CHEMISTRY Chapters 2-8 CHAPTER 2: PROPERTIES OF MATTER

11/6/2015Chapter 2 Properties of Matter2 CLASSIFYING MATTER  Matter - Anything that takes up space and has mass  Based on their compositions, materials can be divided into pure substances and mixtures.

11/6/2015Chapter 2 Properties of Matter3 PURE SUBSTANCES (BOX 1)  pure substance (or simply a substance) - matter that always has exactly the same composition  Fixed, uniform composition  every sample has same properties.  Can be classified into 2 categories: elements and compounds

11/6/2015Chapter 2 Properties of Matter4 ELEMENTS (BOX 2)  Millions of known substances, but only about 100 elements.  Element - substance that CANNOT be broken down into simpler substances  Only 1 type of atom  fixed composition  No 2 elements contain same type of atom

11/6/2015Chapter 2 Properties of Matter5 ELEMENTS  At room temperature (20°C, 68°F, 300K) most are solids some are gases (i.e. oxygen & nitrogen) only 2 are liquids, bromine and mercury

11/6/2015Chapter 2 Properties of Matter6 ELEMENTS  1813, Jons Berzelius suggested use of symbols to represent elements.  Helps scientists to communicate without confusion

11/6/2015Chapter 2 Properties of Matter7 ELEMENTS  1 or 2 letters: 1 st capitalized, 2 nd not  Some based on Latin names Symbol for gold is Au because Latin name for gold is aurum  Sometimes name gives clue to properties hydrogen from Greek words hydro (water) and genes (forming)

11/6/2015Chapter 2 Properties of Matter8

11/6/2015Chapter 2 Properties of Matter9 COMPOUNDS (BOX 3)  compound - substance that is made from two or more simpler substances and CAN be broken down into those simpler substances  Simpler substances are either elements or compounds.

11/6/2015Chapter 2 Properties of Matter10 COMPOUNDS (BOX 3)  Always contains 2 or more elements joined in a fixed proportion.  Properties of a compound differ from those of the substances from which they are made.

11/6/2015Chapter 2 Properties of Matter11 COMPOUNDS (BOX 3)  Example: Water (H 2 O)

11/6/2015Chapter 2 Properties of Matter12 COMPOUNDS (BOX 3)  Example: Water (H 2 O)  Compound of 2 elements hydrogen (H) and oxygen (O) HH O

11/6/2015Chapter 2 Properties of Matter13 COMPOUNDS (BOX 3)  Example: Water (H 2 O)  H 2 & O 2 both gases at room temperature  H 2 can fuel a fire & O 2 can keep a fire burning  H 2 O does not burn or help other substances burn. Water decomposes into its component elements, hydrogen & oxygen, when direct electrical current is passed through it. Volume of hydrogen (right) is twice the volume of oxygen (left).

11/6/2015Chapter 2 Properties of Matter14 Example: silicon dioxide (SiO 2 ) Always 2 O atoms for each silicon (Si) atom O colorless gas Si gray solid Compound found in most light-colored grains of sand COMPOUNDS SiO 2 is a colorless, transparent solid

11/6/2015Chapter 2 Properties of Matter15 MIXTURES - (Box 4) Matter that doesn’t always have the same composition Tend to retain some of properties of their individual substances.

11/6/2015Chapter 2 Properties of Matter16 MIXTURES (Box 4) The properties of a mixture can vary because the composition of a mixture is not fixed.

11/6/2015Chapter 2 Properties of Matter17 MIXTURES (Box 4) No matter how well you stir, substances that make up mixture will not be evenly distributed. Can be classified by how well parts are distributed throughout mixture. Homogeneous Heterogeneous

11/6/2015Chapter 2 Properties of Matter18 homogeneous mixture - substances are so evenly distributed that it is difficult to distinguish one substance in the mixture from another Appears to contain only one type of substance Example: swimming pool water: H 2 O + substances that dissolve in water MIXTURES: HOMOGENEOUS (BOX 5)

11/6/2015Chapter 2 Properties of Matter19 Greek words hetero (“different”) and genus (“kind”) heterogeneous mixture - parts of the mixture are noticeably different from one another MIXTURES: HETEROGENEOUS (BOX 6)

11/6/2015Chapter 2 Properties of Matter20 MIXTURES: HOMOGENEOUS & HETEROGENEOUS

11/6/2015Chapter 2 Properties of Matter21 Stainless steel serving spoon is a homogeneous mixture of iron, chromium, and nickel. It is difficult to distinguish one substance from another. MIXTURES: HOMOGENEOUS

11/6/2015Chapter 2 Properties of Matter22 Sand is a heterogeneous mixture. It is not the same throughout. MIXTURES: HETEROGENEOUS

11/6/2015Chapter 2 Properties of Matter23 Matter mixtures pure substances compoundselementshomogeneous heterogeneous Anything that takes up space & has mass

11/6/2015Chapter 2 Properties of Matter24 Matter mixtures pure substances compoundselementshomogeneous heterogeneous Anything that takes up space & has mass Matter that always has exactly the same composition substances that CAN’T be broken down into simpler substances. Matter that doesn’t always have the same composition substances made from 2 or more simpler substances & CAN be broken down. even distribution difficult to distinguish one substance in the mixture from another. parts of the mixture are noticeably different from one another.

11/6/2015Chapter 2 Properties of Matter25

11/6/2015Chapter 2 Properties of Matter26 ELEMENTS, COMPOUNDS, AND MIXTURES (a) an element (hydrogen) (b) a compound (water) (c) a mixture (H & O) (d) a mixture (H & O) Dorin, Demmin, Gabel, Chemistry The Study of Matter, 3 rd Edition, 1990, page 68 hydrogen atoms hydrogen atoms oxygen atoms

11/6/2015Chapter 2 Properties of Matter27 Chart Examining Some Components of Air Nitrogen consists of molecules consisting of two atoms of nitrogen: Oxygen consists of molecules consisting of two atoms of oxygen: Water consists of molecules consisting of two hydrogen atoms and one oxygen atom: Argon consists of individual argon atoms: Carbon dioxide consists of molecules consisting of two oxygen atoms and one carbon atom: Neon consists of individual neon atoms: Helium consists of individual helium atoms: N2N2 O2O2 H2OH2O Ar CO 2 Ne He Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 35

11/6/2015Chapter 2 Properties of Matter28 The size of the particles in a mixture has an effect on the properties of that mixture. Key Concept: Based on the size of its largest particles, a mixture can be classified as a solution, a suspension, or a colloid. SOLUTIONS, SUSPENSIONS, AND COLLOIDS

11/6/2015Chapter 2 Properties of Matter29 Solution - mixture that forms when substances dissolve and form a homogeneous mixture Example: Sugar dissolved in water Spoonful of sugar in a glass of hot water & stir, the sugar dissolves in the water  homogeneous mixture of sugar & water. SOLUTIONS

11/6/2015Chapter 2 Properties of Matter30 Properties of liquid solutions: Particles small so… do not separate into distinct layers over time. none of the substances in the solution are trapped in the filter. can see through because light passes through them without being scattered in all directions. Particles in a solution are too small to settle out of the solution, be trapped by a filter, or scatter light. SOLUTIONS

11/6/2015Chapter 2 Properties of Matter31 Suspension - heterogeneous mixture that separates into layers over time Examples: sand mixed with water SUSPENSIONS

11/6/2015Chapter 2 Properties of Matter32 Properties of a suspension: Because suspended particles are large… suspended particles settle out of mixture (form layers) can use a filter to separate out suspended particles can scatter more light in all directions (cloudy) SUSPENSIONS

11/6/2015Chapter 2 Properties of Matter33 Colloid - contains some particles that are intermediate in size between the small particles in a solution and the larger particles in a suspension i.e.: homogenized milk, fog (water droplets in air) COLLOIDS

11/6/2015Chapter 2 Properties of Matter34 Properties of a colloid: does not separate into layers can’t use a filter to separate the parts scatters light (cloudy, opaque) COLLOIDS

Key Concepts for Solutions, Suspensions & Colloids Properties of liquid solutions: Particles small so… Particles will not separate into layers over time. None of the substances in the solution can be trapped in a filter. Can see through the solution because light passes through them without being scattered in all directions. 11/6/2015Chapter 2 Properties of Matter35

Key Concepts for Solutions, Suspensions & Colloids Properties of a suspension: Because suspended particles are large… Suspended particles settle out of a mixture (Parts WILL separate). CAN use a filter to separate out suspended particles. Can scatter more light in all directions (cloudy) 11/6/2015Chapter 2 Properties of Matter36

Key Concepts for Solutions, Suspensions & Colloids Properties of a colloid: Does NOT separate into layers. Can not use a filter to separate the parts. Scatters light (cloudy, opaque). The light will be reflected by the larger particles in a colloid. 11/6/2015Chapter 2 Properties of Matter37