AP Chemistry Question of the Day --4

Here comes the answer to question 3 I posted yesterday. The correct answer is B. 

First Law of Thermodynamics states that the total quantity of energy in the universe is assumed to remain constant. Energy can not be destroyed or generated, it can only be converted from one form to the other. Chemical systems undergo three main processes that change their energy: heating/cooling, phase transitions, and chemical reactions. In Question 3, the container is insulated, so it is considered a closed system. Therefore, there is no energy exchange with the surroundings. The energy the metal lost should be equal to the energy the water gained. The temperature changes of the metal and water are different because they have different heat capacities. Specific heat (c) is defined as the amount of heat required to raise the temperature of 1g of a substance by 1 degree in temperature.

Here q is the heat amount, m is the mass of the substance and Delta T is the temperature change. Since the heat the water gained is the same amount as the metal lost and both the metal and the water has a mass of 100g. We can conclude that since the metal temperature changed more than the water temperature, the metal has a smaller specific heat than water.

This is also the key behind Calorimetry. Always remember  Energy can not be destroyed or generated, it can only be converted from one form to the other.

Following is Question 4 of the series:

4.Which of the following particulate diagrams best shows the formation of water vapor from hydrogen gas and oxygen gas in a rigid container at 125C?

I will post the answer and explanation tomorrow.

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