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Questions and Answers
What does the empirical formula represent in a chemical compound?
What does the empirical formula represent in a chemical compound?
What is the first step in finding the percentage composition of an element in a compound?
What is the first step in finding the percentage composition of an element in a compound?
In determining the molecular formula from the empirical formula, what is the next step after finding the empirical formula?
In determining the molecular formula from the empirical formula, what is the next step after finding the empirical formula?
If a compound has 54.5% carbon, 9.1% hydrogen, and 36.4% oxygen, what do you need to calculate to find its empirical formula?
If a compound has 54.5% carbon, 9.1% hydrogen, and 36.4% oxygen, what do you need to calculate to find its empirical formula?
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What must be done after obtaining the quotient when dividing the MF molar mass by the EF molar mass?
What must be done after obtaining the quotient when dividing the MF molar mass by the EF molar mass?
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Which of the following best describes a physical change?
Which of the following best describes a physical change?
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What evidence indicates a chemical change has occurred?
What evidence indicates a chemical change has occurred?
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Which symbol in a chemical equation indicates a gaseous reactant or product?
Which symbol in a chemical equation indicates a gaseous reactant or product?
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In a combustion reaction, which two reactants are primarily involved?
In a combustion reaction, which two reactants are primarily involved?
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What does the arrow (→) represent in a chemical equation?
What does the arrow (→) represent in a chemical equation?
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Which of the following statements about chemical changes is false?
Which of the following statements about chemical changes is false?
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What is indicated by the symbol (l) in a chemical equation?
What is indicated by the symbol (l) in a chemical equation?
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Which of the following is a characteristic of a chemical change?
Which of the following is a characteristic of a chemical change?
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What is always produced when a substance burns?
What is always produced when a substance burns?
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Which component is NOT part of the fire triangle necessary for combustion?
Which component is NOT part of the fire triangle necessary for combustion?
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What characterizes a decomposition reaction?
What characterizes a decomposition reaction?
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In a single displacement reaction, what happens?
In a single displacement reaction, what happens?
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According to the law of conservation of mass, what statement is true?
According to the law of conservation of mass, what statement is true?
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What does one mole of a substance represent?
What does one mole of a substance represent?
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Which of the following best describes molar mass?
Which of the following best describes molar mass?
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What does percentage composition indicate in a compound?
What does percentage composition indicate in a compound?
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Study Notes
Physical Change
- Matter changes form, but not chemical identity
- Substance remains convertible to its original state
- Examples include melting ice, shredding paper, chopping wood, mixing different colored marbles, cutting a pencil in half
- Properties that change include size, color, shape, and phase
- Chemical identity does not change
Chemical Change
- Chemical reaction occurs, forming new products
- Substance is not convertible to its original state
- Examples include burning wood, rotting a banana, fireworks, cooking food
- Atoms rearrange, forming new substances with significantly different properties from the old ones.
Evidence of Chemical Changes
- Evolution of heat (release or absorption of energy)
- Evolution of gas (bubbles)
- Formation of a precipitate (insoluble solid)
- Change in color
- Change in odor
Chemical Equation
- A shorthand method for representing chemical reactions using symbols and formulas.
Reactants and Products
- Reactants: Substances that react to form new substances (located on the left side of a chemical equation)
- Products: Substances formed from the chemical reaction (located on the right side of a chemical equation)
Symbols Used in Chemical Equations
- +: Separates reactants or products
- → or =: Separates reactants from products, or used in reversible reactions
- (g) or ↑: Indicates a gaseous reactant or product
- (s) or ↓: Indicates a solid reactant or product
- (l): Indicates a liquid reactant or product
- (aq): Indicates a reactant or product in aqueous (water) solution
- Δ: Indicates heat is supplied
Types of Chemical Reactions
Combustion
- Hydrocarbon reacts with oxygen to produce carbon dioxide and water.
- Also known as burning.
- Fire triangle components required: fuel (hydrocarbon), oxygen, and something to ignite the reaction (spark).
Combination/Synthesis
- Two or more substances combine to form a single compound.
- Only one product is formed
Decomposition
- A compound breaks down into two or more simpler substances.
- Only one reactant is present.
Single Displacement
- A single element reacts with an ionic compound, where one element replaces another element in the compound.
Double Displacement
- Ions in two compounds swap partners.
- Cations in one compound combine with anions in the other compound.
Law of Conservation of Mass
- Matter cannot be created or destroyed. The mass of reactants equals the mass of products.
Mole Concept and Conversions
- Mole: The amount of substance containing as many elementary entities as there are atoms in 12 grams of carbon-12 (approximately 6.022 x 1023).
- Molar mass: The mass of one mole of a substance (in grams).
Mole Conversions
- Converting between mass, moles, and the number of atoms/molecules using molar mass and Avogadro's number.
Percentage Composition
- Shows the percentage of each element in a compound.
Empirical and Molecular Formulas
- Empirical Formula: The simplest whole-number ratio of atoms in a compound.
- Molecular Formula: The actual number of atoms of each element in a molecule of a compound.
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Description
Explore the differences between physical and chemical changes in matter in this quiz. Understand key concepts like chemical reactions, reactants, and products, along with evidence of chemical changes and how to write chemical equations. Test your knowledge with examples and definitions to see how well you grasp this important topic in chemistry.
