12th grade science

Example

Producers in a field store 50000 kJ/m² of energy per year. Primary consumers gain 2500 kJ/m². What is the efficiency of energy transfer, in %?

1. 2500 ÷ 50000 × 100 = 5
2. So the answer is: 5 %

Answer: 5 %

Example

A gas at 200 kPa occupies 24 cm³. At constant temperature it is compressed to 12 cm³. What is its new pressure, in kPa?

1. p₂ = 200 × 24 ÷ 12 = 400
2. So the answer is: 400 kPa

Answer: 400 kPa

Example

A ray of light enters a material from air with an angle of incidence of 60°. The angle of refraction is 33°. What is the refractive index of the material? (n = sin i ÷ sin r; give 2 decimal places)

1. sin 60° = 0.866, sin 33° = 0.5446
2. 0.866 ÷ 0.5446 = 1.59
3. So the answer is: 1.59

Answer: 1.59

Example

Is this a positive or negative climate feedback: more CO₂ boosts plant growth, which takes up some CO₂?

1. A negative feedback works against the initial change.
2. So the answer is: negative feedback (reduces warming)

Answer: negative feedback (reduces warming)