University:
Carleton University
Course:
CHEM 1001 | General Chemistry I
Academic year:

2024
Views:

160

Pages:

2
Author:

ali

Conservation of energy - energy can be converted but cannot be created or destroyed. Heat capacity Heating causes changes in temperature (1) Different substances heated with the same amount of energy do not give the same temperature change - ΔT. Heat capacity (C) quantifies the energy changes - heat needed to raise temp by 1 K Specific heat capacity (Cs) refers to 1g of substance. Water has high Cs - needs lots of energy to increase T Metals have lower Cs - need less energy to increase T If we apply some amount of heat (q) to metal and water with some mass and same initial T, then metal will be hotter. Generally, if quantity of energy (heat, q) is transferred to a mass (m, grams) of a substance, and the temperature rises by ΔT, Specific heat capacity = quantity of energy / (mass x temperature rise) Cs = q / (m x ΔT) units: J/g/K rearrange to give q = Cs x m x ΔT Δ = delta means change in (Tfinal - Tinitial) Heat transferred away from system (released) Tfinal lower than Tinitial ΔT is negative q is negative exothermic Heat transferred to system (absorbed) Tfinal higher than Tinitial ΔT is positive q is positive endothermic Cs is assumed to be always positive Lecture C energy and changes of state Solids melting: atoms/molecules/ions move around breaking attractive forces holding them rigid Liquid boiling: atoms/molecules move apart attractive forces are minimal