Matter & Change

Chemistry: the study of $matter$ and $changes$ that are associated with it. ex: physical and/or chemical

Properties of Matter: matter is anything that has $mass$ and occupies $space.$

^^5 Indicators of a Chemical Change:^^

• emission of $light$ and/or $heat$
• formation of a $gas$
• formation of a $precipitate$
• change in $color$
• emission of $odor$

All matter can be classified into three groups:

• elements
• compounds
• mixtures

$States of Matter:$

Solid

• has a definite volume and shape
• the particles of a solid are packed close together in relatively fixed positions
• particles are held by very strong forces between them
• the particles of a solid simply vibrate about a fixed position

Liquid

• has a definite volume but no definite shape
• assumes the shape of the container
• the particles of a liquid are held close together but because they are moving faster they can overcome the attractive forces and move one another

Gas/Plasma

• has neither a definite shape nor definite volume
• composed of particles that move very rapidly and are at a great distance from one another, making the attractive forces between the particles very weak
• ==plasma==: a high-temperature physical state of matter in which atoms lose most of their electrons
• can be found in lightning, stars, and some TV screens

$Endothermic vs Exothermic$

==Endothermic==

definition: a reaction that ==releases energy to the surroundings==, causing the reaction mixture and its surroundings to become ==hotter==

examples: burning/combustion, neutralization, and displacement

^^Exothermic^^

definition: a reaction in which ^^energy is absorbed from the surroundings^^, causing the reaction mixture and its surroundings to become ^^cooler^^

examples: evaporating or melting