1. Answer;
- Exothermic reaction
Explanation;
-Exothermic reactions are types of chemical reactions in which heat energy is released to the surroundings. Since enthalpy change is the difference between the energy of products an that of reactants. It means that in an exothermic reaction the energy of products is less than that of products. In this case an energy of 315kJ is released to the surroundings.
2. Answer;
Conserved
-The total amount of energy before and after a chemical reaction is the same. Thus, energy is conserved.
Explanation;
-According to the law of conservation of energy, energy is neither created nor destroyed. Energy may change form during a chemical reaction. For example, energy may change form from chemical energy to heat energy when gas burns in a furnace. However, the exact amount of energy remains after the reaction as before, which is true for all chemical reactions.
Explanation:
1. Boyle's Law states that pressure is inversely proportional to the volume of the gas at constant temperature and number of moles.
(At constant temperature and number of moles)

2. Charles' Law states that volume is directly proportional to the temperature of the gas at constant pressure and number of moles.
(At constant pressure and number of moles

3. Gay Lussac's Law states that tempertaure is directly proportional to the pressure of the gas at constant volume and number of moles of gas
(At constant volume and number of moles)

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The correct answer is C) A substance changes color when heated, but changes back when cooled. Hope this helps.