Section 2.3Section 2.3Properties of Matter

Mass and Energy Mass and Energy ConservationConservationMass cannot be created or destroyedEnergy cannot be created or destroyed5 grams of ice melt into water. What

mass of water results?5 grams of water boil into 5 grams of

steam. What mass of steam results?An object with a certain amount of

energy falls to the floor and stops moving. Where did its energy go?

What is a property?What is a property?A property is basically something an

object has.Taylor has red hair. Therefore, red

hair is a “property” of Taylor, but it could also be a property of James, Kara, and Elsa.

Water has a melting point of 0 degrees Celsius. Therefore the melting temperature of 0 degrees is a property of water. (it could be the property of some other chemical, too)

Vs.

Physical vs. Chemical Physical vs. Chemical propertiespropertiesPhysical property: Something that is

measured or observed about a substance without changing its composition

Chemical property: The way a substance reacts with others to form new substances with different properties.

Examples:◦Physical property: Water has a density of

1.0 g/mL.◦Physical property: Iron conducts electricity.◦Chemical property: Chlorine gas can react

with sodium metal to create table salt.

and

Physical changesPhysical changesPhysical changes affect the

substance, but do not change its composition.

Examples:◦Breaking glass with a hammer◦Grinding wheat into flour◦Melting a solid substance into liquid◦Boiling a liquid into a gas◦Dissolving sugar into water

Chemical changesChemical changesChemical changes cause new

substances with different properties to be created.

Examples:◦Burning gasoline◦Hydrogen gas and oxygen gas

combine to form water◦Burning food on the stove◦Fading paint

and

Reactivity and BuoyancyReactivity and BuoyancyReactivity: The ability of a substance to

combine chemically with another substance◦Sodium metal has a high reactivity. It

desperately wants to react with a substance like chlorine, iodine, bromine, etc.

◦Carbon dioxide has a low reactivity. It could care less about combining with any other compound.

Buoyancy: The force with which a more-dense fluid pushes a less-dense substance upward◦The physics behind why a balloon rises

against gravity