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Questions and Answers
What happens to a substance that gains oxygen during a reaction?
During the reaction CuO + H2 → Cu + H2O, what happens to copper(II) oxide?
In the reaction ZnO + C → Zn + CO, what is the role of carbon (C)?
What happens to a substance that loses hydrogen during a reaction?
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In the reaction MnO2 + 4HCl → MnCl2 + 2H2O + Cl2, what happens to MnO2?
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Is magnesium being oxidised or reduced when it burns in air and changes into magnesium oxide?
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If a substance gains hydrogen during a reaction, what result does it lead to?
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What does the reddish brown powder on iron articles signify?
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What term is commonly used to describe the process of iron articles getting coated with a reddish brown powder over time?
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What type of reaction occurs when milk is left at room temperature during summers?
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Which type of reaction takes place when an iron tawa/pan/nail is exposed to humid atmosphere?
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What type of reaction occurs when food gets digested in our body?
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In the reaction MnO2 + 4HCl → MnCl2 + 2H2O + Cl2, what type of reaction is occurring?
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What type of reaction happens when grapes get fermented?
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When we respire, what type of chemical process is involved?
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What happens when magnesium ribbon burns in air?
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During the burning of magnesium ribbon, what is the ash formed known as?
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Which type of change occurs when food is cooked?
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What type of reaction takes place when an iron tawa/pan/nail is exposed to humid atmosphere?
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Study Notes
Oxidation and Reduction Reactions
- A substance gains oxygen during a reaction, it is said to be oxidised.
- A substance loses oxygen during a reaction, it is said to be reduced.
- Example: CuO + H2 → Cu + H2O, where CuO is reduced and H2 is oxidised.
Examples of Redox Reactions
- 2ZnO + C → 2Zn + CO, where C is oxidised and ZnO is reduced.
- MnO2 + 4HCl → MnCl2 + 2H2O + Cl2, where HCl is oxidised and MnO2 is reduced.
Corrosion
- Corrosion occurs when a metal is attacked by substances around it, such as moisture, acids, etc.
- Examples: rusting of iron, tarnishing of copper and silver.
- Corrosion causes damage to car bodies, bridges, iron railings, ships, and other metal objects.
Rancidity
- Rancidity occurs when fats and oils are oxidised, changing their smell and taste.
- Substances that prevent oxidation (antioxidants) are added to foods containing fats and oil to prevent rancidity.
- Keeping food in air-tight containers helps to slow down oxidation.
Types of Chemical Reactions
- Combination reaction: a single product is formed from two or more reactants.
- Example: CaO + H2O → Ca(OH)2, where calcium oxide reacts with water to form slaked lime.
Exothermic and Endothermic Reactions
- Exothermic reaction: a reaction that releases heat, increasing the temperature of the surroundings.
- Endothermic reaction: a reaction that absorbs heat, decreasing the temperature of the surroundings.
- Example of exothermic reaction: CaO + H2O → Ca(OH)2, where heat is released.
Displacement and Double Displacement Reactions
- Displacement reaction: a reaction in which one element displaces another from a compound.
- Double displacement reaction: a reaction in which two compounds exchange partners.
- Example of displacement reaction: Zn + CuSO4 → ZnSO4 + Cu, where zinc displaces copper.
- Example of double displacement reaction: NaCl + AgNO3 → NaNO3 + AgCl, where sodium chloride reacts with silver nitrate.
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Description
Test your knowledge on the process of corrosion affecting metals like copper and silver. Learn about the black and green coatings formed on these metals, and the damage caused by corrosion to various objects such as car bodies, bridges, and ships.
