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Understanding Mixtures, Substances, and Chemical Bonds in Matter

This overview covers the essential characteristics of mixtures and substances, including homogeneous and heterogeneous mixtures. It explains the distinction between elements and compounds, highlighting how compounds cannot be separated without altering their nature. The text delves into atomic structure, including protons, neutrons, and electrons, and introduces chemical bonding types: ionic, covalent, and metallic. It also discusses the significance of water as a universal solvent, the concept of hydrogen bonds, and the principles of solubility in various contexts.

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Understanding Mixtures, Substances, and Chemical Bonds in Matter

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  1. Objective #4 Structures & Properties of Matter

  2. MIXTURES • Mixtures contain more than one kind of matter.

  3. HOMOGENEOUS MIXTURE • A mixture that is the same throughout. • Examples: coffee brass air

  4. HETEROGENEOUS MIXTURE • A mixture in which different samples are not necessarily the same. • Examples: chicken soup salad dressing

  5. All mixtures share one common property: • They can be separated by ordinary physicalmethods. Examples: sorting, filtering, solubility, magnetic properties, density, heating, or cooling.

  6. SUBSTANCES • Substances cannot be separated by physical methods. • Examples: salt gold

  7. ELEMENTS • Some substances are elements and contain only one kind of matter (atoms). They cannot be separated by ordinary chemical or physical methods. • Examples: silver helium See the periodic table for a complete list of the elements!

  8. COMPOUNDS • Compounds contain two or more kinds of matter (atoms), but cannot be separated without changing the substance. • Examples: water sugar

  9. ATOMS • Atomic number = number of protons • In a neutral atom, the number of electrons = the number of protons

  10. MASS NUMBER mass number=protons+neutrons Ex. Carbon has 6 protons +6 neutrons . 12 mass number

  11. ATOMIC MASS • Atomicmass is the average of all the known isotopes of an element.

  12. Isotopes • Atoms of the same element that have differentnumbers of neutrons. • Example: C-12 has 6p & 6n C-14 has 6p & 8n

  13. ELECTRONS • Electrons are arranged into energylevels that hold a specific number, within the electroncloud. • The farther away from the nucleus, the higher the energystate.

  14. Periodic Table • Elements listed by increasing atomic number. • Groups(families) – elements arranged in COLUMNS (up & down)with similar chemical properties. • Rows (left to right) tell how many energy levels are occupied in the electron cloud.

  15. Valenceelectrons- electrons in the outermost energy level of the electron cloud.

  16. Reading the periodic table Periodictable can show different information.

  17. Chemical Bonds • Recall that atoms gain, lose, or share electrons to get a total of 8 (octet rule) & become stable. • Both metals AND nonmetals can gain or lose electrons • ONLY nonmetals can SHARE • Ionic bond = metal + nonmetal • Covalent bond = nonmetal + nonmetal • Metallic bond = metal + metal

  18. Benchmark Question

  19. Sodium has 1 valence electron. When it loses that electron it becomes stable. sodium atom sodium ion Atoms with an electrical charge are called ions.

  20. Chlorine has 7 valence electrons. • If Cl gains 1 electron, its valence shell will be full and stable. chlorine ion chlorine atom

  21. IONIC BOND • When two oppositely charged ions come together to form an ionic compound YES!!

  22. o o O o o H H o o x x Covalent Bonds (NONmetals ONLY) • Covalentbonds are formed when electrons are shared. Shared pair of electrons Shared pair of electrons H – O – H Water molecule

  23. Diatomicmolecules: • – covalently bonded atoms of the same type. • Exs: H2 Cl2 F2 I2 O2 Br2 N2 S T t

  24. Polar vs. Nonpolar • Sometimes electrons are shared UNEQUALLY in covalent bonds. • When electrons are shared EQUALLY the bond is NONpolar • When electrons are shared UNEQUALLY the bond is POLAR

  25. Electronegativity • Electronegativity – attraction an atom has for shared pair of e- • Elements in Group 17 have highest electronegativity. • Elements in Groups 1 and 2 have lowest electronegativity.

  26. WATER • Water is the “universal solvent” which means it can dissolve MOST things • Water is a POLAR molecule which means it has a positive & negative end (kind of the like the poles of a magnet) Positive end Negative end

  27. Benchmark Question

  28. HYDROGEN BONDS • When the positive & negative ends attract and forms bonds with EACH OTHER • H-bonds are the reason why ice is less dense than water

  29. DISSOLVING IN WATER • Rule: LIKES DISSOLVE LIKES • Water is polar so can dissolve any other polar substance • Nonpolar substances will ONLY dissolve in NONpolar solvents like alcohol or oil. • That is why OIL (nonpolar) and WATER (polar) do NOT mix

  30. Benchmark Question

  31. Parts of a solution: • Solvent – does the dissolving. Is present in the greatest amount. • Solute – gets dissolved. All remaining parts or components. • When particles are evenly spread out, the solute has dissolved.

  32. Dissolving Rates • Ways to increase: • Stir, increase the temperature, crush the solid into smaller pieces. • Ways to decrease: • STOP stirring, decrease the temperature, use larger pieces of solid.

  33. How much is dissolved? • Saturated – no more solute will dissolve; full. • Unsaturated – more solute can be dissolved; not full. • Supersaturated – more solute is dissolved than is normally possible; unstable.

  34. Solubility of Gases: • Depends on pressure, as well as temperature. • Solubility of a gas in a liquid increases ( ) with increasing ( ) pressure.

  35. What is a fluid? • A fluid is matter that can flow or be poured. • Includes liquids and gases.

  36. Density of Fluids • REMEMBER: Density = Mass/Volume • Because matter EXPANDS when heated, the volume INCREASES and the density DECREASES • WATER is the only exception because water actually expands when it FREEZES!!!! So ICE is LESS dense than WATER!!!

  37. Buoyancy • Buoyancy - measure of the upward pressure (force) a fluid exerts on an object.

  38. Archimedes’ Principle • The force exerted on an object is equal to the weight of the fluid displaced by the object. • An object sinks when the buoyant force is less than its weight.

  39. If the buoyant force is greater than the object’s weight, it will float.

  40. Benchmark Question

  41. Benchmark Question

  42. V8 Juice ketchup Viscosity of Fluids • A measure of a material’s resistancetoflow. • High-viscous fluids take longer to pour from containers. • Which is more viscous? or

  43. Viscosity of a liquid decreases with an increase in temperature • So, fudge is easier to pour when it’s hot.

  44. What is pH? • Scale (powers of 10) based on concentration of H+ ions in solution • ACIDIC is 0 - 6 • BASIC is 8 - 14 • NEUTRAL is 7

  45. Benchmark Question

  46. Low pH means high H+ ion concentrationProperties: Low pH – 0 to 6 Sour taste Turns litmus red Corrosive Reacts with metals Electrolytes Acids - chemicals that release H+ ions in a solution.

  47. Soap Bases are chemicals that release OH- ions in solution. Properties • High pH – 8 to 14 • Bitter taste • Feels slippery • Turns litmus blue • Corrosive • Reacts with fats

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