Chemicals and Reactions

1. Chemicals and Reactions Basic Chemistry

2. Mixtures • A mixture is two or more substances blended together (notbonded). • Each substance in a mixture keeps all of its chemical and physical properties.

3. Mixtures • Mixtures, unlike compounds, can be separated into their individual substances by physical means. • Example: salt and water can be separated by evaporation.

4. Mixtures • A solution is a mixture of two or more substances, one dissolved in another. • Two parts of a solution are the solute and the solvent.

5. Mixtures • Solute – substance being dissolvedExamples: sugar, salt • Solvent – substance doing the dissolvingExample: water

6. Mixtures • A solution becomes saturated when the solvent holds all the solute that it can. It can nolongerdissolve solute.

7. Mixtures • Suspensions are a mixture of particles scattered throughout another. The particles donot dissolve. Examples: clouds, dust, fog, smoke, mud, blood

8. Compounds • Compounds are two or more elements chemically joined by bonds. • They are represented by chemical formulas.

9. Compounds • Propertiesof compounds are usually differentthan the atoms. Example: Hydrogen(gas) + Oxygen(gas) = Water (liquid)Example: Iron + Oxygen = Rust

10. Compounds • Compounds can be separated into their elements only if the chemical bonds are broken. This can be done by chemical means (chemical reaction)

11. Compounds • A molecule is the smallest part of a compound—like water—that has all the properties of the compound.

12. Compounds vs. Elements

13. Formation of Chemical Bonds • A covalent bond is a bond formed when atoms shareelectrons to form a compound. • Strongphysical bond

14. Covalent Bond hydrogen 8 oxygen 2 covalent bonds 8 hydrogen H2O Molecule

15. Formation of Chemical Bonds • An ionicbond is formed by the transferof electronsfrom one atom to another. • It is a weakelectrical attraction, nota physical bond.Example: table salt (NaCl)

16. Ionic Bond

17. Ionic Bond • Instead of being neutral, atoms of sodium and chlorine making up salt become charged. • Ions are charged atoms that have gained or lostone or moreelectrons.

18. Chemical Reactions • A chemicalreaction is the process of breaking down existing chemical bonds of compound and formingnew bonds.

19. Chemical Reactions • Elements combine in ways that cause their atoms to be stable. • The energy required to start a chemical reaction is activation energy and the most common form of this energy is heat.

20. Chemical Reactions • A reaction that gives off more energy than it uses up is an exothermic reaction. • A reaction that gives off less energy than it uses up is an endothermic reaction.

21. Chemical Reactions • Living things need a constant supply of energy from food because all cells use more energy than they produce.

22. Chemical Reactions • Example reactions:Photosynthesis Water + Carbon Dioxide Glucose (Sugar) + Oxygen H2O + CO2C6H12O6 + 6O2

23. Chemical Reactions • Example reactions: Respiration (Breathing) Oxygen + food(glucose)  water + carbon dioxide 6O2 + C6H12O6 H2O + CO2

24. Chemical Reactions • Example reactions: Rusting, Burning, Digestion, etc… • Reactants are on the left. • Products are on the right.