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Calor-imetry (heat/energy) – (measuring) This is all about keeping track of where the energy goes! Physical changes are often accompanied by a transfer.

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Presentation on theme: "Calor-imetry (heat/energy) – (measuring) This is all about keeping track of where the energy goes! Physical changes are often accompanied by a transfer."— Presentation transcript:

1 Calor-imetry (heat/energy) – (measuring) This is all about keeping track of where the energy goes! Physical changes are often accompanied by a transfer of energy. To understand that transfer of energy, you must consider both the substance in question and its surroundings.

2 Calorimetry Energy transfers that result in a temperature change for the substance and its surroundings. – Examples: 1. external heat source 2. substance loses heat to the surroundings 3. substance gains heat from the surroundings 4. whole system loses heat energy

3 Energy transfers that result in a temperature change for the substance and its surroundings system Surroundings 1 2 3 4 substance

4 Energy transfers that result in a temperature change for the surroundings (but not the substance) Example: – Ice melting… What has to happen to the ice for it to melt? Where would that energy have come from? Does the temperature of the ice change as it becomes liquid water? What about the temperature of the air around the ice cube?

5 Calorimetry Energy changes in a laboratory setting are measured using a calorimeter. If heat is produced during the change, then the process/change/reaction is exothermic and the temperature of the surroundings will increase. Examples:1. hand warmer2. flame

6 Calorimetry If heat is consumed during the change, then the process/change/reaction is endothermic and the temperature of the surroundings will decrease. Examples:1. cold pack2. ice melting

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8 Review! 1. The units in which heat energy is expressed are either or. 2. The quantity of heat energy required to raise the temperature of a unit mass of a substance by 1  C is called the of the substance. 3. The value of this quantity for water is.

9 4. In the calorimeter shown in the figure, a sample of solute releases 2.00 x 10 3 cal as it dissolves in water. Is this physical change endothermic or exothermic? 5. If the thermometer in the calorimeter shows a decrease in temperature over the course of an experiment, is the physical change in the chamber endothermic or exothermic?


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