Matter – Classifications, Properties and Changes 1

Universe Classified Matter, the stuff of which the universe is composed is the part of the universe that has mass and volume (occupies space) Matter can be classified by noticing the similarities and differences in the characteristics of the substances under observation and then grouping them in various manners. 2

Figure 3.1: Liquid water takes the shape of its container.

Figure 3.2: The three states of water.

States of Matter solid, liquid, gas 6

Properties of Matter Properties can be either  directly observable or  inferred from the manner in which one piece of matter interacts with an other piece of matter in the universe Physical Properties are the characteristics of matter that can be observed without changing its composition Characteristics that are directly observable. Chemical Properties are the characteristics that determine how the composition of matter changes as a result of contact with other matter or the influence of energy. Characteristics that describe the behavior of matter. 7

Classify Each of the following as Physical or Chemical Properties  The boiling point of ethyl alcohol is 78°C.  Diamond is very hard.  Sugar ferments to form ethyl alcohol. 8

Changes in Matter Physical Changes are changes to matter that do not result in a change in the fundamental components that make that substance State Changes – boiling, condensing, melting, freezing, subliming, depositing Chemical Changes involve a change in the fundamental components of the substance Produce a new substance Chemical reaction (reacts, burns =combusts, tarnishes, rusts, ferments, rots, degrades) Reactants  Products 9

Gallium metal has such a low melting point (30°C) that it melts from the heat of a hand.

Oxygen combines with the chemicals in wood to produce flames. Is a physical or chemical change taking place? Source: Jim Pickerell/ Stone/Getty Images

Figure 3.3: Electrolysis, the decomposition of water by an electric current, is a chemical process. 12

Classify Each of the following as Physical or Chemical Changes  Iron is melted.  Iron combines with oxygen to form rust.  Sugar ferments to form ethyl alcohol. 13

Elements and Compounds Pure Substances which cannot be broken down into simpler substances by chemical reactions are elements Most pure substances are chemical combinations of elements. These are compounds. Compounds are made up of elements Compounds can be broken down into elements Properties of a compound are not related to the properties of the elements that compose it Same chemical composition at all times Compounds are NOT found on the periodic table! 14

Classification of Matter Homogeneous = uniform throughout, appears to be one thing pure substances (elements and compounds) solutions (usually liquid phase, always homogeneous mixtures) alloys (solid phase homogenous mixtures) Heterogeneous = non-uniform, contains regions with different properties than other regions one phase usually solid ALL PURE SUBSTANCES ARE HOMOGENEOUS Mixtures may be Homogeneous or Heterogeneous 15

Figure 3.4: When table salt is stirred into water (left), a homogeneous mixture called a solution forms.

Figure 3.5: Sand and water do not mix to form a uniform mixture. After the mixture is stirred, the sand settles back to the bottom. 17

Pure Substances vs. Mixtures Pure Substances All samples have the same physical and chemical properties Constant Composition - all samples have the same composition Homogeneous - same phase throughout Separate into components based on chemical properties Mixtures Different samples may show different properties Variable composition (e.g. 3% hydrogen peroxide solution, 30% hydrogen peroxide solution) Homogeneous or Heterogeneous Separate into components based on physical properties All mixtures are made of pure substances 18

Alloys Homogeneous Mixtures Steel (a mixture of iron and carbon) Stainless Steel (iron, nickel, chromium) Brass (copper and zinc) Bronze (copper and tin) Nichrome - (Nickel and chromium) < 24K Gold and colored Golds Sterling Silver (92.5% Ag rest usually Cu) 19

Identity Each of the following as: a Pure Substance, a Homogeneous Mixture or a Heterogeneous Mixture  Gasoline  A river with gravel on the bottom  Copper metal  Steel 20

Separation of Mixtures Mixtures are separated based on the different physical properties of the components Physical change 21 EvaporationVolatility ChromatographyAdherence to a Surface FiltrationState of Matter (solid/liquid/gas) DistillationBoiling Point TechniqueDifferent Physical Property

Figure 3.6: Distillation of a solution consisting of salt dissolved in water.

Figure 3.10: The organization of matter.