physical and chemical changes; rate of reaction

physical change

• easy to reverse

• eg. changing state, making a mixture of substances, disolving solute in solvent

• usually no colour change

• no significant energy change

chemical change

• difficult to reverse

• always new chemical substances formed from original compounds

• colour change

• effervescence (fizzing)

• other signs

  • light

  • smell

    • change in pH

Increased concentration or pressure

increasing concentration/pressure → increased reaction rate

increased surface area

increasing surface area → increased reaction rate

increased temperature

increased temperature → increases reaction rate

using a catalyst

presence of catalyst → increased reaction rate

• the catalyst stays unchange during and after a reaction

collision theory

for a chemical reaction to happen, the reactant particles must collide successfully with each other

• there must be enough activation energy