CHEM 100 Lecture Notes - Lecture 1: Intensive And Extensive Properties, Metalloid, Boron

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chocolatesardine697

24 Oct 2017

School

UWM

Department

Chemistry and Biochemistry

Course

CHEM 100

Professor

Dr.Carlson

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Document Summary

Basic terms part i: a property is a description of something. An example of this is: color, taste, odor (a) a(n) intensive property is one which does not change with sample size. (b) a(n) extensive property is one which does change with sample size. An example of this is: mass, length, volume (c) a(n) physical property is one which describes the look, touch, feel or general. An example of this is: water freezing or evaporating appearance of something. It also describes a physical change for something. itself or something else. Resistance to corrosion intensive physical property extensive property physical change intensive physical property chemical property. Give two elements which belong to this category: iron and nickel: a non-metal has the general properties of non-conductive, brittle, and gas or liquid (in the standard state). Give two elements which belong to this category: hydrogen and neon: a semi-conductor is a(n) metalloid.

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I need help doing my lab homework, I missed lab that day because, I was sick and it's due.

Chemical Reactions and Equations Learning objectives To observe physical and chemical properties associated with chemical changes To be able to give evidence for the occurrence of a chemical reaction To write a balanced chemical equation To identify areaction as a combination, decomposition, precipitation, single or double replacement, or combustion reaction ntroduction When a substance undergoes a physical change, it changes its appearance but not its composition. For example, when ice melts to form water, it undergoes a physical change from solid to liquid. In a chemical change, the composition of a substance is changed to give a new substance with different physical and chemical properties. For example, when silver tarnishes, the shiny silver (Ag) changes to a dull gray silver sulfide (AgaS). Not only has the chemical formula changed from Ag to Agus, but also the physical properties (shininess) of the substance have changed. Some examples of physical and chemical changes are listed in Table 1 below. Table 1. Comparison of Physical and Chemical Changes Examples of Physical changes Examples and Evidence of Chemical Changes Change in state (melting, freezing, evaporating Formation of a gas (bubbles) subliming) Formation of a solid (precipitate) Change in size Tearing Change in Color Heat is given off or absorbed A solid dissolving in a solvent In a chemical reaction, atoms in the reactants are rearranged to produce new combinations of atoms in the products. However, the total number of atoms of each element in the reactants is equal to the total number of atoms in the products. This is true according to the Law of Conservation of Mass, which states that the total mass remains constant during a chemical reaction. In other words, matter cannot be created or destroyed in a chemical reaction. In a chemical equation, the reactants are shown on the left and the products are on the right. An arrow in between indicates that a chemical reaction occurs. Finally, the physical state of each compound is designated in parentheses after the chemical formula. Solid, liquid, gas, and aqueous (dissolved in water) are shown as(s,(n,(g), and (aq), respectively.

Chromatography: Separating Mixtures

Introduction:

Magic marker inks are often mixtures of several compounds. Paper chromatography is a common method of separating various components of a mixture. After separation, you can observe the different colors that make up a particular color of magic marker ink.

You can also calculate a ratio Rf, which compares how far each compound traveled to how far each solvent (substance that dissolves another substance) traveled during the experiment.

Rf = Ds/Df

Ds = Distance traveled by the compound

Df = Distance traveled by the solvent

Materials:

coffee filter, tape, isopropyl alcohol (rubbing alcohol), water, 3 different color magic markers (not permanent); 3 identical tall, narrow drinking glasses; metric ruler, 3 pencils

Pre-lab Questions:

List one extensive and one intensive property of marker ink.

Intensive: Amount Doesn't Matter

Extensive: Amount Matters

An extensive property of marker ink would be volume or ink.

An intensive property of marker ink would be the color of ink.

Define mixture.

A combination of two or more substances that are not chemically combine with one another.

Is tap water a heterogeneous or homogenous mixture? Explain your answer.

Tap water is a homogeneous mixture. I think this because I can see that it has uniform. It doesnât contain any different molecules as well.

Is isopropyl alcohol (rubbing alcohol) a heterogeneous or homogenous mixture? Explain your answer.

I believe rubbing alcohol is a homogeneous mixture. I think this because I can physically see that it has uniform. It also stays in the same phase.

Procedure:

1. Cut 3 strips of coffee filter. Be sure that the strips are much narrower and slightly taller than the drinking glasses.

2. In the center the strips, about 3 cm from one end, place a dot of the marker to be tested. The dots should be about 0.2 cm in diameter and dark enough to be clearly visible.

3. Place about 2 cm of water in each glass.

4. Tape the unmarked end of each strip to the center of a pencil so that the strip hangs down when the pencil is held horizontally.

5. Carefully insert the strips into the glasses, dotted end down. The dot must be above the water, and the sides of the coffee filters cannot touch the sides of the glasses.

6. Let the setup stand for 20 minutes. Follow procedure 8 as your set up stands.

7. Record your observations after 20 minutes in the table below. Measure Df (in cm) for the solvent. Measure the Ds (in cm) for each color that you see on the coffee filter (there may not be three). Calculate the Rf for each color using the equation in the Introduction section.

8. Repeat steps 1â7, except place about 2 cm of isopropyl alcohol (rubbing alcohol) in each glass instead of water.

9. Clean up your work area.

Solvent: isopropyl alcohol (rubbing alcohol)

5. What evidence is there that marker ink is a mixture?

The marker ink is a mixture. The evidence is when the marker ink separated.

6. Each compound in the marker ink is represented by a color. Did one compound travel farther than the others? Explain why you think that this is the case.

Yes, I found out that the darker of the three colors traveled further.

7. Did the compounds travel farther in the water or the isopropyl alcohol (rubbing alcohol)? Explain why you think that this is the case.

The compounds traveled faster in the water than the rubbing alcohol. I think the reason why is because water is smaller on a molecular level versus rubbing alcohol. So it is easier for the dyes to separate.

8. How could you improve upon the accuracy of your Rf measurements?

I feel that accuracy could be improved if we changed the scale measurement to millimeters (mm) instead of cm (centimeters).

Water traveled faster than the rubbing alcohol. I personally think it has to do with something like the size of the molecule like the smaller the molecule the easier it is.

21. If you have one gram of each of the following metals, which one would you expect to heat up the fastest? A) Silver B) Lead C) Aluminum D) Iron 22. If it requires 67 J of heat to r aise the temperature of a pi ece of iron by 5.0 o C, calculate the mass of the iron. The sp ecific heat of iron is 0.46 J/g o C. A) 150 g B) 100 g C) 29 g D) 706 g 6 Lab Quiz # 2, 3 23. Inside a typical calorimeter the sample releases energy and heat flows into the water. In order to calculate the speci fic heat of an unknown metal, which of the following measurements must be made? A) Mass of the unknown metal, mass of the water, initial tempera ture of the metal, final temperature of the water B) Mass of the unknown metal, mass of the water, initial tempera ture of the metal, initial and final tempe ratures of the water C) Mass of the calorimeter, initial temperature of the metal, in itial and final temperatures of the water D) Mass of the calorimeter, mass of the water, initial and final temperatures of the water 24. In lab a student builds an a luminum âtentâ around the calori metry apparatus. The purpose of the âtentâ is to A) cause the system to heat up. B) allow heat to escape into the surroundings. C) limit the amount of oxygen in the system. D) prevent too much loss of heat to the air. 25. Specific heat can be used, a long with other observations, to determine the identity of a substance because it is A) a physical property. B) a chemical property. C) a measure of heat. D) both a physical and a chemical property. 26. During an experiment to determin e the specific heat of a met al, the student did not fully immerse the hot metal object in t he water bath. How would this error change the calculated specific heat? A) The calculated specific heat would be too low because not all of the heat is transferred to the water. B) The calculated specific h eat would be too high because not al l of the heat is transferred to the water. C) The calculated specific heat would be too high because the ma ss submerged is low. D) The calculated specific heat would be unchanged because it is not dependent on the heat transferred

CHEM 100 Lecture Notes - Lecture 1: Intensive And Extensive Properties, Metalloid, Boron

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