Control question

Q1. What is energy? What different kinds of energy can you name?

Answer: Energy is the potential to do some work. If there is work done on a system, this work done is stored as potential energy of the system. If the system in motion, it should have kinetic energy. Sun energy , water enegy, wind energy, energy of fossils an energy from food are the different kinds of energy.

Q2. What can you do with energy?

Answer: Energy is used for change. If things don't have energy, they cannot ever change. That's a very general question though, because everything that has mass has energy (according to Einstein's e = mc²).

Q3. Is kinetic energy an energy source?

Answer: No. kinetic energy is a type of energy. An energy source is like fossil fuels, solar energy, wind, and more.

Q4. What is the relationship between different forms of energy?

Answer: All forms of energy follow law of conservation of energy. The total quantum of energy in this universe will always remain constant. Energy can be transferred from one place to another.

Q5. What is “enthalpy”? Why enthalpy is a extensive quantity?

Answer: Enthalpy refers to the heat energy exchange that occurs during chemical reactions. A simple calorimeter can be used to measure a change in enthalpy. Enthalpy is an extensive quantity because an extensive quantity depends on the size of the molecule or the number of moles (how much of the molecule you have). Therefore think of a handful of gunpower vs. a storage room full of gunpower. Which reaction will have more enthalpy change? Yes, the room full of gunpower because there is more gunpowder in the reaction. This is an example of why enthalpy is an extensive quantity. Hope you understand now.

Q6. What is the difference between enthalpy change and molar enthalpy?

Answer: Enthalpy change is for a specific quantity of reagent (eg. in grams). Molar enthalpy change is for the number of moles in the balanced equation.

Q7. What is an exothermic reaction? Is the change in enthalpy positive or negative?

Answer: In this process bond breaking always requires energy while bond making always release energy. The balance between these two processes result in two types of reactions exothermic and endothermic reaction. When the energy released by bond forming is greater than the energy consumed by bond breaking there is a net release of chemical energy. This type of reaction is called exothermic reaction+ it is a chemical reaction that releases energy in the form of light or heat.

Q8. What is an endothermic reaction? Is the change in enthalpy positive or negative?

Answer: An endothermic reaction is a chemical reaction in which energy (heat, light, etc.) is absorbed instead of being released as it is in a exothermic reaction. It may also be called a hypothermic reaction.

Q9. What is the difference between heat and temperature?

Answer: 1. Heat is the energy transferred from one material to another. Temperature is the average kinetic energy of it's particles. 2. Heat can change the state of particles; for example, if the substance is ice and you add heat, it would melt the ice to water. Temperature does not do this. 3. Heat is the transfer of energy from particles of a warmer object to the particles of a cooler object. This is not what temperature is. 4. Heat is energy while temperature is not. 5. Heat is measured in Joules; temperature is measured in degrees Celsius or Fahrenheit. 6. temperature actually measures how much heat there is.

Q10. Define an exothermic reaction and an endothermic reaction. Give an example of each.

Answer: Endothermic reaction: sunlight + 6CO₂ (g) + H₂O (l) = C₆H₁₂O₆ (aq) + 6O₂(g) which is the equation for photosynthesis.

An exothermic reaction is a reaction that releases heat. An exampleof this is the burning of methane, CH₄ + 2O₂ → CO₂ + 2H₂O.