A balloon is cooled by removing 0.784 kJ of heat. It shrinks on cooling, and the atmosphere does 655 J of work on the balloon. Calculate the change in internal energy, ∆E, of the system.

The correct answer is -0.129 kJ

Explanation:

In the given case, the cooling of the balloon is done by withdrawing 0.784 J of heat, and the work done by the atmosphere on the balloon is 655 J. First, there is a need to transform kJ into J, 1 kJ = 1000 J. So, 0.784 kJ would be 784 J.  

The ΔE or the change in the internal energy can be calculated by using the formula, ΔE = q + w (1).  

In the given case, q refers to the heat moved out of the system, that is, the value of q would be less than 0 or will be a negative quantity. Therefore, the heat moved out of the system will be -784 J. On the other hand, as the work or w is done on the system, therefore, the value of w would be more than 0 or will be a positive quantity. Thus, the value of w will be +655 J.  

Now putting the values in the equation (1) we get,  

ΔE = -784 J + 655 J

ΔE = -129 J or -0.129 kJ

As the change in internal energy comes out to be a negative value, therefore, the process is considered exothermic.  

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.

1. they vary with a higher number because boiling is way hotter than melting