Chemical Reactions Overview
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Questions and Answers

What happens during a combustion reaction?

  • Two molecules interact to form a single molecule.
  • A single reactant breaks down into multiple products.
  • Oxygen combines with a compound to form carbon dioxide and water. (correct)
  • Water and salt are produced.

    • How is a synthesis reaction defined?

  • It is a reaction where a reactant produces heat.
  • Two or more substances combine to form a new compound. (correct)
  • It involves the breakdown of a compound into simpler substances.
  • It occurs between an acid and a base to form water and salt.

    • Which of the following statements regarding balancing chemical equations is true?

  • Reactants can have different types of atoms than products.
  • Balancing is only needed for combustion reactions.
  • You can change the subscripts to balance a chemical equation.
  • The number of atoms of each element must be equal on both sides. (correct)

    • What type of reaction occurs during the burning of a candle?

    <p>Combustion</p> Signup and view all the answers

    What does an acid-base reaction typically produce?

    <p>Water and salt</p> Signup and view all the answers

    What are substances that react with one another called?

    <p>Reactants</p> Signup and view all the answers

    Which of the following is NOT a sign of a chemical change?

    <p>Melting ice</p> Signup and view all the answers

    What is the term for the substances produced by a chemical reaction?

    <p>Products</p> Signup and view all the answers

    How is an exothermic reaction characterized?

    <p>Heat is released</p> Signup and view all the answers

    Which of the following processes is an example of a chemical change?

    <p>Cooking an egg</p> Signup and view all the answers

    Which of the following statements best describes a physical change?

    <p>The original substance can be regained</p> Signup and view all the answers

    What happens to old bonds in reactants during a chemical reaction?

    <p>They are broken</p> Signup and view all the answers

    Which of the following reactions requires energy input to proceed?

    <p>Photosynthesis</p> Signup and view all the answers

    Study Notes

    Chemical Reactions

    • Chemical reaction: Substances react to form new substances with different chemical properties.

    Definitions

    • Reactants: Substances that react with each other.
    • Products: Substances formed from the reaction.
    • Chemical change: A reaction that forms new products.
    • Physical change: A change in state (phase) without changing the chemical form.

    Parts of a Chemical Reaction

    • Reactants are the starting substances.
    • Products are the substances formed in the reaction.
    • Example: 2H₂(g) + O₂(g) → 2H₂O(l)
      • Reactants: 2H₂ (g) , O₂(g)
      • Product: 2H₂O(l)

    How to Tell if a Chemical Reaction is Taking Place

    • Color change
    • Gas production (bubbles, fizzing)
    • Temperature change (heat or cold)
    • Formation of a precipitate (solid forming from a liquid)
    • Smell

    Examples of Chemical Changes

    • Burning wood
    • Rotting fruit
    • Baking a cake
    • Rusting metal
    • Using a battery
    • Digestion
    • Souring milk
    • Exploding fireworks
    • Cooking an egg
    • Photosynthesis

    Class Activity

    • Examples of chemical changes.
    • Signs of chemical change for each example.

    Homework

    • Page 48 classify substances.
    • Revision exercise question 1-4.
    • Complete balancing equations worksheet.
    • Research examples of exothermic and endothermic reactions on page 55

    Chemical Change

    • Chemical change: New products are formed when old bonds break and new bonds form between products, resulting in a new product/molecule.
    • Example: Rust

    Phase Change

    • Physical change: When a substance changes phases (solid, liquid, gas) the molecule remains the same, and it can return to its original form.
    • Example: Water changing to steam

    Energy Changes

    • Exothermic reactions: More energy is given out than is required. Energy is lost to the surroundings, and the product is colder than the reactants.
    • Example: Burning a candle
    • Endothermic reactions: More energy has to be put in than is given out. Energy is taken from the surroundings, and the product is warmer than the reactants.
    • Example: Baking bread

    Types of Chemical Reactions

    • Combustion
    • Synthesis
    • Acid-base reactions
    • Decomposition

    Combustion

    • Oxygen combines with a compound to form carbon dioxide and water.
    • Example: Fuel + O₂ → CO₂ + H₂O

    Synthesis

    • Two molecules interact to form a different molecule.
    • Example: A + B → AB

    Acid-Base Reactions

    • A chemical reaction between an acid and a base forms water and a salt.
    • Example: Acid + Base → H₂O + Salt

    Decomposition

    • A reactant breaks down into two or more products.
    • Example: AB → A + B

    Balancing Chemical Equations

    • The number of atoms of each element must be the same on both sides of the equation.

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    Related Documents

    Chemical Reactions PDF

    Description

    This quiz covers the fundamental concepts of chemical reactions, including definitions of reactants and products, the distinction between chemical and physical changes, and indicators of a chemical reaction. Explore various examples and learn to identify when a chemical reaction occurs.

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