1 Unit 3: Matter Look around you. What do you see? In front of you are all kinds of stuff- all sorts of matter. Some of this matter you can see, and there’s more that you can’t. Some substances, such as those in your body, are undergoing transformations as we speak. And most of it is all mixed together, which complicates things further. What’s it all made out of? It’s a big mess. What we need to make sense of it is a way to sort things out. Our primary goal for this unit is to classify the matter that is all around us. First, we’ll consider what we can say about mixtures. As you might guess, not very much…it varies from sample to sample. So, we will explore some purification techniques. We will spend the remainder of our time finding out what we can about pure substances- these are the materials that the universe as we know it is made from. And since nearly all understanding of matter begins with pure substances, purification is the first step in chemical research. Here’s the plan: Lesson 1: Introduction to matter. Classifying mixtures. Separation techniques. Lab: Separation Experiment pre-lab. Lesson 2: Pure matter and it’s properties. Lab: Separation Lab. Lesson 3 States of matter. Liquid crystals and plasmas. Lab: Chromatography. Lesson 4: Review for Matter test. Lab: Complete chromatography lab. Lesson 5: Matter test. How do we find out what everything is made out of?
Transcript
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Unit 3: Matter
Look around you. What do you see? In front of you are all kinds of stuff- all
sorts of matter. Some of this matter you can see, and there’s more that you
can’t. Some substances, such as those in your body, are undergoing
transformations as we speak. And most of it is all mixed together, which
complicates things further. What’s it all made out of? It’s a big mess. What
we need to make sense of it is a way to sort things out.
Our primary goal for this unit is to classify the matter that is all around us. First, we’ll consider
what we can say about mixtures. As you might guess, not very much…it varies from sample to
sample. So, we will explore some purification techniques. We will spend the remainder of our time
finding out what we can about pure substances- these are the materials that the universe as we
know it is made from. And since nearly all understanding of matter begins with pure substances,
purification is the first step in chemical research.
Here’s the plan:
Lesson 1: Introduction to matter. Classifying mixtures. Separation techniques.
Lab: Separation Experiment pre-lab.
Lesson 2: Pure matter and it’s properties. Lab: Separation Lab.
Lesson 3 States of matter. Liquid crystals and plasmas. Lab: Chromatography.
Lesson 4: Review for Matter test. Lab: Complete chromatography lab.
Lesson 5: Matter test.
How do we find out what everything is made out of?
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2Unit 3 Dr. B.’s ChemAdventure Matter
What is matter? Anything that hasand occupies
1. What is it? 2. Mixtures: types 3. Mixtures: purification3. Pure matter and it’s properties 4. States of matter 5. Liquid crystals
massspace
What is everything made out of? matter
How do we find out what everything is made out of? We need to Classify it
Separation Lab 10 Points Chemists typically spend more than half of their time purifying substances- separating them into their individual pure components. In this lab you will be given a mixture of 5 solid ingredients. Typically, these are sand, sugar, salt, iron filings, corn kernels, and pebbles. This year, they are:
Your goal is to separate all ingredients of your mixture quantitatively, and analyze your results. You will be graded based on your choice of methods, your report, and how close your amounts are to the actual amounts provided. Tonight: Discuss this with your partner and come up with a plan. Write it as a diagram below. You are welcome to use any equipment in the lab as long as you work safely and have it approved by me. Be ready to begin your experiment the following day. You will be allowed to dry any wet samples overnight. Note that no student has yet come up with a quantitative method to separate salt from sugar. Sample Separation Scheme
sand
sand
sugarsalt
Method
pebbles
Iron filings
sugarsalt
pebbles
Iron filings Method
Methodsugarsalt
pebbles
Iron filings
sugar
salt
Iron filings
Iron filings salt
Method
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Most common errors: -No separation or only partial separation of salt and sugar. -Samples still wet after overnight drying.
1. Homework: Draw a neat diagram showing how you will separate the mixture, using the same
general format as the scheme shown on the previous page.: Approval stamp: 2. In class: Receive your approval stamp on the bottom of the previous page. Get your mixture. 3. Record the total mass of your mixture: _______ g. Begin your experiments! Record your procedure and observations below. Be sure a stranger could repeat your procedure. The following day, record your results: 4. What are the masses of each separated component? (You will be allowed one day for drying if any of your samples are wet).
Total Mass:________ 5. Based on the mass of your starting mixture and total mass of isolated ingredients What is your % error? 6. What is the likely source of your % error? 7. Analysis. Write a paragraph summarizing your experiment, and reflect on the results. Be sure to include recommended improvements if you were to repeat the process. Use additional paper if necessary.
The universe as we know it has about 100 elements. Occasionally we see them in their isolated form- for example an engagement ring may be pure gold (Au), with a diamond on it, which is pure carbon (C ). More often we see the elements combined to form molecules, such as water (H2O) or table salt (NaCl). Sometimes called compounds, molecules are made out of multiple elements which are bonded together and they have constant physical properties. For example, water freezes at 0 oC, and table salt melts at about 2000 oC. If we look closely at the things around us, we find that most of them are mixtures of molecules. Drinking water, for example, is mostly made out molecules of water, but also has some molecules of salts (like NaCl) and may have added fluoride as well. Classify each of the materials below as an element, molecule, or mixture. The examples below should help get you started. It’s OK if you miss a few…this is to get us thinking about what things are made out of. A key will be passed out after you complete this. Element, molecule, or mixture? A. Silver
Answer: Silver is an element (Ag). B. Air
Answer: air is a mixture of nitrogen (an element), oxygen (an element), and, among other things, carbon dioxide (a molecule).
C. Ice Answer: ice the solid form of water, which is a molecule (H2O).
Classify the 19 materials on the next page, then check the answer key to see how you did.
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Element, molecule, or mixture?
Material Element? Molecule? Mixture? A. Silver B. Air C. ice 1. Mud 2. sugar 3. steam 4. Baking soda 5. Alumninum foil 6.brass 7. blood 8. Bubble gum 9. gatorade 10. chalk 11. glass 12. Soy sauce 13. grasshopper 14. gasoline 15. urine 16. snow 17. milk 18. tobacco 19. Pencil lead (graphite)
20. Look around you. Try to find examples of elements, molecules, and mixtures in front of you right now.
1. An element in front of me right now is _____________ 2. A molecule in front of me right now is_____________ 3. A mixture in front of me right now is____________
After you have completed this, we will discuss the answers and provide you with a key.
Introduction to Matter and Purification Worksheet 1. The essential question that we will be asking all year is:________________________ _____________________________? 2. This unit on matter is our first chance to take a shot at answering it. Our first observation is that most of the matter around us is not pure- it is a _____________ of substances. Air for example is a mixture of many substances, including nitrogen, oxygen, and carbon dioxide. 3. What is a heterogeneous, and what is a homogeneous mixture? 4. In this room I see wood, glass, aluminum foil, water, a cup of coffee, and tortilla chips. Describe each as a pure substance, a homogeneous mixture, or a heterogeneous mixture. 5. Give two examples of liquid-solid homogeneous mixtures: Suggest a method for isolating:
6. Pure water from drinking water 7. Individual ink pigments from a magic marker 8. Salt from salt water 9. Oxygen from the air
10. What is the difference between an element and a substance?
11. In order to understand what everything is made out of, all mixtures must be separated into their individual substances. Why?
Pre-lab: Please read the introduction and answer the questions. Introduction New England is famous for its dramatic fall foliage. Every fall “leaf peepers” come from all over the country to witness the explosion of colors the blanket our Connecticut landscape. Some years are bright and bold, others muted and sublime. Every year is different, and every leaf is different. Our goal is to isolate and identify the individual chemicals that create this show. Today after school collect some fall leaves. We will analyze them the following day. Background: Light is a form of electromagnetic radiation. The different colors of light we see are a combination of many reflected wavelengths that vary from 380 - 750 nm (nanometers) in length. Each wavelength also has a specific amount of energy measured in particles, called photons. In general, shorter wavelengths have more energy than longer ones. Every leaf contains hundreds if not thousands of individual chemicals. We’ll focus on three visible groups with characteristic fall colors: the carotenes, xanthophylls, and chlorophylls. Their chemical structures and typical colors are shown on the following page.
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Leaf Pigments
Carotenes: Gold to Orange
O
O Xanthophylls: Light Yellow
NN
N
O
O
O
N
O O
Mg
Chlorophyll A: grass green
Mg
ON
N
O
O
N
N
O
O
O
H
Chlorophyll B: Olive Green
We can separate the different pigments found in leaves by using paper chromatography. First we’ll mush up the leaves in ethanol to dissolve the chemicals. Then we’ll spot the solutions on some paper,
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and put them in a jar that contains some solvent and let the solvent rise up the paper, separating the chemicals based on how strongly they adhere to the paper. Reading a chromatogram The distance your chemical travels up the paper is called it Rf value. If it didn’t move at all if has a value of zero. If it went as high as the solvent did it that is a value of 1. Here is a spot with a Rf value of about 0.75:
* CAUTION: The leaf extract and the chromatography solvent contain aromatic organic solvents. It is very important that you do not breathe the fumes from the solvent. Be very careful with this solvent and wash your hands thoroughly after this exercise. The leaf extract will stain clothes. Do not spill either the leaf extract or the chromatography solvent. If there is an accidental spill, notify your instructor immediately. In this lab we will isolate the four substances shown on page 2. For those drawings to make sense, included in this pre-lab is a brief lesson on: Reading chemical structures Chemical drawings of carbon-based molecules are usually written in a form known as shorthand notation, based on the following rules:
a. Most contain H, O, N, and C, where hydrogen tends to form one bond, oxygen two, nitrogen three, and carbon forms four bonds (HONC if you love chemistry). b. Carbon atoms are not drawn. Instead, any bend or end of a line indicates a carbon atom. c. Hydrogen atoms are also left out. It’s easy to know how many hydrogen atoms are attached because of the HONC rule. See the examples. d. Atoms other than carbon or hydrogen are included in the chemical structure. e. A more detailed type of drawing molecules called bond notation is also used, where every atom is drawn.
The examples on the next page show how this is done: Examples: Ethyl alcohol is drawn in shorthand notation as:
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OH
Which we can re-draw using bond notation as:
OH
H HH
H HC
C
Note that the HONC rule is obeyed: each hydrogen atom has one bond, oxygen two, and carbon four. Here’s another molecule known as tetrahydrofuran, shown in shorthand and bond notation
OH
HH
H HHH
HOC
CC
C
shorthand notationfor tetrahydrofuran
bond notationfor tetrahydrofuran
Note that tetrahydrofuran has 4 carbons, 8 hydrogens, and one oxygen: it has a molecular formula of C4H8O. Pre-lab questions 1. Complete the following table by filling in the four rectangular areas:
H
H H
H H
H H
HHH
N
molecule shorthandnotation
bondnotation
molecularformula
cylohexane C6H12
butane CC
CC
pyridineC5H5N
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2. Here are the typical Rf values of a leaf chromatogram: Molecule Rf value
Carotenes 0.8 Xanthophylls 0.7 Chlorophyll A 0.5 Chlorophyll B 0.45
Draw what your leaf chromatogram should look like tomorrow, identifying each spot, and use a colored pencil to indicate it’s color.
3. Draw beta-carotene using bond notation below, and give its molecular formula. (The shorthand notation for this molecule is on page 2). Tomorrow, bring to class several leaves of a known type. Draw your leaf here and identify the common name of the plant:. Common Plant Name ____________________________. That completes the pre-lab. _________________________________________________________________________ Leaf Chromatography: Procedure: Your lab instructor will demonstrate how to prepare your leaf sample and chromatograph it. (Instructors: use about two mL of acetone for dissolving leaf in mortar and pestle, and use 95% hexanes/5% acetone for chromatography solvent: all 4 bands can be separated using this procedure. Attach your chromatogram and identify the location and Rf values of the carotenes, xanthophylls, chlorophyll A, and chlorophyll B.
Wordbank (not all of the words are in this story) Crystalline Amorphous Matter Substance Compound Solid Gas Heterogeneous Homogeneous Liquid crystal Liquid Sublimation Deposition Boiling Melting Condensation Chemical Physical Silicon Oxygen Ozone Precise accurate
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While walking down the beach one day, I spied a small object. I noticed it has both mass and took up space, so I was sure it was ___________. I picked it up and took a look at it under a magnifying glass. I could not see any impurities in this glassy object, therefore I was pretty sure it was _____________________. I assumed it was pure, so I classified it as a ____________________. I took it home and heated it over a fire, but it did not melt, so I can’t really say anything about that __________________(physical, chemical) property. I hammered it and it did not flatten; it is not _____________. I tried to stretch it and could not; it is not _______________. This material is a colorless solid. By the way, The other states of matter are ___________, _____________, and _____________. A few believe that _____________ represent a fifth state of matter, and this phase could either be in a ____________ or _____________ state. My little rock is just a simple solid. Since it is shiny I could say it is ___________. If I had the right equipment I could heat it up to a liquid (_________ it), or perhaps even heat it further from a liquid to a gas (_______________). It’s possible that when I heat it up it might go directly to a gas (_______________), but I doubt it. I do know that iodine vapors can cool directly to form a solid (_______________), but that has nothing to do with my story. I happened to have some hydrofluoric acid kicking around, and when I dropped in my substance to that nasty acid, it dissolved. That _____________(physical, chemical) change was weird. I sent it out to an analysis lab and they told me that my 600 milligram sample consisted of 280 milligrams of Si (_______________), and the rest was O (_______________). The percent composition of my sample is therefore _______% Si, and ________% O. And I thought my substance was a pure element, but really it is a just a _________. I submitted several similar samples I found at the beach and they all gave exactly the same analysis; this data is very ___________. I assume the people at the lab know what they are doing so it is probably __________ as well.
My substance is______________.
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Howtoaceitunit3
How to ace the Matter quiz
Be able to provide detailed answers to the questions below. Have a thorough understanding of the concepts below. Be able and ready to separate a mixture if given
one. 1. What is matter? Matter is_____________________ 2. What is a substance? A substance is a __________ _________ or ____________ 3. What is a physical property? 4. What is a chemical property? 5. How could I separate sand from aluminum powder? 6. What are the states of matter? 7. Where can I observe plasma? 8. What are liquid crystals? 9. What are the two types of liquid crystals and how do they differ? 10. Describe the six conversions of matter states (boiling, melting…) 11. What is the law of conservation of mass? 12. Define malleable and ductile and give examples of each. 13. Heterogeneous mixture = ___________________; homogeneous mixture =___________________
Homogeneous mixtures can be solid/liquid (______________), liquid/liquid (______________), gas/liquid (______________), gas/gas (______________), or even solid/solid (______________).
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14. How to separate mixtures
a. Sugar from sand b. Iron from sand c. Water from the ocean d. Blue ink from black ink
15. What is an element? 16. What is a compound? 17. Why is chromatography such a powerful method for the separation of chemical mixtures? 18. Draw a chromatogram of a sample that has a Rf of 0.75 19. What does HONC mean? 20. Draw methanol, CH4O, using both bond and shorthand notation 21. Draw butane, C4H10, using both bond and shorthand notation…can you assemble it another way? 22. What is the periodic table?
