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Matter. The Nature of Matter. Chemists are interested in the nature of matter and how this is related to its atoms and molecules. Gold. Mercury. Chemistry & Matter. We can explore the MACROSCOPIC world — what we can see — to understand the PARTICULATE worlds we cannot see.
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The Nature of Matter Chemists are interested in the nature of matter and how this is related to its atoms and molecules. Gold Mercury
Chemistry & Matter • We can explore the MACROSCOPIC world — what we can see — • to understand the PARTICULATE worlds we cannot see. • We write SYMBOLS to describe these worlds.
A Chemist’s View of Water Macroscopic H2O (gas, liquid, solid) Symbolic Particulate
A Chemist’s View Macroscopic 2 H2(g) + O2 (g) --> 2 H2O(g) Symbolic Particulate
Physical Properties What are some physical properties? • color • melting and boiling point • odor
Properties of Matter • Intensive properties are not related to the amount of the substance • Density • Melting Point • Color • Extensive properties depend directly on the amount of substance • Mass • Volume • Length
Physical Changes • can be observed without changing the identity of the substance Some physical changes would be • boiling of a liquid • melting of a solid • dissolving a solid in a liquid to give a homogeneous mixture — a SOLUTION.
Chemical Properties and Chemical Change • Chemical change or chemical reaction — transformation of one or more atoms or molecules into one or more different molecules. • Burning hydrogen (H2) in oxygen (O2) gives H2O.
Sure Signs of a Chemical Change • Heat • Light • Gas Produced (not from boiling!) • Precipitate – a solid formed by mixing two liquids together
Physical vs. Chemical • Examples: • melting point • flammable • density • magnetic • tarnishes in air • physical • chemical • physical • physical • chemical
Physical vs. Chemical • Examples: • rusting iron • dissolving in water • burning a log • melting ice • grinding spices
MIXTURE PURE SUBSTANCE yes no yes no Is the composition uniform? Can it be chemically decomposed? Colloids Suspensions Matter Flowchart MATTER Can it be physically separated? yes no Element Homogeneous Mixture (solution) Heterogeneous Mixture Compound
Classifying matter – Key Terms • Atoms – the smallest distinctive units in a sample of matter.
Classifying matter – Key Terms • Molecules – larger units in which two or more atoms are joined together.
Classifying Matter • Pure substance – definite or fixed composition that does not vary from one sample to another. • All puresubstances are either elements or compounds.
Classifying Matter • Mixture– does not have a fixed composition.
Classifying Matter • Element– cannot be broken down into other simpler substances by chemical reactions.
Classifying Matter • Compound– made up of atoms of two or more elements, with the different kinds of atoms combined in fixed proportions.
Classifying Matter • Homogeneous mixture– same composition throughout. • Uniformly mixed at the atom/molecule level
Homogeneous Mixtures Solutions Alloys
Classifying Matter • Heterogeneous mixture – varies in composition and/or properties from one part of the mixture to another.
Heterogeneous Mixtures Rocky Road
Separation of Mixtures • Separate mixtures based on physical properties of the mixture’s components
Different Physical Property Technique Boiling Point Distillation State of Matter (solid/liquid/gas) Filtration Adherence to a Surface Chromatography Volatility Evaporation Separation of Mixtures
