Unit 2 : Matter & Energy
What are signs of a chemical change?
- fizzing or bubbling (not heating, like boiling) - smoke produced - heat produced - color change - turns cloudy/forms a precipitate - new odor is formed
How many joules are in a kilojoule
1000 J = 1 kJ
How many calories are in a kilocalorie
1000 cal = 1 kcal
How many joules are in a calorie
4.184 J = 1 cal
What are the separation methods?
Evaporation for homogeneous mixtures Filtration for heterogeneous mixtures *Compounds can be separated into elements by chemical methods
specific heat capacity unit
J/g*C
Matter: Mixture vs Pure Substance
Matter Mixture Pure Substance homo hetero element compound (same) (not same) Mg NacL AKA: solution H2O alloy
Formula for heat energy
Q= mcp △T
cool substance △T formula
Tf - Ti
hot substance △T formula
Ti - Tf
define: molecule
a collection of atoms bonded together that behave as a unit
define: solution
a homogeneous mixture
define: heterogeneous mixture
a mixture containing regions with differing properties
define: alloy
a mixture that has metallic properties
define: homogeneous mixture
a mixture that is the same throughout
define: mixture
a substance with variable composition
define: solubility
amount of solute that dissolves in a given amount of solvent at a certain temperature. (Physical property)
define: unsaturated
can hold more solute
define: chemical change
change in which a substance becomes a different substance EX: Reaction
define: physical change
change that does not affect the composition of a substance EX: Ice melting to liquid. NacL + H2O to make a SOLUTION
define: physical property
characteristic of a substance that can change without the substance becoming a different substance EX: color, odor, mass, melting point
define: chemical property
characteristic that describes the ability of a substance to change to a different substance EX: sulfur forms a gas that smells when it burns - sulfur dioxide
define: pure substance
either a pure element or a compound
define: law of conservation of energy
energy cannot be created or destroyed, but it can be converted from one form to another
define: heat
flow of energy due to a temperature difference
define: atom
fundamental unit of which elements are made
density unit
g/ml or g/cm3
super saturated
holds more solute than normal
define: saturated
holds the maximum amount of solute
hot substance to cool substance formula
hot substance cool substance lose heat = gain heat mcp△T = mcp△T
define: endothermic
refers to a process in which energy (as heat) flows from the surroundings into the system -> system requires heat
define: exothermic
refers to a process in which energy (as heat) flows from the system to the surrounding -> system produces heat
define: element
substance containing only 1 type of atom
define: liquid
substance with a definite volume that takes the shape of its container
define: solid
substance with a fixed shape and volume
define: gas
substance with no definite shape or volume
define: comppound
substances made by bonding atoms together in particular ways. Contains 2 or more DIFFERENT atoms
define: matter
the "stuff" of which the universe is composed. It has 2 characteristics: has mas and occupies space (volume)
define: energy
the ability to do work or produce heat
define: specific heat capacity
the amount of energy needed to raise the temperature of the gram of a substance by one celsius degree
define: temperature
the measure of the random motions of the components of a substance
