Question

Performance For one day, record situations that show evidence of oxidation- reduction reactions. Identify the reactants and the products, and determine whether there is proof that a chemical reaction has taken place.

Short answer

Observe, record, and analyze different oxidation-reduction reactions in daily life, identifying reactants and products, and confirming the occurrence of chemical reactions through various indicators.

Step-by-step solution

Identify Situations

Begin by observing various environments such as the kitchen, laboratory, or outdoors for any signs of oxidation-reduction reactions. Examples include rusting of iron, a burning candle, or fruit turning brown.

Record Observations

Document each situation where an oxidation-reduction reaction is suspected. Include details such as the time, location, and a brief description of what is observed.

Identify Reactants and Products

For each observed situation, identify the reactants (substances before the reaction) and the products (substances after the reaction). For instance, in rusting metal, iron and oxygen are reactants, and rust (iron oxide) is the product.

Determine Evidence of Chemical Reaction

Evaluate whether there is proof of a chemical reaction. Indicators include color change, temperature change, gas production, or formation of a precipitate. If these are present, it confirms a chemical reaction.

Analyze Results

Analyze the collected data to understand which situations are genuine oxidation-reduction reactions by verifying if electrons were transferred between reactants.

Key concepts

Reactants and Products

In a chemical reaction, the substances you start with are called reactants, and the substances you get at the end are called products. Identifying reactants and products is essential to understand what exactly changes during the reaction.
To identify the reactants, think about what materials you have before any change occurs. For example, when iron rusts, your reactants are iron (Fe) and oxygen (O₂).
To identify the products, look at what new materials are formed after the reaction. Using the same rust example, the product is iron oxide (Fe₂O₃), commonly known as rust.
Knowing your reactants and products helps you write the chemical equation for the reaction, showing what goes in and what comes out.
For example:

• Reactants: Fe + O₂
• Products: Fe₂O₃

Chemical Reaction Indicators

How can you tell if a chemical reaction has taken place? There are several key indicators to look for:

• Color change: If the substance changes color, it's a good clue a reaction has occurred. For instance, a banana turning brown indicates an oxidation-reduction reaction.
• Temperature change: If the reaction makes the surroundings warmer or cooler, it's a sign of a chemical process. For example, combustion reactions release heat.
• Gas production: If you see bubbles or smell gas, it usually means a new substance is being formed. For instance, burning a candle produces carbon dioxide gas.
• Formation of a precipitate: When a solid forms in a liquid solution, it's known as a precipitate. This can be another sign of a chemical reaction.

Observing these indicators helps you confirm whether a chemical reaction, such as an oxidation-reduction reaction, is actually happening.

Electron Transfer

Oxidation-reduction (redox) reactions involve the transfer of electrons between substances. It's how substances change their oxidation state.
In any redox reaction, one reactant loses electrons, and another gains them. The substance that loses electrons is said to be oxidized, while the substance that gains electrons is reduced.
The substance that loses electrons (gets oxidized) is called the reducing agent, and the substance that gains electrons (gets reduced) is called the oxidizing agent.
For example, when iron rusts, iron (Fe) loses electrons and becomes Fe³⁺ (oxidized), while oxygen (O₂) gains those electrons to form O^2- (reduced).
The overall reaction involves:

• Oxidation: Fe → Fe³⁺ + 3e^-
• Reduction: O₂ + 4e^- → 2O^2-

The main thing to remember is that electrons are moving from one substance to another in these reactions, driving the transformation from reactants to products.