Energy Changes in Systems

In this lesson, we will be covering energy changes in systems. The main objective of this lesson is to understand changes in thermal energy.

Key Concepts:

• Converting a change in temperature into a change in thermal energy.
• Factors affecting thermal energy: temperature, mass of the material, and type of material.
• The structure of different materials affects the amount of thermal energy at the same temperature.
• The formula for calculating the change in energy is ΔE = mcΔθ.

Important Units:

• ΔE: Energy change (unit: Joules)
• m: Mass of the material (unit: kilograms)
• c: Specific heat capacity of the material (unit: joules per kilogram degrees Celsius)
• Δθ: Change in temperature (unit: degrees Celsius)

Notes:

• Delta (Δ) is a symbol used to indicate a change in a quantity.
• Sometimes delta E is represented as Q, depending on the board.
• Specific heat capacity (c) may be given in different units, such as kilojoules or grams.
• Be careful with units and ensure consistency when calculating energy and mass.
• It is important to consider if there is any heat loss to the surroundings in real-world scenarios.

Example Calculation: In a specific scenario, a beaker of 200 grams of water is heated from 20°C to 40°C using a Bunsen burner. The specific heat capacity of water is 4.2 kilojoules per kilogram degrees Celsius. The change in energy can be calculated as follows:

• Mass (M): 0.2 kg
• Δθ: 20°C
• ΔE = mc Δθ = 0.2 kg x 4.2 kJ/kg°C x 20°C = 16.8 kilojoules or 16,800 Joules.

By understanding the formula and concepts explained in this lesson, you should now be able to calculate changes in thermal energy and apply the equation to solve similar problems. Remember to check units and consider factors like heat loss to the surroundings.