Download C07 Introduction to Chemical Reactions

C07 Introduction to Chemical Reactions
February 14, 2013
Chemical Reactions
Chemical reactions refers to the formation of new compounds. This will happen for two reasons
1. Random collision of particles.
2. The opportunity for a compound to become more stable
The Kinetic Molecular Theory (grade 9)
Kinetic means ____________________and the kinetic molecular theory (particle theory) states that all particles above ____________________________ are moving. Therefore, it is possible during this movement for two particles, molecules to come close enough, and collide with enough energy to create a new compound.
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A chemical reaction is the process that changes one or more chemical substances into
another ­ new and different substance.
Evidence of a chemical reaction ( 5 clues)
­ a new substance may be formed (precipitate)
­ release or absorption of energy (heat or light)
­ release of gas (bubbles)
­ colour change
­ odour change
Chemical reactions can be represented in many ways.
1. A Word Equation
A word equations uses the chemicals ___________________, written in a equation.
ex. 1
Gaseous hydrogen and gaseous oxygen react explosively to form water vapor.
word equation hydrogen (g) + oxygen (g) → water (g) + heat
ex 2.
Sodium metal reacts in water to produce sodium hydroxide in an aqueous solution and hydrogen gas and heat energy.
word equation 2. Skeletal Equations
A skeletal equation is one that takes the chemical names of a compound and converts them to their chemical formula. The advantage to the skeletal equation is that it gives you a sense of the number of atoms involved in a reaction. Examples
word equation hydrogen (g) + oxygen (g) → water (g) + heat
skeletal equation H2 (g) + O2 → H2 0 (l) + heat
Sodium (s) + water (l) → sodium hydroxide(aq) + hydrogen(g) + heat energy.
skeletal equation
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C07 Introduction to Chemical Reactions
February 14, 2013
Homework
A Word Equations ­ create word equations for the following examples
l.
When zinc metal and sulfur powder are heated, they form solid zinc sulfide.
2. Aluminum metal plus hydrogen chloride gas yields solid aluminum chloride plus hydrogen gas.
3. Zinc metal plus oxygen gas produces solid zinc oxide.
4. Magnesium metal plus gaseous carbon dioxide yields solid magnesium oxide plus solid carbon.
5. Sodium metal plus chlorine gas combine to form solid sodium chloride.
6. Water vapour is formed from the explosive reaction between hydrogen gas and oxygen gas.
7. Silverware reacts with the sulfur in the air to become tarnished, producing silver sulfide.
8. Iron reacts with the oxygen in the air to form rust (which is iron oxide).
9. When sodium metal is placed in a beaker of water, hydrogen gas and a sodium hydroxide solution are formed.
10. When zinc metal is placed in a solution of hydrochloric acid, hydrogen gas and a zinc chloride solution are formed. The container gets warm.
B Skeletal Equations ­ convert the following word equations into skeletal equations (formulas)
magnesium + oxygen gas → Magnesium oxide
magnesium + dihydrogen monoxide → magnesium hydroxide
sodium chloride → sodium + chlorine dihydrogen monoxide → hydrogen + oxygen
carbon tetrahydride + oxygen → carbon dioxide + dihydrogen monoxide
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