Chapter 1 | Notion

<aside> 🗣 Chemistry: study of matter, means anything that has mass and occupied space

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<aside> 🗣 Substance: made of very tiny particles (smallest unit)

three types:
- Atoms
- Molecules (1< atoms bonded/ chemically joined together)
- Ions (charged particles (+/-) ) </aside>

States of matter

	Diagram tips	Attraction between forces	Arrangement/ packing	Movement
Solid	more than 3*2 particles	strong	closely and regularly packed	only curated slowly in fixed positions, cannot move past
Liquid	more than 6, gaps> particles	still strong but weaker than solid	close and irregularly packed	free to move about, can move past
Gas	/	very weak	far apart and regularly packed	move freely and quickly

Kinetic energy (K.E.)
1. In constant and random position
2. higher speed of movement → more K.E
Potential energy (P.E.)
1. weak attraction forces/ increase separation → more P.E.

<aside> 🗣 Amount of energy: Gas > Liquid > Solid

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✅ physical changes, ❎ chemical changes
- no new substances are formed, the composition of a substance does not change

Endothermic	Sublimation (solid to gas)	Boiling/ evaporation/ vapourization (liquid to gas)	Melting (melting point) (solid to liquid)
Exothermic	Deposition/ desublimation (gas to solid)	Condensation (gas to liquid)	Freezing/ solidification (freezing point) (liquid to solid)

Particles absorb energy before and during melting and boiling
- Before: gain K.E. to raise the temperature to the required temperature (m.p./ b.p.)
- During: gain P.E. for overcoming/ weakening the attraction forces between them, become far apart
Particles release energy before and during condensation and freezing
- Before: lose K.E. to lower the temperature to the required temperature (b.p./ f.p.)
- During: lose P.E. when attraction force between them are stronger, bringing them closer

	Evaporation	Boiling
Temperature	Occurs at a wide range of temperatures	Occurs at a defined temperature: boiling point (b.p.)
Particles that may escape	Only foster-moving particles (with more K.E.) near the surface	All particles in the liquid
Observation	❎ Gas bubbles cannot be seen	✅ Gas bubbles can be seen

<aside> 🗣 Sublimation:

directly from solid to gas (without going liquid state)
particles of solid vibrate fast enough to overcome attraction forces and become widely separated and able to move freely and quickly

eg. Iodine, Carbon Dioxide (dry ice), Ammonium chloride

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Physical state of a substance at room temperature (25°C)