Chemical reactions

Remember indications of a chemical change energy change Color change Precipitate formed Gas given off

What is energy?

Anything that is not matter and can cause a change in matter

Examples: Heat Sound light

Symbols to know

yields or reacts to form+ plus or and(s) solid(l) liquid(g) gas(aq) dissolved in watercatalyst is written on

yields signHeat is a triangle on yields sign

Remember

Ionic compounds are usually solids (s)(but they can be dissolved in water)

All acids are dissolved in water (aq) Metals are solid except Hg Br2 is a liquid

Magnesium metal and sodium chloride dissolved in water react to form magnesium chloride dissolved in water and sodium metal

Try these!

Solid magnesium reacts with oxygen in the air to form solid magnesium oxide.

Bubbles of hydrogen gas and aqueous zinc sulfate are produced when zinc metal is added to sulfuric acid

Diatomic molecules

H2 N2 O2 F2

Cl2 Br2

I2

matter cannot be created nor destroyed (its conserved).

number of atoms reacted equals number of atoms produced

take an atom inventory

Law of Conservation of

Matter

Rules for Balancing Equations

1.Write reactants on left, products on right

2 Write correct formulas3. Take an atom inventory4. Balance the number of atoms by

placing a coefficient in front of the formula(DON’T CHANGE SUBSCRIPTS)

5. Repeat until all atoms are balanced6. Put coefficients in lowest terms

Practice

Balance and write the words:

Br2(l) + NaI(aq) NaBr(aq) + I2(s)

Al(s) +CuSO4 (aq)Al2(SO4)3(aq) +Cu(s)

Practice

Mercury metal is produced by heating a mixture of mercury(II)sulfide and calcium oxide. Other products are calcium sulfide and calcium sulfate.

Types of Chemical reactions

Combination(synthesis)A + B AB

DecompositionAB A + B

Single replacementA + BX AX + B

Double Replacement AX + BYAY + BX Combustion

HxCy + O2 CO2 + H2O

Combination(synthesis)

Mg + O2 MgO

Sodium and chlorine react to form

Iron and oxygen react to form iron (III) product

Decomposition

H2O2 H2O + O2

Water decomposes with electricity Into its elements

Calcium carbonate decomposes to form calcium oxide and carbon dioxide

Hydrogen H+Tin Sn+2,Sn+4

Single replacement

Mg + HCl MgCl2 + H2

look up on activity series(p106)Mg must be higher than H for a

reaction

Mg + KCl No reactionMg is lower than K so “ no go”

Activity Series and History

What were some of the first metals used by man? Copper age @5 –4000 BC Why?

What age came next? Bronze age 3 – 2000 BC (Trojan war) What is bronze?

What age came next? Iron Age 1000 BC on

Why Bother Discussing This? Locate copper, tin and iron Copper is found in metallic form

It is an uncombined element Look below copper, gold, mercury and

silver “coinage” metals

Tin is easy to turn into its elemental form

Iron requires lots of energy!

LiKBaSrCaNaMgAlMnZnFeCdCoNiSnPbHCuAgHgAu

Ionic Compounds

When an ionic compound dissolves in water, what actually happens?

The battle between water and “columbic” attraction

•Particles of opposite charge are attracted to each other. •This attraction is called columbic attraction

Ionic Solution

So an ionic solution is really a bunch of charged particles floating around

Water “hydrates” or surrounds each particle

Water keeps the Plus and minus charges from attracting each other

If the plus and minus are more attracted to each other than to the water, then they combine and make a precipitate - it is not soluble

Double Replacement

Metal ions replace each other

All reactants are aqueous Check products on solubility

table to see if solid or aqueous

MgSO4 + NaCl BaSO4 + Ag2CO3

Combustion

Completehydrocarbon + O2 CO2 + H2O

C5H10 + O2 CO2 + H2O

IncompleteHydrocarbon + O2 CO + H2O

C + H2O

Practice

Balance and write the words:

Br2(l) + NaI(aq) NaBr(aq) + I2(s)

Al(s) +CuSO4 (aq)Al2(SO4)3(aq) +Cu(s)

Practice

Balance and write the words:

Br2(l) + NaI(aq) NaBr(aq) + I2(s)

Al(s) +CuSO4 (aq)Al2(SO4)3(aq) +Cu(s)

Practice

Balance and write the words:

Br2(l) + NaI(aq) NaBr(aq) + I2(s)

Al(s) +CuSO4 (aq)Al2(SO4)3(aq) +Cu(s)

C + O2 CO2

C-1 O-2 C- 1

O – 2