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Understanding Basic Chemistry: Bonds, Reactions, and Properties of Water

This module explores basic chemistry principles crucial for understanding life processes. It details the types of bonds that form compounds, including covalent and ionic bonds, and explains chemical formulas and reactions. Students will learn about mixtures, their properties, and differences from compounds. Additionally, the properties of water and concepts of pH, acids, and bases will be examined, highlighting their significance in biological systems. The impact of acids and bases on pH and the importance of buffers in maintaining homeostasis will also be discussed.

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Understanding Basic Chemistry: Bonds, Reactions, and Properties of Water

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  1. UNIT 2: Basic Chemistry BIG IDEA: Examining substances at the molecular level helps us understand basic processes of life

  2. Types of bonds that form Compounds • Covalent- each atom shares electrons with the other • Molecules are formed by this type of bond

  3. Types of bonds that form Compounds • Ionic Bond- One atom gives an electron to the other

  4. IONIC: • Creates opposite charge that holds atoms together • Form crystals

  5. Chemical Formulas • Al2O3 • 2Al2O3 Subscript shows how many atoms of the elementit is written after This number shows how many of the entire molecule their are

  6. Chemical Reactions • Reactants: The “stuff” you start with • Products: The “stuff” you end up with A + B  C Reactants Products

  7. Chemical Reactions • Change in the arrangement of atoms that creates a different substanceNumber of atoms before and after the reaction are equal. A + B  C synthesis reaction A  B + C decomposition A + B  C + D Displacement

  8. Chemical Reactions C6H12 O6+ 6O26CO2+ 6H2O C6H12 O6 + C6H12 O6 C12H22O11 + 6H2O H20  H+ + OH-

  9. Chemical Reactions- Bonds • Compounds • Atoms are chemically bound together • Definite proportions required • Properties of a compound are different from the properties of the elements that make up that compound • Made up of many particles of the same type held together by a bond using the valence electrons

  10. Mixtures • Mixtures have “ingredients” that do not bind chemically with each other • Each ingredient keeps its own properties • Definite proportions not required • Types: solution, suspension, colloid

  11. Mixtures • Solution: homogeneous; even throughout; solute (substance) completely dissolves in solvent (liquid) examples: air, • Suspension: Heterogeneous; looks even if shaken; but particles settle to bottom examples-water column in oceans and lakes

  12. Mixtures • Colloid: heterogeneous BUT does not settle; sort of in between the other two. Examples-milk and fog

  13. Mixtures vs. Compounds Look at your notes: What are three big differences between Mixtures and Compounds?

  14. Properties of Water Water is held together with special covalent bond called polar covalent bond - Means water has poles, or ends. - O is the negative end - H’s are the positive end

  15. Water is the Universal Solvent • Important solvent in many solutions • Anything with a charge will attract water molecules and dissolve • Ionic and polar molecules have charge • Nonpolar molecules (like fat) do not have charge and will not dissolve

  16. Properties of Water

  17. Properties of Water Cohesion: Water molecules stick together because of charges

  18. Cohesion Creates Surface tension - allows stickbugs to walk on water!

  19. Adhesion Water molecules stick to other charged substances like glass Glass stirring rod

  20. Concept of pH • pH = power of Hydrogen • A way of measuring how many Hydrogen ions, H+, there are in a solution • Determines whether a solution is an acid or a base

  21. Acids and Bases • Acids: a chemical that when dissolved in water releases a hydrogen ion (H+) HX (in water)  H+ + X-

  22. Properties of Acids • Taste sour – think of lemon • Turn litmus paper from blue to red • Corrodes Metal • Examples: Sulfuric Acid, Lemon Juice, Battery Acid

  23. Acids and Bases • Base: a chemical that when dissolved in water releases a hydroxide ion (OH-) XOH (in water)  OH- + X+

  24. Properties of Bases • Taste bitter – cough meds. • Turn litmus paper back to blue after acid turns it red • Can cause serious burns • Examples: Bleach, KOH, NaOH

  25. Acids and Bases - Examples • NaOH + H2O  Na+ + OH- + H2O • HCl + H2O  H+ + Cl- + H2O

  26. Acids and Bases will “cancel” each other out • When an Acid and a Base are mixed together they will “Neutralize” each other and create Water and a Salt • This is a Neutralization Reaction

  27. Neutralization Reaction • HCl + NaOH NaCl + H2O A Salt Water • HNO3 + KOH  KNO3 +H2O A salt Water

  28. pH Scale – a measure of the concentration of Hydrogen Ions Acid Neutral (water) Base 0 1 2 3 4 7 8 9 10 11 12 13 14 5 6 High H+ Low OH- High OH- Low H+ H+ = OH-

  29. Concept of pH • Where is the “safe” pH? • pH must stay between 6.5 - 7.5 in the human body • Another factor that must maintain homeostasis

  30. Concept of pH • Are there exceptions? • Stomach is acidic • Intestines are basic • Buffers are necessary • weak acids or bases that react with strong acids or bases to prevent sudden changes in pH

  31. What is the pH of Rain water?? Usually between 5.6- 5.8 - Water reacts with CO2 in air to form Carbonic Acid (H2CO3)

  32. What is the pH of Rain water?? Acid Rain: - Rain water reacts with pollutants such as Sulphur dioxide and Nitrogen oxides in air - Forms Sulphuric Acid, Nitric Acid, Ammonium Sulphate - Decreases pH even further

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