Chemical Reactions and Environmental Impact
What is the Difference Between a Chemical and a Physical Transformation?
In a chemical transformation, substances disappear, and new ones appear. These are called chemical reactions.
In a physical transformation, we have the same substances at the beginning and the end of the process.
What is a Chemical Reaction?
A chemical reaction is a process by which some substances, called reactants, become new substances, called products.
How are Chemical Reactions Represented?
Chemical reactions are represented with chemical equations.
For example:
CH4(g) + 2O2(g) CO2(g) + 2H2O(g)
- Red: Chemical formulas of the substances
- Green: State of the substance
- Black: Coefficients indicate the proportion of the number of molecules
Conservation of Mass in Chemical Reactions
In a chemical reaction, no atom disappears or appears, so the mass of the reactants is equal to the mass of the products.
- Some of the atoms that form the reactants must break. That requires an amount of energy.
- When they join again to form the product, they release another amount of energy. This energy is different from the previous energy.
- The recombination of atoms in a chemical reaction means that the initial bonds break, and new bonds form.
Energy Changes in Chemical Reactions
The comparison of the energy needed to break the bonds of the reactants and the energy released to form the products (energy balance) shows two situations:
Exothermic Processes
Energy needed to separate the atoms is lower than the energy released when they join again.
Endothermic Processes
Energy needed to separate the atoms is greater than the energy released when they join again.
Factors Affecting the Rate of a Chemical Reaction
Temperature
The higher the temperature of a process, the faster the speed at which it occurs because the particles move faster and interact more.
Concentration
The higher the concentration of a reactant, the higher the reaction rate because there is a larger quantity of particles available to react, and they are close together.
Acids and Bases
What are Acids and Bases?
Acids and bases are substances that react with each other according to the following reaction:
Acid + Base Salt + Water
Characteristics of Acids
- Acids are substances that have a sour taste.
- Acids react with limestones such as marble.
Characteristics of Bases
- Bases are substances that have a bitter taste and soapy feel.
- Bases do not usually attack metals.
Environmental Issues
Acid Rain
Origin
The fuels used for locomotion and electricity generation emit sulfur and nitrogen oxides. These chemicals react with water in the clouds and produce acids.
Consequences
- The soil and the water of lakes and rivers acidify.
- Trees and aquatic organisms become ill and can die.
- The acid attacks and dissolves limestone (basic).
Solution
- Decrease the consumption of fossil fuels.
- Eliminate the sulfur before using the fuel.
- Eliminate oxides before releasing them into the atmosphere.
Greenhouse Effect
Origin
- The problem appears when the presence of carbon dioxide, methane, and water vapor in the atmosphere is larger than normal.
- The abuse of fossil fuels is the source of the carbon dioxide.
- The emission of livestock digestion (farts) and escapes from underwater methane pockets are the main sources of methane.
Effect
An increase in the average temperature of the Earth.
Consequences
- Melting of polar ice caps and glaciers, increase in the sea level, and modification of ocean currents.
- Climate change with an increase in drought and violent atmospheric phenomena.
- Increase of wildfire risk.
- Extinction of species due to the destruction of their habitats.
Solution
- Reduce the use of fossil fuels by promoting renewable energy sources.
- Control the amount of livestock used for food by responsible consumption.
Ozone Layer Depletion
Origin
CFCs are man-made gases used for several things. When CFCs come in contact with UV rays at the higher layers of the atmosphere, they react with the ozone molecules, breaking them.
Effect
The ozone layer absorbs the main part of the UV radiation. As a result of the hole in the ozone layer, the amount of UV radiation reaching Earth’s surface is higher.
Consequences
- Skin burn
- Blindness
- Skin cancer
- Lethal mutations
Solution
To reduce the emission of CFCs.
Waste and Pollution
| Type of Waste | Effect | Solution |
|---|---|---|
| Plastics that never decompose, oil spills | Traps to marine animals, animals, and plants die by contact or by asphyxiation | Reduce consumption and recycle the material used, improve fuel collection methods and use alternative energies |
| Mining waste, toxic products in ponds | Kill all living things | Nature cannot eliminate these substances, so the only solution is to minimize the extraction of minerals |
| Groundwater contamination | Contamination of potable water | Improve information for farmers |
| Eutrophication of water | Make the water uninhabitable | Stop the uncontrolled dumping of wastewater |
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