Energetics/Enthalpy change

Question 1

What is Enthalpy change?

Answer 1

Enthalpy change, also known as heat of reaction, is the amount of energy a reaction has absorbed or released.

Question 2

What is an endothermic reaction?

Answer 2

An endothermic reaction is any reaction that absorbs more energy from the surroundings than is released.

Question 3

What is an exothermic reaction?

Answer 3

An exothermic reaction is any reaction that releases more energy into the surroundings than absorbed.

Question 4

What are the conditions for any reaction to be considered chemical? Explica

Answer 4

In order for a reaction to be considered chemical bonds need to be broken and formed in order for bonds to be broken energy needs to be absorbed (endothermic) and in order for bonds to be formed energy needs to be released. There are energy changes in a reaction because the reactants are absorbing energy, and the products are releasing it.

Question 5

Name 4 examples of exothermic reactions.

Answer 5

1. Freezing and Condensation
2. Combustion of fuels
3. Neutralization of alkalis and acids
4. Adding water to Concentrated Sulphuric acid

Question 6

Name 5 examples of endothermic reaction

Answer 6

1. Thermal decomposition
2. Photosynthesis
3. Taking a photo with a film(decomposition of silver bromide to silver and bromide)
4. Melting and boiling
5. Dissolving ionic crystals in water (e.g. potassium nitrate)

Question 7

What sign does an endothermic carry

Answer 7

positive

Question 8

What sign does an exothermic reaction carry

Answer 8

negative