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Energy Notes

Energy Definitions

  • Energy: The ability to do work. Living things require energy from food to perform life processes, such as movement, respiration, and growth.

Sources of Energy

  • Main Source: The sun is the primary source of energy. All life forms depend directly or indirectly on solar energy.

  • Plants:

    • Photosynthesis: Plants convert sunlight into food directly through photosynthesis, utilizing carbon dioxide and water to produce glucose and releasing oxygen.

    • Storage: Excess food produced (sugar) is stored as starch in various plant parts (leaves, stems, roots, fruits).

  • Animals:

    • Cannot produce their own food as they lack chlorophyll. They depend indirectly on the sun by feeding on plants or other animals.

    • Energy consumption can always be traced back to the sun.

Testing for Starch

  • Use iodine solution to test for starch on plant surfaces:

    • Brown Iodine: Indicates no starch present.

    • Dark Blue/Yellowish Brown Iodine: Indicates starch presence.

Rate of Photosynthesis

  • Definition: Speed at which plants produce food under light.

  • Factors Affecting Rate:

    • Intensity of Light: More light leads to a faster rate.

    • Amount of Carbon Dioxide: Higher carbon dioxide leads to a faster rate.

    • Amount of Chlorophyll: More chlorophyll means a faster rate.

Types of Energy

  • Kinetic Energy: Energy of moving objects. More speed or mass equates to more kinetic energy.

  • Potential Energy: Stored energy with several types:

    • Chemical Potential Energy: Stored in food, fuel, batteries.

    • Elastic Potential Energy: Energy stored in stretched or compressed objects. Returns to kinetic energy upon release.

    • Gravitational Potential Energy: Energy based on an object's height above ground. More height implies more gravitational potential energy.

Specific Energy Types

  • Heat Energy: Increases temperature, making objects warm. Essential for maintaining life (e.g., drying clothes, sustaining warmth).

  • Sound Energy: Produced by vibrating objects, travels to our ears, does not travel in a vacuum.

  • Light Energy: Illuminates objects allowing visibility; crucial for photosynthesis in plants.

  • Electrical Energy: Portable energy carried by wires; transmutable into light, heat, or sound.

Energy Conversion

  • Energy transformation examples:

    • Television: Electrical energy → Sound energy + Light energy

    • Flashlight: Chemical energy → Light energy

    • Cycling: Chemical potential energy → Kinetic energy

Energy Conversion Example

  • A ball released from a height loses gravitational potential energy, converting it to kinetic energy upon descent.

Recap Questions

  1. What is energy?

    • The ability to do work.

  2. What is the main energy source for life?

    • The sun.

  3. Factors affecting the rate of photosynthesis?

    • Light intensity, carbon dioxide amount, chlorophyll amount.

  4. Types of energy?

    • Heat, light, sound, electrical, kinetic, potential.

  5. Which has more gravitational potential energy, an 80kg or a 50kg object at a height?

    • The 80kg object has more GPE.