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Pure Substances & Mixtures

Pure Substances & Mixtures. Unit 2. Pure Substance. A pure substance is a sample of matter, either a single element or a single compound, that has definite chemical and physical properties. It cannot be purified any further without destroying the substance.

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Pure Substances & Mixtures

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  1. Pure Substances & Mixtures Unit 2

  2. Pure Substance • A pure substance is a sample of matter, either a single element or a single compound, that has definite chemical and physical properties. • It cannot be purified any further without destroying the substance. • Pure substances are made up of only one kind of matter.

  3. Elementally Pure • An Element is a substance that cannot be separated or broken down into simpler substances by chemical means • There are 92 naturally occurring elements • Elements are Organized by atomic number on the Periodic Table • Elements higher than #92 are man-made

  4. Up and Atom • An Atom is the smallest unit of an element that maintains the properties of that element. • They are very small with diameters ranging from • 0.64x10-10 m (Hydrogen) to • 4.70x10-10 m (Cesium)

  5. IBM Goes Nano • In 1990, two researchers at IBM in San José, CA, arranged 35 Xenon atoms to make their logo. • 350 million of these logos will fit in a period.

  6. Compounding Interest • A compound is a substance made up of atoms of two or more different elements joined by chemical bonds • H2O - water • C6H12O6 - glucose • H2SO4 – sulfuric acid

  7. Mol-uh-kyool • A Molecule is the smallest unit of a substance that keeps all the physical and chemical properties of that substance. • They consist of two or more atoms bonded together. • Can be all same element or many different • All Same: H2, O2, O3, S8 • Different: H2O, HNO3, C8H10N4O2

  8. Practice Yer Subscripts • Write the chemical formula for a compound that contains the following atoms: • 1 Sulfur and 3 oxygen atoms • 2 Phosphorous atoms and 5 oxygen atoms • 6 carbon atoms and 12 hydrogen atoms SO3 P2O5 C6H12

  9. Gimme a Re-Mix • A mixture is a combination of two or more substances that are not chemically combined. (They do not react.) • They can be separated without destroying the individual substances. • There are two main types of mixtures • Heterogeneous • Homogeneous

  10. Just to Be Different • A Heterogeneous mixture is when the particles are not uniformly intermingled • The prefix “Hetero-” means “different” • They have visibly different parts • These mixtures can be separated by mechanical methods • Picking out pieces • Centrifuge • Filtration

  11. Following the Herd • A Homogeneous mixture made up of uniformly intermingled particles • The prefix “Homo-” means “Same” • They do not contain visibly different parts • These mixtures cannot be separated mechanically, but by their physical & chemical properties: • Precipitation - Evaporation / Distillation • Crystallization - Chromatography

  12. Double Agent-like • Colloids are heterogeneous mixtures that may appear to be homogeneous. • There are tiny bits of a dispersed phase suspended in the continuous phase (main medium). • Because the dispersed phase is so small, it often looks like a cloudy homogeneous mixture. • e.g. Milk, jello, cough medicine

  13. Distillation (Fractional Distillation) • Separation of homogeneous mixture by differences in Bp. • Substances w/ lower Bp “boil off” and are collected in pure factions • Azeotropic mixtures cannot be distilled.

  14. Which Technique is used to separate: • Sand from water • Colors from a dye mixture • Methanol (Bp 700C) from water (Bp 1000C) • Blood platelets from plasma Filtration Chromatography Distillation Centrifugation

  15. A Rose by Any Other Name… • We call homogeneous mixtures Solutions • They can be • Solids (known as alloys ) • Liquids (most common usage) • Gases (you’re swimming in one, now) • We will devote an entire unit to solutions

  16. Recap • Pure Substances • Elements: cannot be broken down further • Compounds: made up of more than 1 element • Mixtures • Heterogeneous: can be mechanically separated • Homogeneous (aka solutions): cannot be mechanically separated, must be separated using physical and chemical properties

  17. States of Matter & Models • All substances can be in several states depending on the arrangement of the atoms/molecules.

  18. Matter Concept Map Matter Pure Substance Mixture Physical Separation Chemical Element Compound Homogeneous Heterogeneous

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