mass “During any chemical reaction, the mass of the products is always equal to the mass of the reactants.” REACTANTS  PRODUCTS