Chemicals and Reactions

Basic Chemistry

MixturesA mixture is two or more substances blended together (not bonded).

Each substance in a mixture keeps all of its chemical and physical properties.

MixturesMixtures, unlike compounds, can be separated into their individual substances by physical means.

Example: salt and water can be separated by evaporation.

MixturesA solution is a mixture of two or more substances, one dissolved in another.

Two parts of a solution are the solute and the solvent.

MixturesSolute – substance being dissolvedExamples: sugar, salt

Solvent – substance doing the dissolvingExample: water

MixturesA solution becomes saturated when the solvent holds all the solute that it can. It can no longer dissolve solute.

MixturesSuspensions are a mixture of particles scattered throughout another. The particles do not dissolve. Examples: clouds, dust, fog, smoke, mud, blood

CompoundsCompounds are two or more elements chemically joined by bonds.

They are represented by chemical formulas.

CompoundsProperties of compounds are usually different than the atoms. Example: Hydrogen(gas) + Oxygen(gas) = Water (liquid)Example: Iron + Oxygen = Rust

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

CompoundsA molecule is the smallest part of a compound—like water—that has all the properties of the compound.

Compounds vs. Elements1. C Two or more elements

combined7. 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

Formation of Chemical BondsA covalent bond is a bond formed when atoms share electrons to form a compound.

Strong physical bond

Covalent Bond

hydrogen

hydrogen

oxygen88 2 covalent bonds

H2O Molecule

Formation of Chemical BondsAn 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)

Ionic Bond

Ionic BondInstead 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.

Chemical ReactionsA chemical reaction is the process of breaking down existing chemical bonds of compound and forming new bonds.

Chemical ReactionsElements 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.

Chemical ReactionsA 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.

Chemical ReactionsLiving things need a constant supply of energy from food because all cells use more energy than they produce.

Chemical ReactionsExample reactions:Photosynthesis

Water + Carbon Dioxide Glucose (Sugar) + Oxygen

H2O + CO2 C6H12O6 + 6O2

Chemical ReactionsExample reactions: Respiration (Breathing)

Oxygen + food(glucose) water + carbon dioxide

6O2 + C6H12O6 H2O + CO2

Chemical ReactionsExample reactions: Rusting, Burning, Digestion, etc…

Reactants are on the left.Products are on the right.