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All 15 Flashcards — Laws of thermodynamics
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Question
State the first law of thermodynamics.
Answer
Energy cannot be created or destroyed; it can only be transformed from one form to another.
💡 Hint
Transformed
Question
State whether energy cycles in ecosystems.
Answer
Energy does not cycle; it flows through ecosystems and is lost as heat.
💡 Hint
Flows, not cycles
Question
Define an open system.
Answer
An open system exchanges both energy and matter with its surroundings.
💡 Hint
Energy + matter exchange
Question
State the main input and the main output of energy in ecosystems.
Answer
Main input is sunlight; main output is heat.
💡 Hint
Sun in, heat out
Question
State the second law of thermodynamics.
Answer
Every energy transfer is inefficient; some energy is dissipated as heat, so less usable energy remains.
💡 Hint
Inefficient + heat
Question
State the first law of thermodynamics.
Answer
Energy cannot be created or destroyed, only transformed.
💡 Hint
Transformed
Question
Explain why less energy is available at higher trophic levels.
Answer
Energy is used for respiration, movement and maintenance and much is lost as heat, so only a small proportion becomes new biomass.
💡 Hint
Respiration + heat
Question
Explain why energy does not cycle in ecosystems.
Answer
Energy flows through ecosystems and is eventually lost as heat, so it cannot be recycled.
💡 Hint
Lost as heat
Question
State the second law of thermodynamics.
Answer
Energy transfers are inefficient and some energy becomes heat.
💡 Hint
Inefficient + heat
Question
State two phrases that commonly gain marks in thermodynamics answers.
Answer
Use “energy is transformed” for the first law and “transfers are inefficient with heat loss” for the second law.
💡 Hint
Exact mark phrases
Question
Define an open system in ecology.
Answer
An open system exchanges energy and matter with its surroundings.
💡 Hint
Energy + matter
Question
Outline the basic pathway of energy through an ecosystem.
Answer
Sunlight is captured by producers, transferred by feeding through consumers, and leaves the system as heat at each step.
💡 Hint
Capture → transfer → heat
Question
Explain why eating at lower trophic levels is often more energy efficient.
Answer
Fewer energy transfers means less heat loss, so more of the original energy supports food production.
💡 Hint
Fewer transfers
Question
Explain how the second law helps explain short food chains.
Answer
Heat loss at each transfer reduces usable energy at higher trophic levels, limiting the number of trophic levels supported.
💡 Hint
Heat loss limits levels
Question
Explain why higher trophic levels contain less energy.
Answer
Energy is lost as heat at each transfer so less usable energy remains to build biomass at higher levels.
💡 Hint
Heat loss
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Full study notes for Laws of thermodynamics
Topic 2.5 hub
Flows of energy and matter
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