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Chemicals and Reactions

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Basic Chemistry Mixtures A mixture is two or more substances blended together (not bonded). Each substance in a mixture keeps all of its chemical and physical properties. – PowerPoint PPT presentation

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Title: Chemicals and Reactions


1
Chemicals and Reactions
  • Basic Chemistry

2
Mixtures
  • A mixture is two or more substances blended
    together (not bonded).
  • 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 dissolved Examples
    sugar, salt
  • Solvent substance doing the dissolving Example
    water

6
Mixtures
  • A solution becomes saturated when the solvent
    holds all the solute that it can. It can no
    longer dissolve solute.

7
Mixtures
  • Suspensions are a mixture of particles scattered
    throughout another. The particles do not
    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
  • Properties of compounds are usually different
    than 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
    compoundlike waterthat has all the properties
    of the compound.

12
Compounds vs. Elements
1. C Two or more elements combined 7. C Water (H2O)
2. E Made up of one type of atom 8. B Smallest unit of a substance
3. E Cannot be chemically broken down 9. E Smallest unit of matter
4. C Table Salt (NaCl) 10. B Units of matter
5. E Sodium (Na) 11. E Hydrogen (H)
6. C Glucose 12. C Can be broken down chemically
13
Formation of Chemical Bonds
  • A covalent bond is a bond formed when atoms share
    electrons to form a compound.
  • Strong physical bond

14
Covalent Bond
hydrogen
8
oxygen
2 covalent bonds
8
hydrogen
H2O Molecule
15
Formation of Chemical Bonds
  • An ionic bond is formed by the transfer of
    electrons from one atom to another.
  • It is a weak electrical attraction, not a
    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 lost
    one or more electrons.

18
Chemical Reactions
  • A chemical reaction is the process of breaking
    down existing chemical bonds of compound and
    forming new 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.
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