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Elements, Compounds, & Mixtures

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:

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Elements, Compounds, & Mixtures

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  1. 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

  2. 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)

  3. Compounds A compound is a group of elements chemically combined in fixed ratios. • Compounds form during chemical reactions. (2H2 + O2g2H2O) • Compounds can be separated into their elements by chemical means. (2H2O g2H2 + O2) • The symbols used to describe compounds describe the exact amount of atoms on the compound. (C6H12O6) • Cannot be separated by physical means. • Considered a pure substance

  4. 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

  5. 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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