Chemical reactions
The Big Idea
• Matter cannot be created or destroyed, but can change form.
• In this unit we will be able to explain how these reactions
cause changes in the matter without creating any new matter
or destroying any matter.
• Reactants- the starting compounds or elements
• Products- the ending compounds
Chemical reactions up in the air
• Roller coaster book – pgs. 446-447
• Read- take notes- share with partner- be ready to discuss
• What reactions are taking place?
• What are the reactants ?
• What are the products?
• Why is that a problem?
The problems
• Density
• Distance of ozone above the earth’s surface.
• Accurate measure of ozone
• Global increase in UV irradiance during the past 30 years (1979–2008) estimated from
satellite data
• Amount of UV radiation
• To his surprise, he found that increased cloudiness in the southern hemisphere
produced a dimming effect that increased the shielding from UV compared to
previous years.
• Positives of UV radiation
• Negatives of UV radiation
Read pages 442-445 in the roller coaster book
and take notes that answer the following:
• What are chemical reactions?
• What are reactants?
• What are products?
• How do chemical reactions operate within the law of conservation of mass?
• What does a written equation communicate?
• What are the symbols used in chemical equations and what do they mean?
• What are coefficients and why must they be used?
• Answer questions 1, 2, & 3 on page 445
• What are chemical reactions?
• What are reactants?
• What are products?
• How do chemical reactions operate within the law of conservation
of mass?
• What does a written equation communicate?
• What are the symbols used in chemical equations and what do
they mean?
• What are coefficients and why must they be used?
• Answer questions 1, 2, & 3 on page 445
Notes:
Therefore: putting
this into words:
Mixing the reactants Methane
gas with Oxygen gas reacts to
produce the products of carbondioxide gas and liquid water
Analogies (due Friday)
• Example- (You may not use this one.)
• A chemical reaction is like making cookies
• The reactants are like the butter, flour, sugar, eggs and
chocolate chips.
• The products are like the cookies.
• Think- music- teams- building something
Quiz – intro to reactions
• Turn in analogies – because of testing, you may turn it in by Monday
without any late penalty.
• Complete quiz and turn it over on your desk.
• Work on analogy if you have not completed it.
Quiz – intro to reactions- key
Fe (cr) + O2 (g)  Fe2O3 (cr)
Element/Compound
Reactant or Product?
State of Matter
Fe
Reactant
Crystalline solid
O2
reactant
Gas
Fe2O3
Product
Crystalline solid
Quiz – intro to reactions
• According to the law of the conversation of mass, how does the mass of the
products in a chemical reaction compare to the mass of the reactants?
•
A. The mass of the products is greater.
•
B. The mass of the reactants is greater.
•
C. There is no relationship.
•
D. The masses are equal.
According to the law of conservation of mass, if two atoms of hydrogen are
used as a reactant, how many atoms of hydrogen must be part of the
product?
•
A. 2
B. 0
•
C. 1
D. 4
Quiz – intro to reactions
Cl + O3 --> ClO + 02
Chemical reaction (describe what is happening in the reaction)
• The reactants of chlorine (Cl) and ozone (O3) react to make the products of
chlorine monoxide (ClO) and breathable oxygen (O2)
Causes
• air conditioning systems- Volcanic eruptions, plants, ocean life, forest fires,
fungi
• Effects
• Increased Skin cancer- cataracts- death for plants, animals and man
Reasons to question Man’s contribution to “Ozone depletion”.
Use pages 200 and 202-204 to answer the
following questions to prepare for lab Monday
• What are some evidences that a chemical change has taken place?
• 202-204
• What are some things that effect the rate of chemical reactions and
how do they effect them? (answer on your lab sheet)
• Write a hypothesis for the lab on Monday
Rate of reactions lab: (110 points)
Analyzing the data (back page)
• Deal with the data from each individual experiment
• Compare the numerical data (averages, range, differences, etc..)
• Compare the rates of all the data averaged and draw your conclusion from this
• Points by section BD-20; Hy-10; Pr-10; DT1-10; DT2-10; Gr-20; DA-20; Co-10
Agenda for today
• Check types of reactions practice
• Take quiz
• Check quiz
• Pass out types of reactions analogies homework
• Balancing equations notes
• Balancing act assignment
Balancing Notes
• Balancing means the same number of atoms of each
element in the reactants and in the products.
• The equation below tells us what is in the reaction but not
how many of each thing…
•
H2O --> H2 + O2
• Why must the equations be balanced?
• Law of Cons. of Matter (matter can neither be created nor destroyed but it can change form)
Is it balanced?
•
1. NaOH + HCI →
•
2. Zn + HCl
H2O + NaCl
→
ZnCl2 + H2
• How to balance…….
•
*Add numbers in front of the entire compound only
•
NO numbers added at the end
•
NO numbers added in the middle
For example…….
•O2 + P --> P4O10
There aren’t enough oxygen or phosphorus atoms
in the reactants so we put numbers in front…
• 5O2 + 4P --> P4O10
• (that means we need 5 oxygen molecules and 4 phosphorus
atoms for this reaction to happen!)
TRY THESE………….
•1
•2
•3
•4
•5
H2 + N2 -------> NH3
KClO3 ----------> KCl + O2
Al2O3 -------> Al + O2
Fe + H2O --------> Fe2O4 + H2
Zn + HCl -----> ZnCl2 + H2
Answers for equations…
•1
•2
•3
•4
•5
3H2 + N2 -------> 2NH3
2KClO3 ----------> 2KCl + 3O2
2Al2O3 -------> 4Al + 3O2
2Fe + 4H2O --------> Fe2O4 + 4H2
Zn + 2HCl -----> ZnCl2 + H2
More practice…
•1
•2
•3
•4
Mg + HCl -----> MgCl2 + H2
BaCl2 + H2SO4 -----> BaSO4 + HCl
Li + N2 -------- Li3N
Fe + O2 -------> Fe2O3
Answers…
•1
•2
•3
•4
Mg + 2HCl -----> MgCl2 + H2
BaCl2 + H2SO4 ----> BaSO4 + 2HCl
6Li + N2 -------- 2Li3N
4Fe + 3O2 -------> 2Fe2O3
More practice…
•
Challenge:
• 5 H2O2 -------> H2O + O2
Answers…
•
Challenge:
• 5 2H2O2 -------> 2H2O + O2
Balancing equations
•Balancing act assignment
•Add this to your notes:
•*** combustion reaction products
are carbon-dioxide and water