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 carbon-dioxide 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

Element/Compound Reactant or Product? State of Matter

Fe Reactant Crystalline solid

O2 reactant Gas

Fe2O3 Product Crystalline solid

Fe (cr) + O2 (g) Fe2O3 (cr)

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 → H2O + NaCl

• 2. Zn + HCl → 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 H2 + N2 -------> NH3

•2 KClO3 ----------> KCl + O2

•3 Al2O3 -------> Al + O2

•4 Fe + H2O --------> Fe2O4 + H2

•5 Zn + HCl -----> ZnCl2 + H2

Answers for equations…

•1 3H2 + N2 -------> 2NH3

•2 2KClO3 ----------> 2KCl + 3O2

•3 2Al2O3 -------> 4Al + 3O2

•4 2Fe + 4H2O --------> Fe2O4 + 4H2

•5 Zn + 2HCl -----> ZnCl2 + H2

More practice…

•1 Mg + HCl -----> MgCl2 + H2

•2 BaCl2 + H2SO4 -----> BaSO4 + HCl•3 Li + N2 -------- Li3N •4 Fe + O2 -------> Fe2O3

Answers…

•1 Mg + 2HCl -----> MgCl2 + H2

•2 BaCl2 + H2SO4 ----> BaSO4 + 2HCl•3 6Li + N2 -------- 2Li3N •4 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