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UNIT 7: THERMOCHEMISTRY Scientist: ____________________ Per: _________ Date: _________ #3 SPECIFIC HEAT CAPACITY Calculating Heat Transfer: Q = (m)(c)(ΔT) [Quesadillas= meat x cheese x tortillas] Heat represents the TOTAL energy. To calculate it, we need both temperature and mass. In addition, we also need a third variable – specific heat capacity – to represent the thermal properties of the specific material that is being heated. Use this formula to determine the amount of energy required in a temperature change Q = m∙c∙ΔT where Q Heat energy in joules (J). m the mass in grams (g). ΔT the temperature change (ΔT = Tfinal – Tinitial) in degrees Celcius (oC). c the specific heat capacity – a unique value which depends on the material that is being heated. The unit for specific heat capacity is Joules per gram per degree Celcius (J/g·oC) Specific Heat Capacity (in J/g oC) Water 4.2 Silver 0.2 Magnesium 1.0 Tin 0.3 Mercury 0.1 Zinc 0.4 Aluminum Lithium Tin Titanium Silver Neon 0.9 3.6 0.3 0.5 0.2 1.0 Example: How much energy is required to heat 100 grams of water from 20oC to 100oC. The specific heat capacity of water is 4.2 J/g·oC 1. How much heat is absorbed when 15g Neon is heated from 10 °C to 20 °C? 2. How much heat is released when 10g Aluminum is cooled from 20 °C to 5 °C? 3. How much heat is lost when 12g Zinc changes from 16 °C to 12 °C? 4. How much energy is needed to increase 15g Silver to 10 °C from 18 °C? 5. How much energy is lost when 8g liquid water cools from 4 °C to 2 °C? 6. How much heat energy is required to raise the temperature of 5 kg of tin from 10 oC to 20 oC? 7. 5000 J of energy is added to 25 grams of water. How much will the temperature increase? 8. 2000 J of energy is added to a sample of lithium at room temperature (25 oC). After the heat is added, the temperature is measured again, this time reading 50 oC. What is the mass of the lithium sample? 9. 800 J of energy is added to a 15 g sample of silver at 10 oC. What is the temperature of the silver after it has been heated? 10. 3000 joules of energy is added to 100 grams of an unknown substance. Using a thermometer, you carefully observe the beginning and end temperatures and note that the temperature increases by 60oC. What is the specific heat capacity? What substance is it?