Energy Change

What is enthalpy?

• energy that released into surroundings

• energy that is absorbed from earth

• energy that is stored in all substances within a chemical system

• energy that will disappear ultimately

Which of the following is true about endothermic reaction?

• it absorbs heat energy into the system

• it always have a positive value of change of enthalpy

• The energy of products is less than the energy of reactants in this reaction

• It usually releases heat into surroundings

A good example of exothermic reaction is...

• fireworks

• melting ice blocks

• cooking eggs

• photosynthesis

The unit for the heat change that is measured in a reaction is ________________

A key factor (s) that will influence the quantity of energy exchanged in a reaction is...

• physical states of the reactants and products

• chemical states (nature) of the reactants and products

• amount of the substances

• whether the reactants or products have high heat energy inside them already

The reaction of sodium hydroxide and water is exothermic, this means______

• we can feel the tube is getting warm

• we can feel the tube is getting cool

• the energy is released as heat into surroundings

• the energy is absorbed as heat from surroundings

Which of the following is NOT exothermic? (select all applies)

• combustion

• vaporisation

• freezing

• neutralisation

• boiling

Exothermic reaction usually have some features, they are_______

• baking bread is a good example

• releasing heat into surroundings

• having a positive change of enthalpy value

• more commonly occurred compared to endothermic reaction

Complete the word equation. Change of Enthalpy = _______________ - ______________

Which of the following (in terms of energy) do you think is true when a substance changes from solid to liquid?

• more energy is stored in solid phase than liquid phase

• more free particles that can move freely at liquid phase

• solid phase has more particles at fixed position

• such solid to liquid phase change is called melting, and it should be endothermic reaction