C7 - Energy Changes Flashcards
What are endothermic and exothermic reactions?
An endothermic reaction takes in energy from it’s surroundings to react, whilst an exothermic gives out energy to react.
What is a practical use for an exothermic reaction?
A hand warmer.
What is a practical use for an endothermic reaction?
An instant cold pack.
What is bond energy?
The energy needed to break the bond between two atoms.
How do you work out the energy change for a chemical reaction?
Take how much energy is needed to break all of the chemical bonds in the reactants, and how much energy is needed to form all of the chemical bonds in the product, perform Reactant Energy - Product Energy = Energy Change
How does a battery work?
Two metals are dipped in salt solution and connected by a wire. The more reactive metal will donate electrons to the less reactive metal, forming an electrical current.
The greater the difference in reactivity between the metals, the higher the voltage produced.
How is hydrogen used as a fuel?
Hydrogen is oxidised to be used as a source of electrons in a battery. This means that the only waste product is water, with no greenhouse gases being produced.
