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Materials for Life
Professor Lynn Cominsky
Joanne del Corral
Sharon Janulaw
Michelle Curtis
July 9, 2003
NBSP Physical Science Leadership Institute
7/9/2003 Prof. Lynn Cominsky 2
Standard Connections Students know properties of solid, liquid
and gaseous substances, such as sugar (C6H12O6), helium (He), and Oxygen (O2), nitrogen (N2) (5)
Students know the common properties of salts, such as sodium chloride (NaCl) (5)
7/9/2003 Prof. Lynn Cominsky 3
First Activity: Sugar and Salt How are sugar and salt different? If we couldn’t taste them, how could we
tell which is which?
7/9/2003 Prof. Lynn Cominsky 4
Sugar and salt investigations:
Given: quantities of sugar & salt, and all the equipment that you have been using during the past two weeks
Can you predict how the physical properties of sugar and salt might differ?
Can you design experiments to differentiate between sugar and salt?
7/9/2003 Prof. Lynn Cominsky 5
Key concepts about Sugar
Sugar is a type of carbohydrate and the most common molecules found in plants and animals
Carbohydrates are literally Carbon that is hydrated Carbon + water
C6H12O6 is glucose Other common sugars:
– sucrose C12H22O11
– fructose C6H12O6
All sugar names end in “ose” as do other carbohydrates
7/9/2003 Prof. Lynn Cominsky 7
Key concepts about Salt In its simplest form, Salt is a molecule
that pairs one element from the first group in the periodic table (e.g., Na) with an element from the seventh group (e.g., Cl)
Group 1 elements have one unpaired electron in their outer shells, while Group 7 elements are missing an electron to complete their outer shells
7/9/2003 Prof. Lynn Cominsky 8
Key concepts about Salt Salts can be formed by mixing an acid
and a base to form a salt and water For example: Hydrochloric acid +
Sodium Hydroxide table salt + water
HCl + NaOH NaCl + H2O In solutions, salt dissociates into Na+
and Cl- ions – Na+ has lost one electron – Cl- has gained one electron
Ionic solutions can conduct current
7/9/2003 Prof. Lynn Cominsky 10
Second activity: Comparing gases
Helium, Nitrogen and Oxygen are all commonly occurring gases
Consult the periodic table to compare the properties of these gases
Can you draw pictures of the structure of each gas?
Consult the materials in your binder to compare the uses of these gases
7/9/2003 Prof. Lynn Cominsky 11
Key concepts: Common gases Helium is a Noble gas – it is the second
most common element in the Universe but is only present in trace amounts in the Earth’s atmosphere
Nitrogen and Oxygen are diatomic gases which are rare in the Universe but – 78% of the atmospheric volume is nitrogen– 21% of the atmospheric volume is oxygen
They are both very chemically reactive
7/9/2003 Prof. Lynn Cominsky 12
Structure of Common Gases:N2
Nitrogen gas is a diatomic molecule formed from two atoms of Nitrogen.
Each atom has 7 electrons. The inner shell is filled with 2 of these electrons, leaving a total of 5
electrons that try to fill the next shell (which holds 8) for each atom. A triple covalent bond between the two nuclei shares 3 pairs of the
electrons. Two other electrons are individually bonded to each nucleus.
7/9/2003 Prof. Lynn Cominsky 13
Structure of Common Gases:O2
Oxygen gas is a diatomic molecule formed from two atoms of Oxygen. Each atom has 8 electrons. The inner shell is filled with 2 of these electrons, leaving a total of 6
electrons that try to fill the next shell (which holds 8) for each atom. A double covalent bond between the two nuclei shares 2 pairs of the
electrons. Four other electrons are individually bonded to each nucleus.
7/9/2003 Prof. Lynn Cominsky 14
Vocabulary Salt: ionic molecule that pairs a group 1
and a group 7 element Sugar: molecule that combines Carbon
with an integral number of water molecules
Ion: elemental form with extra or missing electrons
Noble gas: an element in Group 8, which has a filled outer shell and is chemically (rather) inert
7/9/2003 Prof. Lynn Cominsky 15
ELD Activities: Visual Imagery
Make a slide show, or have images ready to show to the students.
Ask them to first write down on a piece of paper or in their journal whether the object shown is a liquid, a solid, or a gas.
Then ask volunteers to give their answer.
7/9/2003 Prof. Lynn Cominsky 16
Publisher’s Materials
Take some time to look through the state-adopted texts to find activities relating to commonly occurring substances, such as sugar, salt and atmospheric gases
7/9/2003 Prof. Lynn Cominsky 17
Break – something to think about
Why do you think the relative abundances of helium vs. nitrogen/oxygen are so different between the Universe and the Earth’s atmosphere?
7/9/2003 Prof. Lynn Cominsky 18
Standard Connections
Students know atoms and molecules form solids by building up repeated patterns, such as the crystal structure of NaCl or long-chain polymers. (8)
7/9/2003 Prof. Lynn Cominsky 19
Third Activity: Structure of Solids
Given: toothpicks, styrofoam balls Use the toothpicks to represent electrons in
the outer shells Use the styrofoam balls to represent the
nuclei of the various elements Create models for NaCl, Glucose, Nitrogen
gas and oxygen gas Compare the models – what are the structural
differences between Sugar and Salt? Between N2 and O2?
7/9/2003 Prof. Lynn Cominsky 20
Key concepts: Structure of Sugars
Sugars come in many forms– Monosaccharides – glucose, fructose– Disaccharides - sucrose– Polysaccharides – made of many smaller
glucose type rings Polysaccharides include starch,
glycogen and cellulose
7/9/2003 Prof. Lynn Cominsky 21
Structure of Solids: Polymeric Molecules
Starch is made of many units of glucose
Numbered corners are C-H (not shown)
This is (a small part of) amylose 4000 units of glucose
7/9/2003 Prof. Lynn Cominsky 22
Further investigations: Slime!
Given: Borax, white glue, water, food coloring, ziploc bag
Add 1 Tbsp. Borax to 1 cup water, stir until dissolved
Make a solution of ¼ cup water and ¼ cup glue – mix thoroughly
In a ziploc bag, add equal parts borax solution and glue solution
Add a couple of drops of food coloring Seal bag and knead mixture Dig in and have fun!
7/9/2003 Prof. Lynn Cominsky 23
Further questions:
What are the properties of slime? How can we tell that this is a polymer? What other polymers do you know?
7/9/2003 Prof. Lynn Cominsky 24
Key concepts: Structure
Ionic crystals such as salt, have a regular lattice structure
Repeating units in salt are cubic in shape – the molecule is also cubic
Sugars have units that can repeat to make complex carbohydrates such as starch
Repeating units are cyclic in shape – the overall molecule is chain-like
7/9/2003 Prof. Lynn Cominsky 25
Vocabulary
Polymer – complex molecule made of repeating units in a chain-like structure
Crystal – molecular structure made of repeating units in a cubic structure
Saccharide – sweet substance Starch – polysaccharide that is used for
energy storage in plants Glycogen – polysaccharide that is used
for energy storage in animals
7/9/2003 Prof. Lynn Cominsky 26
ELD Activities: Analogies and Student Involvement
Have the students investigate their favorite food and snacks.
Ask them to look at the “Ingredient List” on the label of the food packaging and list all the words ending in “ose” in their journal.
Go over the words with them the next day. (A hint on health awareness might be welcome there as well!)
7/9/2003 Prof. Lynn Cominsky 27
Publisher’s Materials
Take some time to look through the state-adopted texts to find activities relating to structure of common molecules
Examples: MH p. 221
7/9/2003 Prof. Lynn Cominsky 28
Lunch – some things to think about
How do sugars and starches provide energy for plants and animals?
7/9/2003 Prof. Lynn Cominsky 29
Standard Connections Students know how to determine whether a
solution is acidic, basic or neutral (8)
7/9/2003 Prof. Lynn Cominsky 30
Fourth Activity: Cabbage Juice Science
Make your own acid/base indicator by boiling red cabbage.
Use the juice to test whether different fluids are acids or bases.
Compare the pH results from the cabbage juice to those obtained using litmus paper.
7/9/2003 Prof. Lynn Cominsky 31
Equipment for Cabbage Juice activity red cabbage juice vinegar and lemon juice baking soda, powdered lime, and liquid soap some plastic spoons, stirring sticks, and 4 plastic cups 5 medicine droppers 1 marker
7/9/2003 Prof. Lynn Cominsky 32
Cabbage Juice Activity: Label 6 clear plastic cups with numbers 1-6 Fill all cups up ~1/4 of the way with cabbage juice. Collect your five samples
– Vinegar– Lemon juice– Baking soda– Powdered lime– Liquid soap (non-antibacterial)
Place a small amount of each sample into each of five of the plastic cups.
If your sample is an acid, it will turn the cabbage juice pink. If your sample is a base, it will turn the cabbage juice green.
7/9/2003 Prof. Lynn Cominsky 33
Further investigations:
Label 2 clear plastic cups: 1 and 2 Fill all cups up ~1/4 of the way with water. Place one known acid and one known base
into each of the cups. Place a piece of litmus paper into each of the
cups. Basic solutions will turn red litmus paper blue
and will leave blue litmus paper unaffected. Acidic solutions will turn blue litmus paper red
and will leave red litmus paper unaffected.
7/9/2003 Prof. Lynn Cominsky 34
Key concepts: pH
Acidic solutions contain an excess of protons or H+. pH is a measure of how 'acidic' a solution is. The lower the pH, the more acidic the solution.
In chemical terms, pH means "the negative log of the concentration of protons" in solution. Chemistry students should recognize this as pH = -log[H+].
7/9/2003 Prof. Lynn Cominsky 35
Key concepts: pH
"Neutral" solutions (e.g.,water) have a pH of 7. This number coincides with the amount of H+ naturally formed in water from the equilibrium reaction:
H2O H+ + OH- "Basic" solutions have a pH greater
than 7, meaning that they have less free H+ than that in neutral water.
7/9/2003 Prof. Lynn Cominsky 36
Key concepts: pH Red cabbage contains pigments call
anthocyanins. The pigments give it the red/purplish color. Anthocyanins belong to group of chemical compounds called flavonoids.
Other plants that contain anthocyanins include beets, cranberries and blueberries.
7/9/2003 Prof. Lynn Cominsky 37
Vocabulary pH: A measure of the acidity or alkalinity of a
solution, numerically equal to 7 for neutral solutions. The pH scale commonly in use ranges from 0 to 14.
Base: Any of a class of compounds whose aqueous solutions are characterized by a bitter taste, a slippery feel, the ability to turn litmus blue, and the ability to react with acids to form salts.
Acid: Any of a class of substances whose aqueous solutions are characterized by a sour taste, the ability to turn blue litmus red, and the ability to react with bases and certain metals to form salts.
7/9/2003 Prof. Lynn Cominsky 38
ELD Activities: Visual imagery and student involvement
Form groups of 14 students. Have all students wear an “H+ sign”. Draw a circular boundary (one per
group) on the ground and ask each group to make “acidic, neutral, or basic solutions” by adding, or removing “H+s (represented by each student) using the pH scale as a reference.
7/9/2003 Prof. Lynn Cominsky 39
Publisher’s Materials
Take some time to look through the state-adopted texts to find activities relating to pH, acids and bases.
Examples: HM p. C78
7/9/2003 Prof. Lynn Cominsky 40
Break – some things to think about
Do you think pH would be a useful test to discriminate between sugar and salt?
Why or why not?
7/9/2003 Prof. Lynn Cominsky 41
Standard Connections Students know living organisms and most
materials are composed of just a few elements (5)
7/9/2003 Prof. Lynn Cominsky 42
Fifth Activity: Essential elements in living organisms
Review the handout in the binder that includes many tables summarizing the elemental abundances in different locations
How many elements are essential to plants? To animals?
How do the abundances change from the Universe to the solar system?
7/9/2003 Prof. Lynn Cominsky 43
Fifth Activity: Essential elements in living organisms
How do the abundances change from the solar system to the atmosphere?
How do the abundances change from the atmosphere to the oceans?
How do the abundances change from the oceans to the crust?
How do the abundances change from the crust to plants?
7/9/2003 Prof. Lynn Cominsky 44
Further investigations:
What do these changes tell you about the evolution of life in the Universe?
7/9/2003 Prof. Lynn Cominsky 45
Key concepts: Essential Elements
Light elements (H and He) dominate the early Universe
As the solar system formed, heavier elements (made in stars) were incorporated to make the planets
The atmosphere is about ¾ N2 and ¼ O2
There are a limited number of elements that are essential to plants and animal life, including H, C, N and O.
7/9/2003 Prof. Lynn Cominsky 47
ELD Activities: Compare and Contrast Table A
Write down examples of living organisms. Remember you are a living organism!
Find or draw a picture of the living organisms you found
List all elements this organism or material needs in order to survive (i.e. water)
7/9/2003 Prof. Lynn Cominsky 48
ELD Activities: Compare and Contrast Table B
Write down examples of materials
Find or draw a picture of the materials you found
List all elements this organism or material needs in order to keep form (i.e. Carbon)
7/9/2003 Prof. Lynn Cominsky 49
Questions for ELD Tables:
1. Using table A and B, list the common elements you see in living organisms and materials:
2. What does this tell you about living organisms and
most materials? Are they similar in any ways?
7/9/2003 Prof. Lynn Cominsky 50
Publisher’s Materials
Take some time to look through the state-adopted texts to find activities relating to the elements that are essential to plants and animals
7/9/2003 Prof. Lynn Cominsky 51
Take away – brain teaser
What do you think the gases are that make up the atmospheres of the “gas giant” planets such as Jupiter and Saturn?
7/9/2003 Prof. Lynn Cominsky 52
Lesson Study Activities
Identify a key concept from today’s lecture for further development
Review the publisher’s materials about this key concept
Think about the best way to present this key concept in your classroom
7/9/2003 Prof. Lynn Cominsky 53
Resources
Physics by Inquiry – L. McDermott and the PEG at U Washington
http://www.saltinstitute.org/15.html http://www.brooklyn.cuny.edu/bc/ahp/SDPS/SD.PS.ions.html http:// biology.clc.uc.edu/graphics/ bio104/glucose%20alone.jpg
http://www.greenspirit.org.uk/resources/glucose.gif http://www.elmhurst.edu/~chm/onlcourse/chm110/molimages/N2.GIF
http://www.poemsinc.org/oceano/abund.htm