Chapter 3

• Because water is the substance that makes life possible on Earth, astronomers hope to find evidence of water on newly discovered planets orbiting distant stars.
• Life on Earth began in water and evolved there for 3 billion years before colonizing the land.
• Even terrestrial organisms are tied to water.
  • Most cells are surrounded by water.
  • Cells are about 70–95% water.
  • Water is a reactant in many of the chemical reactions of life.
• Water is the only common substance that exists in the natural world in all three physical states of matter: solid ice, liquid water, and water vapor.

A small birthday candle is weighed, then lighted and placed beneath a metal can containing 100 mL of water. Careful records are kept as the temperature of the water rises. Data from this experiment are shown on the graph. What amount of heat energy is released in the burning of candle wax?

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A) 0.5 kilocalories per gram of wax burned - Correct Answer

B) 5 kilocalories per gram of wax burned

C) 10 kilocalories per gram of wax burned

D) 20 kilocalories per gram of wax burned

E) 50 kilocalories per gram of wax burne

Carbon dioxide (CO₂) is readily soluble in water, according to the equation CO₂ + H₂O ↔ H₂CO₃. Carbonic acid (H₂CO₃) is a weak acid. If CO₂ is bubbled into a beaker containing pure, freshly distilled water, which of the following graphs correctly describes the results