Combustion, Oxidation & Conservation of Mass

• Combustion releases energy when hydrocarbons burn with plenty of oxygen, producing carbon dioxide and water.
• Hydrocarbons contain only carbon and hydrogen and are the main component of many fuels.
• Combustion is an exothermic reaction, transferring energy to the surroundings as heat.
• The word equation for hydrocarbon combustion is: hydrocarbon + oxygen → water + carbon dioxide.
• Combustion is an oxidation reaction where substances react with oxygen.
• Metals can also be oxidized, forming metal oxides: metal + oxygen → metal oxide.

Tests

• Carbon dioxide turns limewater milky.
• Hydrogen burns with a squeaky pop.
• Water turns blue cobalt chloride pink and anhydrous copper sulfate blue.
• Hydrated copper sulfate loses water upon heating, forming anhydrous copper sulfate.

Conservation of Mass

• In chemical reactions, the total mass of reactants equals the total mass of products.
• Metals heated in air appear to gain mass due to the addition of oxygen.
• Burning hydrocarbon fuels appear to lose mass as carbon dioxide and water vapor escape into the air.

Phlogiston Theory

• Before oxygen's discovery, combustion was explained by the release of phlogiston into the air.
• The phlogiston theory failed to explain why metals gain mass when reacting with air.

Fire Triangle

• The fire triangle includes heat, fuel, and oxygen. Removing any of these extinguishes the fire.
• Water extinguishers remove heat.
• Powder and carbon dioxide extinguishers exclude oxygen.
• Foam extinguishers remove heat and exclude oxygen.
• Oil fires should not be treated with water, as it can cause the oil to spit and spread the fire.

Hazard Symbols

• Hazard symbols indicate necessary precautions when handling substances.

Air Pollution

• Complete combustion produces carbon dioxide and water: hydrocarbon + oxygen → carbon dioxide + water.
• Incomplete combustion produces carbon dioxide, water, carbon monoxide, and soot: hydrocarbon + oxygen → carbon dioxide + water + carbon monoxide + carbon
• Impurities like sulfur react with oxygen to form sulfur dioxide: sulfur + oxygen → sulfur dioxide.
• High temperatures in engines cause nitrogen and oxygen to react, forming nitrogen oxides: nitrogen + oxygen → nitrogen oxides.
• Many products from burning fossil fuels are pollutants, harming habitats and organisms.

Acid Rain

• Acid rain results from sulfur dioxide and nitrogen oxides dissolving in rainwater.
• Neutralization processes and catalytic converters reduce these gases from power station chimneys and vehicle exhausts.
• Catalytic converters also remove carbon monoxide.

Greenhouse Effect and Global Warming

• Greenhouse gases trap heat in the Earth's atmosphere, causing the greenhouse effect.
• Increased carbon dioxide from burning fossil fuels is linked to global warming.
• Global warming is predicted to cause climate change.
• Reducing carbon dioxide emissions is the best way to control global warming.

Explore combustion as an exothermic oxidation reaction involving hydrocarbons and metals. Learn to identify reaction products like carbon dioxide and water using specific tests. Understand the principle of conservation of mass, including apparent mass changes in reactions.