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Questions and Answers
What indicates that a chemical reaction has taken place?
The new substance formed in a chemical reaction is called a reactant.
False
What is the word-equation for the reaction of magnesium with oxygen?
Magnesium + Oxygen → Magnesium oxide
The substances that undergo chemical change are called ______.
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Match the substances with their categories:
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Which of the following is NOT a type of observation that indicates a chemical reaction?
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The arrow in a word-equation indicates the transition from products to reactants.
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What is produced when magnesium burns in oxygen?
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What are the products of the decomposition of ferrous sulphate when heated?
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Thermal decomposition reactions require heating to occur.
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What does the thermal decomposition of calcium carbonate produce?
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Heating ferrous sulphate results in the emission of _____ gases.
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Match the following products with their corresponding reactions:
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Which solid is produced from the thermal decomposition of calcium carbonate?
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The emission of brown fumes occurs when heating lead nitrate.
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What is calcium oxide commonly known as?
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What type of energy causes the decomposition of AgCl and AgBr in sunlight?
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The decomposition reactions described are endothermic reactions.
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Write the reaction of barium hydroxide with ammonium chloride.
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The gas produced in the reaction of silver bromide is ______.
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In the activity with copper sulfate solution, what happens to the iron nails?
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The gas produced during the decomposition of silver chloride is Cl2.
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Name the substance 'X' used for white washing.
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Match the following substances with their corresponding products:
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What type of reaction is characterized by the release of heat?
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Respiration is an endothermic process.
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What is released during an exothermic reaction?
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The reaction of glucose with oxygen produces carbon dioxide, water, and __________.
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Match the chemical reaction with its description:
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Which of the following is NOT an example of an exothermic reaction?
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What happens to ferrous sulphate crystals when heated?
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Exothermic reactions can occur without a change in substance.
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Which of the following is an example of a decomposition reaction?
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Respiration is considered an endothermic reaction.
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Define a precipitation reaction and provide an example.
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In the reaction of magnesium with hydrochloric acid, the products formed are magnesium ________ and ________.
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Match the following terms with their definitions:
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What is the outcome of the reaction between copper metal and silver nitrate?
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Endothermic reactions absorb energy from their surroundings.
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List one reason why iron articles are painted.
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Study Notes
Observations of Chemical Reactions
- Observing temperature changes in conical flasks or test tubes can indicate a chemical reaction.
- Key signs of a chemical reaction include:
- Change in state (solid, liquid, gas)
- Change in color
- Evolution of gas (bubbling, fizzing)
- Change in temperature
Chemical Equations
- Word equations provide a concise way to summarize chemical reactions.
- Example: Magnesium + Oxygen → Magnesium oxide shows reactants and products clearly.
- Reactants are placed on the left side with a plus sign (+), while products are on the right with an arrow indicating the reaction direction.
Types of Reactions
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Exothermic Reactions: Release heat during product formation.
- Example: Burning of natural gas (CH₄ + 2O₂ → CO₂ + 2H₂O).
- Respiration is also exothermic, where glucose (C₆H₁₂O₆) is broken down into carbon dioxide, water, and energy.
- Decomposition of vegetable matter into compost is an exothermic process.
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Decomposition Reactions: Involve a single reactant breaking down into simpler products.
- Example: Heating ferrous sulfate (2FeSO₄) produces ferric oxide (Fe₂O₃), sulfur dioxide (SO₂), and sulfur trioxide (SO₃).
- Thermal decomposition occurs when heat is applied, like calcium carbonate (CaCO₃) breaking down into calcium oxide (CaO) and carbon dioxide (CO₂) upon heating.
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Endothermic Reactions: Absorb energy, usually in the form of heat, light, or electricity.
- Example: Barium hydroxide and ammonium chloride reaction absorbs heat, making the mixture feel cold.
Displacement Reactions
- Involve one element or ion displacing another in a compound.
- Example: Iron nails immersed in copper sulfate solution exhibit displacement reaction where copper is deposited on the iron nails.
Key Concepts in Reactions
- Precipitation Reaction: Formation of an insoluble substance (precipitate) when mixing certain solutions.
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Oxidation and Reduction: Defined in terms of gain or loss of oxygen.
- Oxidation: Gain of oxygen (e.g. Fe to Fe₂O₃).
- Reduction: Loss of oxygen (e.g. CuO to Cu).
Practical Applications
- Painting iron to prevent corrosion by creating a protective barrier.
- Flushing oil and fat-containing food items with nitrogen to prevent rancidity, prolonging shelf life.
Experimental Activity
- Analyze temperature changes when reacting substances like potassium sulfate, ammonium nitrate, anhydrous copper sulfate, and iron fillings in separate beakers to identify which reactions are exothermic or endothermic.
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Description
This quiz covers the fundamental aspects of chemical reactions, including the observations that indicate a reaction, the structure of chemical equations, and the various types of reactions such as exothermic processes. Learn about temperature changes, state changes, and how to represent reactants and products effectively.