ai huynh_LAB1_Liquid Density

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Chemistry

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Feb 20, 2024

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Spring 2024 1 CHEM 1474-E01 Chemistry for Everyday LAB 1: SCIENTIFIC METHOD/LIQUID DENSITY MEASUREMENT Spring 2024 <General guideline for all labs> • Read course syllabus to know our lab policy. • All communication should be done via school email (xxxx@ucdenver.edu). • The work will be submitted through canvas assignments in PDF only. You can simply upload pdf files under each “Lab report” assignment tap. • Please complete embedded questions before you return your lab reports. • Pay attention to grading rubric in canvas and also grader’s comments not to repeat same mistake. • There is no late submission. Pay attention to the due date. • Significant figures and units will be graded always. All work should be clearly shown for all questions. This means that you have to show your solution for calculation question. • Zoom office hour is not for experiment demonstration. If you have any question about the lab report, please do not hesitate to contact me. ( kyoung.kim@ucdenver.edu ). • You can share lab materials with your classmates to save your budget. However, sharing any part of lab report (answer, picture, and etc.) will be considered as cheating. Please be advised our syllabus to know the consequences/policies of cheating in this class.

Spring 2024 2 Student Full Name: Ai Huynh Student ID: 110426649 Date of performance: 01/29/24 I. Title: SCIENTIFIC METHOD/LIQUID DENSITY MEASUREMENT II. Purpose: 1. Learn how to measure mass and volume in a chemistry laboratory. 2. Understand the intrinsic nature of density and how density is defined III. Material: Sugar (~110g), water (~210ml), kitchen balance, syringe or straw, food color and Pyrex measuring cup (any size) IV. Introduction: 1) Mass (m, grams): a measure of a quantity of matter in a body. 2) Volume (v, milliliters): the amount of space a body occupies in three dimensions. 3) D ensity (ρ): the ratio of the mass of an object to its volume (eq 1). LINK: MASS VOLUME AND DENSITY Ρ (density) = mass/volume = g/ml Eq 1.1 4) Solute: Substance which is dissolved (Fig 1). 5) Solvent: Substance that dissolves solute. 6) Solution: homogeneous mixture of two or more substances. LINK: SOLUTE, SOLVENT AND SOLUTION Fig 1. Density explains the ratio of the mass of solute in a certain volume of solution. 7) Atomic Mass (Fig 2): A mass of atom that is expressed in atomic mass unit (AMU or g/mol). Usually, atomic mass is equal to the sum of number neutrons and protons. LINK: Atomic mass (khan academy)

Spring 2024 3 Fig 2. Bohr model (left) and atomic symbol (right) of carbon element. Carbon includes 6 neutrons (yellow balls) and 6 protons (red balls) and atomic number is assigned based on the number of protons (number 6 on the top of carbon symbol C). Atomic mass is assigned with the sum of number of protons and neutrons. For carbon, atomic number is 12.0107 g/mol (bottom number of Symbol C) 1 8) Mole: The number of substances, such as element, molecule, ions and etc. 1 mole includes Avogadro’s number ( 6.023 × 10 23 ) of substances. LINK: mole (Avocadro’s number and stoichiometry) V. Graded Pre-lab Questions: 1. Please answer the following questions before you start lab. (2 pts each) 1) If there is a large mass in a small volume, is the value of the density large or small. Explain. Answer: If there is a large mass in a small volume, the density is large. It’s because density is defined as mass per unit volume. When the mass is large and the volume is small, the mass is concentrated in a small space, resulting in a high density. In simpler terms, there's a lot of stuff (mass) packed into a small area (volume), making the density high. 2) When the mass of object is reduced half and the volume of solution is doubled, what happens to the density and why? (Hint: Eq 1) Answer: When the mass of an object is reduced by half and the volume of a solution is doubled, the density decreases. This happens because density is calculated by dividing mass by volume. When the mass is halved, but the volume is doubled, the ratio of mass to volume decreases, resulting in a lower density. In simpler terms, there's less stuff (mass) in the same amount of space (volume), so the density decreases. 3) When the balloon is filled with Helium (He), it floats, but not with Oxygen (O 2 ) in it. Why? Assume those gasses filled in the same volume. (Hint: atomic mass of He=4.003g/mol and atomic mass of O=32g/mol, respectively. How does this atomic mass affect the density of gas?) 1 https://www.livescience.com/28698-facts-about-carbon.html

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Spring 2024 4 Answer: When the balloon is filled with helium (He), it floats, but not with oxygen (O2) in it because helium has a lower density than oxygen. Density is determined by the mass of gas particles per unit volume. Helium atoms have a much lower atomic mass than oxygen molecules. Since helium atoms are lighter, they occupy more volume for the same mass compared to oxygen molecules. Therefore, when the balloon is filled with helium, it contains fewer gas particles per unit volume, resulting in a lower density and causing the balloon to float. Conversely, when the balloon is filled with oxygen, the higher density of oxygen molecules causes it to sink because there are more gas particles per unit volume, making it denser and heavier than the surrounding air. 4) You measured out 45.0 mL of dense liquid. Its mass is 63.3 g. What is the density of this liquid? Show your work and consider significant figures for your answer. (HINT: Eq 1) Answer: 63.3g/45.0mL = 1.406667g/mL = Density 2. Categorize the following examples (a-f) into “Solute”, “Solvent”, and “Solution” (1 pt each) (a) (b) (c) (d) (e) (f) Salt Water Gatorade Coffee Rice Vinegar Sugar 1) Solute: A) Salt, E) Rice Vinegar, F) Sugar 2) Solvent: B) Water 3) Solution: C) Gatorade, D) Coffee VI. Lab Procedure: LINK: DENSITY MEASUREMENT LAB PROCEDURE HINT: The rainbow stack may not be perfect. It continuously mixed up, so it is not giving nice rainbow color. This could happen due to chemicals in food coloring. It could mass up with density of sugar solution. I suggest you add food coloring as little as possible. You may also increase amount of sugar but same proportional. If it does not work either way, it is really ok to take a picture of your dark solution. I do not take points off for imperfect result. I do still count your time and work. You may still need to discuss about imperfect result. Why it happened and how the result could be improved in the future. Please do not hesitate to contact me if you have any question. 1. Prepare 4 empty and clean glass cups (100 ml capacity). 2. Add different amount of sugar in each cup respectively. (ex. 10g, 20, 30, and 40g) 3. Add 50 ml of warm water in each cup and stir the solution until sugars completely dissolves. If you are

Spring 2024 5 having hard time to dissolve sugar completely, please microwave them for short time (roughly 30 sec). 4. Add 2-3 drops of different food color into 4 cups respectively. (Ex. 10g-red, 20g-yellow, 30g-green, 40g-blue) 5. In a new/clean glass cup (100 ml capacity), add 10ml of solution one by one carefully, starting from 40g (blue) of sugar solution at the bottom. You may use either syringe (recommended) or straw. Please be advised by video below. 6. Keep in mind that the layers might not be perfectly stacked due to food coloring that you are adding. If this happens please try 3g (red), 30g (yellow), and 60 g (blue) of sugar to give bigger density gap. VII. Graded Observations: 1. Insert the picture of final product with your name together and briefly explain what you observed. (2 pts) - 2 pts for not having picture with student’s name on it. Ex. In the sugar water rainbow experiment, I tried doing this experiment 4 times, yet I still fail I the end. However, I do believe there are several reasons to why the experiment ended up as a failure for me. Firstly, the experiment requires a precise sugar gradient with solutions of gradually increasing sugar concentrations. I did tried to start from one spoon of sugar and continue to 4 spoons of sugar, but it still look like the sugar measurement is too close together. Secondly, careful layering is crucial; since I didn’t have a syringe, I tried using a spoon and a straw to carefully put the layers together, but they always ended up mixing. Thirdly, the type of food coloring used might be problematic. The food coloring, I used is in a gel, which is thicker than liquid food coloring and

Spring 2024 6 could affect the dispersion in the sugar water, leading to less clear and distinct layers. Lastly, I did tried to put little of food coloring as possible according to the recommendation, but it still didn’t work so I wonder the type of food coloring is the real problem for this experiment to fail for me. 2. Shake the solution and observe whether the solution recover color layer in certain amount of time or not and explain why Take a picture of layer before you shake!!!! (2pts) Answer: Since I failed at the experiment, the color remained the same as the picture above as the color already mixed before I shake the solution. I believe that shaking the solution would only further mix any of the remaining unmixed food coloring or sugar, but it wouldn't change the overall color of the solution. It looks like the shaking process simply distributes the components more evenly throughout the solution, but it does not alter the color that has already been achieved by the initial mixing of the food colorings. VIII. Graded Post lab Calculation: Calculate the density of each solution. Show your work. (2pts each) 1. 10g sugar in 50ml water: 10g+50g/50mL = 60g/50mL = 1.2g/mL = Density 2. 20g sugar in 50ml water: 20g+50g/50mL=70g/50mL= 1.4g/mL = Density 3. 30g sugar in 50ml water: 30g+50g/50mL=80g/50mL= 1.6g/mL = Density 4. 40g sugar in 50ml water: 40g+50g/50mL=90g/50mL= 1.8g/mL = Density IX. Graded Analysis/Discussion:

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Spring 2024 7 1. Briefly explain your observation based on the calculation above. (2pts) Answer: Based on the calculations above, I can see that as the amount of sugar (solute) dissolved in the water (solvent) increases, the density of the solution also increases. This indicates that the concentration of the solution is increasing as more sugar is added, leading to a higher density. Therefore, there is a direct relationship between the mass of the solute and the density of the solution. 2. What is the major force (interaction) that is involved in water (H 2 O) and Sugar (C 12 H 22 O 11 ) interaction? What makes sugar dissolve in water? Research on the following Wiki page and write your answer in full sentence. If you refer to textbook/online resources other than wiki page provided below, please reference the source. (2pts) LINK: Non-covalent interaction LINK: Cite reference in ACS style Answer: The major force involved in the interaction between water (H2O) and sugar (C12H22O11) is hydrogen bonding. Hydrogen bonding occurs between the hydrogen atom of water molecules and the oxygen atoms of sugar molecules. This interaction allows sugar molecules to dissolve in water, as the hydrogen bonds between water and sugar molecules are strong enough to overcome the attractive forces within the sugar molecules themselves, causing them to separate and disperse evenly throughout the water. This information is supported on the Wiki page on "non-covalent interaction". X. Graded Conclusion: Explain all the concepts and vocabulary that were used in the lab in detail. This should be at least a ½ page statement that answers the questions posed in your purpose. Avoid personal feelings and emotions. (2pts) In this laboratory experiment, several key concepts and vocabulary terms were utilized to understand the measurement of mass, volume, and density. Firstly, mass was defined as the measure of the quantity of matter in a body, typically expressed in grams. Volume, on the other hand, represented the amount of space occupied by an object in three dimensions, commonly measured in milliliters. Density, denoted by the symbol ρ, was introduced as the ratio of an object's mass to its volume, as described by the equa tion ρ = mass/volume. The purpose of the experiment was to learn how to measure mass and volume accurately in a chemistry laboratory setting, and to comprehend the intrinsic nature of density and its definition. Throughout the experiment, various materials were utilized, including sugar, water, a kitchen balance, a syringe or straw, food coloring, and a Pyrex measuring cup. Additionally, key terms such as solute, solvent, and solution were employed to describe different components of mixtures. A solute was defined as the substance being dissolved, while the solvent was the substance that dissolved the solute. A solution, on the other hand, referred to a homogeneous mixture of two or more substances. These concepts were illustrated using a graphical representation of density and its relationship with the mass of solute in a certain volume of solution. Furthermore, the lab explored the concept of atomic mass, which represented the mass of an atom expressed in atomic mass units

Spring 2024 8 (AMU or g/mol). The atomic mass of elements, such as carbon, was discussed in the context of their Bohr models and atomic symbols, illustrating the relationship between protons, neutrons, and atomic mass. The concept of a mole, defined as the number of substances such as elements, molecules, or ions, was also introduced, with one mole containing Avogadro’s number (6.023 × 10^23) of substances. Overall, the laboratory experiment provided a comprehensive understanding of mass, volume, and density, along with the associated vocabulary and concepts essential for conducting experiments and analyzing results in a chemistry laboratory.