Science notes - Sem 1 2025

Focus 1 – Pops

Chemical change: A chemical change creates a new substance with different properties by rearranging atoms and breaking or forming chemical bonds.

Physical change: A physical change alters the form or appearance of a substance without changing its chemical composition.

Atoms:

·       Everything is made of atoms

·       Too small to see even with a microscope

·       There are many types of atoms

·       When a substance contains one type of atoms it is an element

·       They are the smallest stable building block of all matter

·       Made of subatomic particles

• Protons

• Neutrons

• Electrons

·       Protons and neutrons are in the centre of the atom which make up the nucleus

·       Protons (+) and electrons (-) have equal, but opposite charges, whereas neutrons are neutral

Synthesis: Combine or make something from simpler parts = AB->A+B

Decomposition: To break down something more complex into simpler components =  X+Y->XY

To test for:

Oxygen (O₂) - Burnt splint

Hydrogen (H₂) - Pop

Carbon dioxide (CO₂) – Limewater

Diatonic: Two for the same atom

Chemical Reactions:

• Atoms are rearranged in chemical reactions

• React - Reactants

• Products - Those formed

• Reactants change into products - involve interaction

• Properties of products are different from reactants

• Heat is often necessary but not always

• Happen at different speeds - Rate

• Reactions happen when particles interact/collide

Particle collision

• In particle collision electrons are rearranged depending on energy involved

• If energy in a collision is high enough the particles can break bonds and form new bonds as different substances

• Particle collisions are constantly occurring - during reactions reactants turn into products

• The time for reactants to fully react depend on how many collisions occur every seconds

• If there aren't many collisions the reaction will be slow, if there are a lot the reaction will be fast

Independent variable: The variable I change in a experiment

Dependant variable: What your measuring

Control variable: The variable that stays the same