Section 2.3 Properties of Matter

Mass and Energy Conservation Mass cannot be created or destroyed Energy cannot be created or destroyed 5 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? 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 properties Physical 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: ◦P◦P hysical property: Water has a density of 1.0 g/mL. ◦P◦P hysical property: Iron conducts electricity. ◦C◦C hemical property: Chlorine gas can react with sodium metal to create table salt.

and

Physical changes Physical 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 changes Chemical 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 Buoyancy Reactivity: 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