Chemistry (9) 🧪⚛️🎀

• What are finite resources?

  Resources that cannot be replaced
• Why do estimates of finite resources differ?

  Due to uncertainties in future use and discovery
• What is sustainability in resource use?

  Meeting current needs without harming future generations
• What percentage of Earth's water is not potable?

  97%
• What is potable water?

  Water that is safe for drinking
• What is the main use of potable water?

  For drinking and agriculture
• How does rainwater contribute to fresh water supplies?

  It replenishes lakes and aquifers
• What impurities are found in natural water sources?

  Dissolved minerals and microorganisms
• What is the purpose of treating drinking water?

  To reduce impurities to safe levels
• What is one method used to sterilize water?

  Adding chlorine
• What is desalination?

  Converting salty water into potable water
• Why is distillation expensive?

  It requires large amounts of energy
• What is reverse osmosis?

  A method using membranes to purify water
• What is the main disadvantage of reverse osmosis?

  Corrosion of pumps by salty water
• What is the first step in sewage treatment?

  Screening to remove large solids
• What happens during primary treatment of sewage?

  Solid sediments settle out from the mixture
• What is the role of bacteria in secondary treatment?

  They break down organic matter aerobically
• What is produced from the anaerobic digestion of sewage sludge?

  Methane gas
• What can biogas be used for?

  To power the sewage treatment plant
• What is the purpose of drying sewage sludge?

  To reduce its volume for transport
• What does an LCA assess?

  The environmental impact of products
• What stages are included in an LCA?

  Raw material extraction to disposal
• Why are LCAs sometimes subjective?

  They require subjective judgments on impacts
• What is a benefit of recycling aluminum?

  90% energy saving
• What is the main advantage of recycling iron and steel?

  It conserves resources and energy