Chemistry Exam Notes on Amino Acids and Hydrocarbons
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Questions and Answers

What aspect should be avoided when presenting scientific evidence in a description?

  • Focusing on irrelevant information (correct)
  • Including key vocabulary
  • Using multiple sources
  • Integrating historical data

Which best describes the effective use of key vocabulary in scientific descriptions?

  • It should blend into irrelevant details.
  • It must only contain technical jargon without context.
  • It should be loosely integrated with general statements.
  • It is used precisely to describe scientific principles. (correct)

How should conclusions in scientific discussions be formulated?

  • By generalizing the data presented.
  • Focusing solely on past models.
  • Demonstrating practical applications of evidence and claims. (correct)
  • Only stating the results without application.

What component is essential when discussing scientific theories and models?

<p>Integrating extended focus on definitions and principles. (C)</p> Signup and view all the answers

Which of the following represents a requirement for effective scientific communication?

<p>Focus on concrete details relevant to claims. (B)</p> Signup and view all the answers

What is the primary purpose of filtration in the context described?

<p>To separate mixtures containing an undissolved solid in a liquid. (B)</p> Signup and view all the answers

Which question would the authors find least important for understanding the problem of water contamination?

<p>Why did Flint switch from Detroit’s water supply to the Flint River? (A)</p> Signup and view all the answers

Which method is most effective for separating a precipitate from water?

<p>Filtration (B)</p> Signup and view all the answers

What do lead ions form when sulfate ions are added to contaminated water?

<p>A solid precipitate. (A)</p> Signup and view all the answers

What is the likely consequence of adding sulfate ions to the water in the described context?

<p>The creation of a visible precipitate. (B)</p> Signup and view all the answers

Why is chromatography not the best method for separating lead from the water?

<p>It cannot effectively separate solid precipitates from liquids. (C)</p> Signup and view all the answers

Which statement about the separation techniques is correct?

<p>Filtration operates by removing solids through a barrier. (D)</p> Signup and view all the answers

What are the health effects of being exposed to toxic metals in water considered to be?

<p>Severe and can lead to chronic health issues. (D)</p> Signup and view all the answers

Which statement accurately describes the relationship between mass and volume?

<p>Mass and volume have a direct relationship (A)</p> Signup and view all the answers

Using Graph 1, what is the missing volume value in Table 1?

<p>3.5 mL (D)</p> Signup and view all the answers

What is the calculated density of the unknown metal?

<p>2.6 g/mL (A)</p> Signup and view all the answers

Based on the Table of Densities, which metal is most likely used in the coins?

<p>Aluminum (D)</p> Signup and view all the answers

Which statement about the particle models of aluminum, lead, and lithium is true?

<p>Model A is more dense than Model C. (A)</p> Signup and view all the answers

What is a true statement regarding the phase change of boiling water?

<p>The temperature of the boiling water remains constant. (B)</p> Signup and view all the answers

Which phase of matter corresponds to the particle diagram with the least amount of energy?

<p>Solid (C)</p> Signup and view all the answers

Which statement correctly describes the behavior of carbon dioxide in soda manufacturing?

<p>Carbon dioxide is stored as a liquid in high-pressure tanks. (B)</p> Signup and view all the answers

What does the symbol (aq) in a balanced chemical equation represent?

<p>Solution (D)</p> Signup and view all the answers

Which compound is identified as the cloudy precipitate in the reaction?

<p>Copper (II) hydroxide (B)</p> Signup and view all the answers

What indicates that heat was produced in a chemical reaction?

<p>The temperature increased significantly. (A)</p> Signup and view all the answers

Why is it beneficial for the scientist to wait for one hour before observing the reaction again?

<p>It enables the solid precipitate to settle for clear observation. (D)</p> Signup and view all the answers

Which of the following describes the language that should be used in formal writing?

<p>Precise and formal language (C)</p> Signup and view all the answers

What type of expression is recommended for persuasive writing?

<p>Persuasive and clear expression (D)</p> Signup and view all the answers

In a scientific report, what should be ensured regarding sources?

<p>Sources should be explicitly cited with precision. (C)</p> Signup and view all the answers

What is a key characteristic of subject-specific language in scientific writing?

<p>Technical vocabulary tailored to the audience (D)</p> Signup and view all the answers

Which statement best describes the relationship between cysteine and selenocysteine?

<p>Cysteine contains sulfur while selenocysteine contains selenium. (D)</p> Signup and view all the answers

Which statement correctly compares the atomic radii of selenium and sulfur?

<p>Selenium has a larger atomic radius than sulfur due to more electron shells. (B)</p> Signup and view all the answers

Which molecule is likely to be more polar, cysteine or selenocysteine?

<p>Selenocysteine is more polar because selenium is more electronegative than sulfur. (C)</p> Signup and view all the answers

How many total electrons does a neutral atom of magnesium (Mg) have?

<p>12 (C)</p> Signup and view all the answers

How many valence electrons does a neutral atom of magnesium (Mg) possess?

<p>2 (C)</p> Signup and view all the answers

Which of the following Lewis dot diagrams accurately represents a neutral fluorine atom?

<p>7 dots (A)</p> Signup and view all the answers

Which diagram most likely depicts the strongest type of intermolecular force?

<p>Diagram showing hydrogen bonding (C)</p> Signup and view all the answers

How many amino acids were originally identified before the discovery of selenocysteine?

<p>20 (D)</p> Signup and view all the answers

Which set of conditions best keeps carbon dioxide in a liquid phase?

<p>6900 kPa and -54 ℃ (B)</p> Signup and view all the answers

Why is it important for the student to stir the mixture in water before filtering?

<p>Stirring helps dissolve the soluble NaCl into the water. (A)</p> Signup and view all the answers

What material is collected on the filter paper after the filtration process?

<p>river rock particles (B)</p> Signup and view all the answers

Which statement does not support the identification of the material on the filter paper?

<p>River rock particles and salt can go through the filter paper. (B)</p> Signup and view all the answers

What is the total mass of the filtered river rock salt sample after evaporation?

<p>240.0 g (B)</p> Signup and view all the answers

Which of the following statements accurately describes the function of the filter paper?

<p>It allows soluble substances to pass while retaining insoluble substances. (D)</p> Signup and view all the answers

What is the primary reason for evaporating the water from the filtered solution?

<p>To separate the dissolved salt for analysis. (B)</p> Signup and view all the answers

What does the solubility table indicate about NaCl compared to AgCl?

<p>NaCl is more soluble than AgCl. (A)</p> Signup and view all the answers

Flashcards

Amino Acid Comparison

Selenocysteine and cysteine differ in their chemical composition. Cysteine contains sulfur (S), while selenocysteine has selenium (Se).

Atomic radius of Selenium vs Sulfur

Selenium has a larger atomic radius than sulfur. This is because selenium has more electron shells.

Polarity of Cysteine and Selenocysteine

Selenocysteine is likely more polar. This is because selenium is more electronegative than sulfur, creating a greater electronegativity difference.

Magnesium electrons

A Magnesium (Mg) atom has 12 total electrons and 2 valence electrons.

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Fluorine Lewis Dot Diagram

The correct Lewis dot diagram for a neutral fluorine atom should show seven dots surrounding the fluorine symbol.

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Strongest Intermolecular Force

To determine the strongest intermolecular force, identify the type of bond or force present in the diagram.

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Magnesium (Mg) Total Electrons

A neutral Magnesium atom has 12 total electrons.

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Magnesium (Mg) Valence Electrons

A neutral Magnesium atom has 2 valence electrons.

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Filtration

A method to separate a solid from a liquid by passing the mixture through a filter.

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Separation of lead ions

Lead ions in water can be separated by adding sulfate ions, which form a precipitate (a solid) with lead.

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Filtration to separate contaminate

Used to separate a precipitate (solid formed in the water mixture) from a liquid, such as water contaminates lead ions from water

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Precipitate

A solid that forms when two substances in a solution react

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Chromatography

Method for separating mixtures based on differences in how substances travel through a medium.

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Distillation

Method to separate liquids with different boiling points, by heating and condensing.

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Evaporation

Method for separating a solid from a liquid by heating to vaporize the liquid.

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Aqueous mixture

A mixture containing a dissolved substance (solute) in water (solvent).

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Mass-Volume Relationship

Mass and volume have a direct relationship—as one increases, typically so does the other.

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Density of Unknown Metal

Density is mass divided by volume; use provided data to calculate a metal's density.

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Metal Identification

Compare calculated density to known densities of possible metals in a reference table to identify the substance.

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Density Comparison

Density of an object is a measure of how tightly packed its particles are; higher density means more mass in a smaller volume.

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Boiling Point of Water

The temperature of water stays constant when it boils, not increasing or decreasing.

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Phase of Matter and Energy

Different phases of matter (solid, liquid, gas) correspond to different amounts of energy contained. Solids have the lowest energy, followed by liquids, and then gases.

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Storing Carbon Dioxide

Compressed carbon dioxide, usually in a liquid form, occupies far less volume than gaseous form, making storage easier.

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Carbon Dioxide Phase Diagram

A graphical representation showing the phases of carbon dioxide (and conditions corresponding to each phase) under varying temperatures and pressures.

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Scientific Principles

Basic laws and theories in science that explain how the natural world works.

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Evidence

Data, observations, or facts that support or refute a scientific claim.

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Claim

A statement that a scientist makes based on evidence and reasoning.

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Integrating Multiple Sources

Combining information from various sources (like research papers, experiments, and historical data) to understand a concept.

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Real-World Applications

How scientific principles and knowledge can be used to solve problems or improve our lives.

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Conditions for Liquid CO2

High pressure (e.g., 6900 kPa) and low temperature (e.g., -54°C) are needed to keep carbon dioxide in a liquid state.

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Solubility of NaCl

Sodium chloride (NaCl) is soluble in water, meaning it dissolves in water.

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Insoluble River Rocks

River rock particles are insoluble in water; they do not dissolve in water.

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Stirring in Mixture

Stirring a mixture of soluble and insoluble substances helps the soluble substance dissolve more readily and evenly distributes the substances.

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Filtering a Mixture

Filtering separates substances based on particle size. Larger particles are trapped, while smaller ones pass through.

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Material Collected on Filter Paper

Insoluble materials (like river rock particles) are collected on filter paper during filtration.

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Why Stir Before Filtering

Stirring ensures the soluble substance (like salt) dissolves completely before filtering, preventing it from being collected with the insoluble matter.

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Correct Reason for Stirring

Stirring helps dissolve the soluble substance (e.g., salt), making it easier to separate from the insoluble material (e.g., rocks).

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What does (aq) represent?

(aq) represents a substance dissolved in water, meaning it's in an aqueous solution.

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What is a precipitate?

A precipitate is a solid that forms from a chemical reaction in a solution.

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How does temperature indicate heat?

A temperature increase means heat was produced during the reaction. A decrease indicates cold was produced.

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How does time help observe products?

Waiting allows the solid precipitate to settle, making it easier to observe the products of the reaction.

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Balanced chemical equation

A balanced chemical equation shows the exact number of atoms of each element present in the reactants and products of a chemical reaction.

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What is a cloudy precipitate?

A cloudy precipitate is a solid that forms during a chemical reaction and appears as a cloudy substance suspended in the solution.

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What is a reaction?

A reaction is a process that involves the rearrangement of atoms and molecules to form new substances.

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What are the sources of information?

The sources of information for answering the questions can be found in the Lab Reaction tab, Data Table tab, and Reference Sheet tab.

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Study Notes

Chemistry Exam Notes

  • Amino acids are the essential building blocks of life. 20 were originally identified, with cysteine containing sulfur. Selenocysteine, discovered in the 1950s, increased the total to 21.
  • Selenocysteine and cysteine are similar in structure but selenocysteine has selenium instead of sulfur.
  • Cysteine's sulfur atom and selenocysteine's selenium atom influence their atomic radii, and thus their chemical properties. Selenium's larger atomic radius is due to more electron shells.
  • Different compounds have different boiling points based on their intermolecular forces.
  • Strong intermolecular forces lead to higher boiling points due to increased energy needed to overcome the attractions between molecules.
  • Methane, ethene, and fluoromethane are examples of hydrocarbons.
  • Methane contains single bonds, ethene a carbon-carbon double bond, and fluoromethane does not contain a triple bond.
  • Each carbon atom in hydrocarbons forms four bonds.
  • All of these compounds are nonpolar in nature.
  • More massive samples of substances require longer times for temperature changes and phase changes. Larger amounts of heat are required to increase the temperature of a sample with larger mass, which also translates to more time required for the same temperature increase.
  • The freezing point of a substance on a cooling curve is the point at which a liquid substance is in the process of changing to a solid.
  • The temperature remains constant during the phase change in a cooling curve.
  • Filtration separates a solid from a liquid. A solution of solid and liquid substances is put on a filter, keeping the solid out of the liquid (solution).
  • Distillation separates liquids with different boiling points. The liquid with the lower boiling point boils first, and then the liquid with the higher boiling point boils.
  • Evaporation is a separation technique that separates a liquid from a solid that is dissolved in the liquid. The liquid evaporates, leaving the solid behind.
  • The law of conservation of mass states that in any chemical reaction, the total mass of the substances involved remains constant.
  • The mass of the materials should remain the same before and after any chemical reaction and/or separation process.

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Description

This quiz covers essential concepts in chemistry, focusing on amino acids, particularly cysteine and selenocysteine, and their significance in biology. The notes also explore the properties of hydrocarbons and the impact of intermolecular forces on boiling points. Test your knowledge and understanding of these fundamental topics in chemistry.

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