Heat and Energy — Important Questions

Solar energy, Wind energy, Hydroelectric energy

Solar energy, wind energy, and hydroelectric energy are renewable sources as they can be replenished naturally. Coal and natural gas are fossil fuels that are non-renewable as they take millions of years to form.

Carbon dioxide, Methane, Water vapour

Carbon dioxide, methane, and water vapour are greenhouse gases that trap heat in the atmosphere. Nitrogen and oxygen are major atmospheric gases but are not greenhouse gases.

Linear

Energy flow in an ecosystem is linear - it moves in one direction from producers to consumers and finally becomes unusable heat. It does not cycle back like matter.

It expands

Water shows anomalous expansion - it expands when cooled from 4°C to 0°C instead of contracting. This is unusual behavior as most substances contract on cooling.