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Elements, Compounds, & Mixtures Objectives: 1. Explain the difference between an element and a compound. 2. Compare heterogeneous and homogeneous mixtures. 3. Describe several techniques to separate mixtures. Key Terms: Element, compound, pure substance, mixture, heterogeneous mixture, homogeneous mixture
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Matter Matter is defined as anything having mass that occupies space. Density is the measurement of matter (Mass/Vol) The atom is the basic unit of matter A group of similar atoms is called an element An element cannot be separated into simpler substances by physical or chemical means. Considered a pure substance There are slightly more than 100 known elements. (listed on the periodic table) The periodic table organizes elements by their properties. Can be represented by a one or two letter abbreviation. (C,H,O,N,P,Na,Cl,Al,Ca)
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Compounds A compound is a group of elements chemically combined in fixed ratios. Compounds form during chemical reactions. (2H 2 + O 2 2H 2 O) Compounds can be separated into their elements by chemical means. (2H 2 O 2H 2 + O 2 ) The symbols used to describe compounds describe the exact amount of atoms on the compound. (C 6 H 12 O 6 ) Cannot be separated by physical means. Considered a pure substance
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Mixtures Aggregates of substances (compounds, elements, or mixtures) physically combine to form mixtures Mixtures can be homogeneous (Also called a solution) Do not contain visibly different parts – milk Particles are equally distributed The solution is in a single phase Mixtures can be heterogeneous Visibly different parts Unequally mixed Separates under normal conditions May be in different phases Mixtures may be separated by physical means
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Physical Separation filtration – removal of a solid substance by size distillation (boiling) – removal of a liquid substance by condensing the vapor crystallization (evaporation) – removal of a substance that is dissolved in solution chromatography (flowing along a stationary surface) – separated by mass (lightest travels furthest) centrifugation (spinning to find differences in weight) - separated by mass (most massive on the outside)
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