Untitled Quiz

Specific Heat

• A calorimeter is a lightweight insulated flask containing water, used to measure the specific heat of objects
• How it works: An object is placed in a calorimeter, allowing it to reach thermal equilibrium with the water. By analyzing the temperature changes of both the object and the water, you can calculate the specific heat of the object.
• Key Principle: Energy is conserved. This allows us to calculate the specific heat of the object in the calorimeter.
• Coffee-cup Calorimeter: A common type of calorimeter used under constant atmospheric pressure.

Heat Transfer in Calorimetry

• Energy Conservation: The energy absorbed inside the calorimeter must be equal to the energy released inside it, i.e., q_absorbed = - q_released.
• Equation for Heat Transfer: q = m x C x ΔT where:
  • q is the heat energy transferred
  • m is the mass of the substance
  • C is the specific heat of the substance
  • ΔT is the change in temperature

Specific Heat Examples

• Example 1: A 75.0g piece of lead (specific heat = 0.130 J/g°C) initially at 435°C is placed in 125.0g of water at 23.0°C.
  • The final temperature of the mixture will be 30.5°C.
• Example 2: A 97.0g sample of gold at 785°C is dropped into 323g of water at 15.0°C. Gold has a specific heat of 0.129 J/g°C.
  • The final temperature of the mixture will be 22.1°C.

Homework Examples

• HW #2: 59.0g of water at 13.0°C is mixed with 87.0g of water at 72.0°C
  • The final temperature of the system will be 48.2°C.
• HW #4: 240g of water initially at 20.0°C is mixed with an unknown mass of iron at 500.0°C (C_Fe = 0.4495 J/g°C). The final temperature is 42.0°C.
  • The mass of the iron is 107g.

Cold Therapy

• Benefits:
  • Decreases inflammation: Cold constricts blood vessels, reducing blood flow and inflammation.
  • Slows joint fluid production: Excessive synovial fluid can contribute to swelling and discomfort.
  • Distracts the brain from inflammation: Cold stimulates sensory receptors in the skin, decreasing pain signals to the brain.
• Application: Cold packs should be applied for no more than 20 minutes at a time, but can be repeated throughout the day.

Heat Therapy

• Primary Effects:
  • Increased metabolism leading to blood vessel relaxation (vasodilation).
  • Increased blood supply to cool down the heated area.
• Methods:
  • Conductive: Direct application of heat through hot towels, heating pads.
  • Radiation: Infrared lamps.
  • Radio wave heating (Diathermy): Produces deep heating directly in tissues.
  • Ultrasonic heating: Uses high-frequency sound waves to heat the tissue.

Ultrasonic Heating

• Mechanism: Unlike electromagnetic waves, ultrasonic waves cause mechanical vibration in tissues, increasing kinetic energy and leading to heating.

Energy Expenditure: Fat Loss

• Physical Activity:
  • Example: A person wishing to lose 4.54kg of fat through physical activity will need to work at 15kcal/min for 2810 minutes (47 hours), assuming a maximum energy expenditure of 9.3kcal/g of fat.
• Dieting:
  • Example: To lose 4.54kg of fat by reducing food intake, a person consuming 2500kcal/day will need to diet for 84.4 days.

Basal Metabolic Rate (BMR)

• Determination: BMR is determined by measuring oxygen consumption at rest.
• Use: Can be used to determine the energy expenditure of various organs and estimate food energy used during physical activities.
• Measurement: Oxygen consumption, carbon dioxide production, and heat production can be measured to assess BMR.

Body Mass Index (BMI)

• Definition: BMI is a measure of body fat based on height and weight.
• Significance: BMI does not diagnose health conditions but can indicate an individual's risk level for certain health problems.
• Range: BMI values span from underweight to obese.