Chemistry concepts

Chemical:

• Any substance that has a definite composition

• Is dinitrotoluene a chemical?

• Is water a chemical?

• Is salt a chemical?

Chemical reaction• Process where one or more

substances change to produce new substances

Matter:

• Anything that has mass and takes up space

Mass:

Volume:

• How much space something takes up.

States of matter:

• Solid:• Has a fixed volume and shape• Molecules are closely packed and vibrate (Brownian

motion)

• Liquid:• Has a definite volume, no fixed shape• Molecules spread apart and move past one another

• Gas:• Has no fixed volume. Will occupy any given area.• Molecules are far apart and move rapidly.

Solids and gases can be compressed, not liquids.

Physical property:

• Characteristics of a property, such as• State of matter• Mass• Volume• Density• Color• Odor• Taste• Temperature

• Melting point—solid to liquid

• Boiling point—liquid to gas

• Freezing point—liquid to solid

• Sublimation—solid to gas

• Malleability• Flexible or stiff (rigid)

• Clarity• Transparent, translucent, opaque

• Viscosity • Viscous or runny

• Ductility and compressaibility

• Ductile=able to be stretched into thin wires•

•Conductivity—electrical or temperature

•Luster—shiny or dull

• Solubility—ability to be dissolved• Soluble=can dissolve • Insoluble=cannot dissolve

Intensive property:

• Does NOT depend on amount of substance• Color

• Density

• Temperature

• Melting point, boiling point

Extensive property:

• Does depend on amount of substance• Mass

• Volume

• Heat capacity

Chemical properties• If and how a substance reacts with other

substances, such as• Oxygen• Water• Acid• Light• Combustability

How does matter change?

Can be physical or chemical

Physical change:

• Change in state of matter

• Chemical properties stay the same

• No bonds are broken

Examples of physical changes:

• Change in state of matter• Evaporation• Vaporization• Dissolving• Melting

• …and of course if you rip something, compress something, change shape.

Chemical change

• Bonds are broken

• Substances change into new substances

• Original properties are changed or lost

Indicators that a chemical change (reaction) has occurred:

• New substances are formed:• New color

change• New gas is

produced• Odor produced• Precipitate—solid

that is produced when 2 liquids are mixed

• Energy is released:• Temperature

change• Light is given off• Sound produced• electricity