Transcript Welcom Back - University of Arizona

NATS 101 :
“The World We Create”
•Welcome Back!
•Remember Project 2 Due
TODAY!
3/23
Where Were We?
In Unit 2 we discussed environmental change,
including natural and man-made effects.
We talked about how some of the substances we
put into the atmosphere are negatively
affecting our environment.
Ozone
Depletion
Global
Warming
Acid Rain
Unit 3:
New materials,
to build or to waste?
Today we start Unit 3! Let’s talk about how
we are positively impacting our environment
Petroleum
We have seen that petroleum is used
primarily for two things:
Power Generation
Materials Synthesis
Used to fuel many
things, from cars, to
furnaces, to
electricity generation.
Used to make a variety
of products/materials
84%
Petroleum use
16%
Petroleum use
Ink
What are some things made
Dishwashing liquids
Paint brushes
Telephones
from petroleum?
Toys
House paint
Movie
film
Car sound insulation
Tires
Motorcycle helmets
Heart
valves
Refrigerator linings
• Plastics
Insecticides
Antiseptics
Fishing lures
Deodorant
• Cosmetics Linoleum
Sweaters
• Fertilizer/ Insecticide
Paint rollers
Floor wax
• Rubber Products
Shoes
Electrician's tape
Plastic wood
Toothpaste
Glue
•
AND
MORE
Food preservatives
Trash bags
Soap dishes
Skis
Permanent press clothes
Hand lotion
Clothesline
Dyes
Soft contact lenses
Shampoo
Panty hose
The Challenge
How do you get from this
CHEMICAL REACTIONS!!
to these?
Today’s Expected Outcomes
Recognize and describe the
characteristics of a chemical reaction;
Describe and follow the necessary
steps to synthesize a useful product;
Recognize materials that have
positively impacted our environment.
Chemical Reaction? You decide
Number your paper 1-10. Designate whether the situation
describes a chemical reaction
Keep your paper,
(True) or does not (False)
we will revisit these
at the end of class.
1. Rubbing alcohol evaporating from surface of your skin
2. Burning a candle
3. Melting a sugar cube
4. Cooking an egg
5. Freezing water (liquid water turning to ice)
6. A photographer’s flash blub flashing
7. Leaving a wagon outside to rust
8. Accidentally spilling bleach on your favorite jeans
9. Taking a few TUMS after a particularly spicy dinner
10. Butter melting on warm toast
Chemical Reaction? You decide
Let’s examine a few more examples;
jot down some quick notes:
What is happening in the video?
What does the process start with and what does it
end with?
Does this represent a chemical reaction?
Why or why not?
Videos:
Reaction or No Reaction?
What is a Chemical Reaction?
Use information and rules you used to distinguish
chemical reactions from non-reactions in the
True/False activity, as well as the information you’ve
gathered from the videos to answer this question.
Discuss your ideas with your teammates . . .
Think about . . .
How you decided what was truly a chemical
reaction and what was not?
What characterizes a chemical reaction?
Chemical Reactions: Definition
-A shuffling or rearrangement of chemical
building blocks (atoms)
-Leads to the formation of products that
have different properties than the
reactants used to create them.
Reactants: all substances that react
during the change
Products: all substances produced
after the change
Chemical Reactions: Representation
Space Filling Models
Ball and Stick Models
Words:
Magnesium wire + oxygen gas  magnesium oxide
Letters and Symbols
2Mg(s) + O2(g)  2MgO(s)
Chemical Reactions:
Representation
Some important facts to consider
• Atoms are not created or destroyed in a chemical
reaction; molecules may be broken apart and
recombined to form new molecules
• The molecules on either side of a reaction arrow may
not be the same (nor do they have to be)
* All atoms on one side of the equation must be equal
to those on the other, the same number of each type
of atom must appear on both sides of the equation
2 Mg(s) + O2(g)  2 MgO(s)
Chemical Reactions:
A Closer Look
AgNO3(aq) +KCl(aq)  AgCl(s)+KNO3(aq)
Can you describe what is happening in this
reaction?
Can you detect a pattern?
Displacement Reaction: reactants change
partners to create new products
A Closer Look:
Displacement Reactions
AgNO3(aq) +KCl(aq)  AgCl(s)+KNO3(aq)
Who are the players?
Ag+, (NO3)- , K+, Cl-
-
+
+
+
-
-
+
-
+
-
+
What
happens
when we
mix
them?
Displacement Reactions
AgNO3(aq) +KCl(aq)  AgCl(s)+KNO3(aq)
How do they change partners?
AgNO3(aq) +KCl(aq)  AgCl(s) + KNO3 (aq)
+
+
-
-
+
-
+
+
-
-
+
+
-
In General: MN +PQ  MQ + PN
+
-
Let’s Examine:
Displacement Reactions
• Follow the directions on the handout in order to
experiment with displacement reactions.
• Be sure to record:
– Observations of the reactants before you combine
them, and products after you combine them (i.e.
what do they look like)
– The chemical formulas of the reactants you are
combining.
• Attempt to write the full chemical equation of each
reaction
**Remember in a displacement reaction: MN + PQ  MQ + PN
Results: What did you see?
A+B:
K2CO3(aq) + K3PO4(aq)  K3PO4(aq) + K2CO3(aq)
(clear liquid)
(clear liquid)
(clear liquid)
A+C: K2CO3(aq) + CuCl2(aq)  2 KCl(aq) + CuCO3(s)
(clear liquid)
(blue liquid)
(blue solid)
A+D: K2CO3(aq) + CoCl2(aq) 2 KCl (aq) + CoCO3(s)
(clear liquid)
(red liquid)
PRECIPITATES
(purple solid)
Results: What did you see?
B+C: 2K3PO4(aq) + 3CuCl2(aq)  6KCl (aq) + Cu3(PO4)2(s)
(clear liquid) (blue liquid)
(dark blue solid)
B+D: 2K3PO4(aq) + 3CoCl2(aq)  6KCl(aq) + Co3(PO4)2(s)
(clear liquid)
(red liquid)
(dark blue solid)
C+D: CuCl2(aq) + CoCl2(aq)  CuCl2(aq) + CoCl2(aq)
(blue liquid)
(red liquid)
(gray liquid)
How do we know there was a
chemical reaction?
Based on our results and all of the reactions we
have seen, how do we know a chemical reaction
has happened?
• Color change
• Formation of a precipitate: an insoluble product
• Energy is released (in the form of heat, light, etc. we
have seen these is the past, do you remember what
they are called?)
We often see the effects of a chemical reactions in the
difference between the reactants and products.
Final Component of Chemical Reactions
We were able to merely combine reactants and observe a reaction,
this isn’t always the case. Can you think of any reason why not?
Necessary Conditions . . .
Temperature: more energy in the system = more collisions*
Pressure: more pressure mean less space for molecules to move around =
more collisions
Concentration: more molecules to react = more collisions
Presence of a Catalyst: a compound that in some way effects the progress of a
chemical reaction, without being changed or consumed in the reaction
All of these are components of a set of carefully
controlled conditions, required to effectively generate the
desired products, and are collectively called
Reaction Conditions
Creation of New Materials
Scientist manipulate the products of chemical
reactions (usually many reactions in many steps) to
create useful products.
Scientists use what they know about chemical
reactions, reactants and products to design and
synthesize products to meet particular needs.
New Materials
We can break the creation of new materials into 3
steps:
Design
Synthesis
Processing
Let’s examine these 3 ideas in terms of the precipitate
we made in the previous displacement reactions.
K2CO3(aq) + CoCl2(aq)  2 KCl(aq) + CoCO3(s)
(clear liquid)
(red liquid)
(purple solid)
We’ve created a
pigment that can be
used to color many
different materials
New Materials: Design
When designing new materials what considerations
might scientists need
to think about?
Objectives: What are we trying to make, what
purposes do we need to accomplish, yield, product
purity
What could we make with our pigment?
Limitations: Costs (equipment and raw materials),
space, safety, environmental impact, reliability (of
equipment and process), flexibility (in design and
process)
New Materials: Synthesis
What do we mean by the word synthesis?
In terms of synthesis, what might scientists need
to think about when creating new materials?
Scientists often consider. . .
-the specific reactants and sequences of
reactions that can be utilized in order to
create the desired products
-the best set of reaction conditions to
maximize the yield.
We’ve already synthesized the pigment
K2CO3 + CoCl2  CoCO3 + 2KCl
New Materials: Processing
What additional steps need to be
accomplished in order to create a
useful product?
Products must often be:
- separated (i.e. centrifugation)
- filtered
- distilled
- purified
- combined with additional
materials
What about our
Pigment?
•Separate out of
solution
•Transform it from a
powder to a useful
product
Creating a Product: It’s your turn!
You and your group members are going to become
chemical engineers
You must process this pigment, in order to create a
useful paint product.
•
•
•
•
•
•
Directions:
Each group of 3 students will receive the
following supplies:
1 gram of pigment (CoCO3)
1 small vial of Linseed Oil (solvent)
1 mL pipette (for measuring the oil)
1 plastic teaspoon (for measuring the pigment)
“Paintbrush” to test your paint
1 plate to perform experiments on
Creating a Product: It’s your turn
YOUR TASK: Using these supplies, work with
your group to determine the ratio of pigment
to oil that yields the “best” paint.
Be Prepared to:
• Define what “best” means to your
group; (i.e. dries the fastest, has the
deepest color, etc.)
• Share your recipe for the best paint
What did you produce?
• What was your best product?
• What was the recipe for that
product?
You’ve taken raw materials (pigment) and
transformed them into paint, what are some
other materials that have transformed your
world?
Drastic Transformations:
Materials that have changed our world
• Medication/Pharmaceuticals
• Agrochemicals
• Plastics and Elastomers
(You’ll learn more about these on Thursday!)
• Fuels
• Detergents (soaps, shampoos,
cleaners)
• Flavorings
Chemical Reaction?: You decide
Let’s revisit our list
Number your paper 1-10.
Designate whether the situation describes a chemical
reaction (True) or does not (False)
1. Rubbing alcohol evaporating from surface of your skin False
2. Burning a candle True
3. Melting a sugar cube False
4. Cooking an egg True
5. Freezing water (liquid water turning to ice) False
6. A photographer’s flash blub flashing True
7. Leaving a wagon outside to rust True
8. Accidentally spilling bleach on your favorite jeans
9. Taking a few TUMS after a particularly spicy dinner
10. Butter melting on warm toast
False
True
True