Untitled Flashcards Set

Science notes, sem 1, 2025

Definitions:

Physical change: changes appearance 

Chemical change: new substance 

• indication: shape, temp, colour, light, sound

Types of reactants:

Synthesis: A + B → AB

• Eg. magnesium + oxygen → magnesium oxide

Decomposition: AB → A+B 

• Eg. water → hydrogen + oxygen

Reaction Rate:

Effect of concentration 

• The more the concentration, the faster the reaction rate 

• Increasing the amount of particles - more likely to react

Effect of surface area

• The more surface area reached, the faster the reaction rate 

• Increasing the amount of particles - more likely to react

Effect of temperature

• The higher the temperature means typically a faster reaction rate

• More energy - more likely to react

Effect of agitation

• The more agitation, the faster the reaction rate  

• More energy - more likely to react 

Effect of catalyst

• When used, the catalyst is left over, not consumed

• Makes the activation energy lower, so it’s easier and faster for the reaction to happen

Collision theory:

• Particles must collide to react

• Particles must have sufficient energy to break and make bonds

• Particles must collide at correct orientation 

Validity:

A - aim tests and measure what it intended

C - Control and controlled variables

E - equipment appropriate

R - range for IV

Reliability:

R- repeat at least 3x

E - exclude outliers

A - average consistent results

C - consistency

Accuracy:

Precise equipment used appropriately

Expected results - are results true to the accepted/expected value 

Aim writing: refer to independent and dependent variables

Line and column graphs: usually have dependent on Y-axis and independent on X-axis 

How to test for:

• 1H2 - Pop test

• CO2 - limewater turns cloudy

• O2 - relight a glowing splint 

Exothermic:

• Gives of energy (usually heat - the surroundings heat up) into its surroundings eg. fire

• Energy in reactants is higher than the energy in the products 

  • The difference between the energy in reactants and energy in products is the energy released

  • The curve is called the activation energy

• Temperature gets hotter

Endothermic:

• Takes in energy as heat from its surroundings eg. melting ice 

• Energy in products is higher than energy in reactants

  • The difference between the energy in reactants and energy in products is the energy absorbed

  • The curve is called the activation energy

• Temperature gets colder