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Questions and Answers
Which of the following is NOT evidence of a chemical change?
Which of the following is NOT evidence of a chemical change?
- Change in shape (correct)
- Change in color
- Release of energy
- Formation of a precipitate
According to the kinetic molecular theory, what causes chemical reactions to occur?
According to the kinetic molecular theory, what causes chemical reactions to occur?
- The constant motion of particles leading to collisions (correct)
- The electrostatic attraction between particles
- The force of gravity acting on particles
- The presence of a catalyst
What is the difference between a chemical change and a nuclear change?
What is the difference between a chemical change and a nuclear change?
- Chemical changes involve the formation of new molecules, while nuclear changes involve the formation of new elements. (correct)
- Chemical changes are always reversible, while nuclear changes are not.
- Chemical changes involve the rearrangement of atoms, while nuclear changes involve the rearrangement of subatomic particles.
- Chemical changes only occur at high temperatures, while nuclear changes can occur at any temperature.
What is Avogadro's number, and what does it represent?
What is Avogadro's number, and what does it represent?
When writing a chemical equation, why is it important to balance the equation?
When writing a chemical equation, why is it important to balance the equation?
Flashcards
Chemical Changes
Chemical Changes
Processes resulting in new substances with different properties.
Physical Changes
Physical Changes
Changes where the chemical composition remains unchanged.
Avogadro's Number
Avogadro's Number
6.02 x 10^23 particles (molecules) in one mole of any substance.
Evidence of Chemical Change
Evidence of Chemical Change
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Writing Chemical Equations
Writing Chemical Equations
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Study Notes
Chemical Changes
- Physical/Phase Changes: These changes do not alter the chemical composition of a substance. No new chemicals are formed.
- Chemical Changes: New substances with different properties are formed in these changes.
Nuclear Changes
- Elements transformed: Nuclear changes involve elements being changed into different elements.
- Fission/Fusion: Examples of nuclear changes include fission and fusion reactions.
Why Reactions Occur
- Kinetic Molecular Theory: The smallest particles of matter are in constant, random motion.
- Collisions: These particles collide with each other.
- Rearrangement: Collisions can lead to the rearrangement of particles, forming new substances.
Evidence of Chemical Changes
- Color Change: A noticeable shift in color suggests a chemical change.
- Odor Change: A change in smell indicates a chemical reaction.
- Precipitate Formation: The formation of a solid (precipitate) within a solution signals a chemical reaction.
- Energy Changes: Chemical reactions often release or absorb energy. This is categorized as endothermic/exothermic.
Avogadro's Number
- Particle Count: Avogadro's number (6.02 x 1023) represents the number of particles (molecules) in one mole of a substance.
- Molecules vs. Moles: Distinguish between the number of molecules and the unit moles.
- Conversion: Use Avogadro's number to convert between the number of particles and amount of moles.
Writing Chemical Equations
- Reactants & Products: A chemical equation must identify the reactants and products.
- Correct Elements: Ensure the equation contains the correct chemical symbols for each element.
- Balanced Charges: The overall charge on both sides of the equation must be balanced.
- Equal Elements: The number of atoms of each element must be equal on both sides of the equation.
- States of Matter: Include the physical state of each substance (e.g., solid, liquid, gas). Examples for states are added below.
- Examples of Equation Components:
- magnesium + hydrochloric acid → magnesium chloride + hydrogen gas
- hydrogen + oxygen → water
- iron (II) nitrate + sodium phosphate → sodium nitrate + iron (II) phosphate
- solid silicon tetrachloride + water → gaseous silicon dioxide + hydrochloric acid
- phosphoric acid + calcium sulfate → calcium phosphate + sulfuric acid
- aluminum + fluorine → aluminum fluoride
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