Ch 3 Flashcards
Pure Substances
A form of matter that always has a definite and constant composition
Element
- Pure substances that contains atoms of only one type
- The most basic form of matter.
- Each element can be found on the periodic table
Each element has a unique name and is represented by a unique symbol
- Chemical symbol: a one- or two-letter designation for an element derived from the element’s name
- First letter of the symbol is always capitalized
Mixtures
a physical combination of two or more pure substances in which each substance retains its own chemical identity
A mixture is a type of matter that consists of:
- Two or more substances that are physically mixed, not chemically combined
- Two or more substances in different proportions
- Substances that can be separated by physical methods
Homogeneous Mixtures (solutions)
- The composition is uniform throughout
* The different parts of the mixture are not visible
Heterogeneous Mixtures
- The composition of substances is not uniform
- The composition varies from one part of the mixture to another
- The different parts of the mixture are visible
Temperature
- Is a measure of how hot or cold an object is compared to another object
- Indicates that heat flows from the object with a higher temperature to the object with a lower temperature
- Is measured using a thermometer
Conversions between Celsius and Kelvin
- (Temperature in K) = (temperature in oC) + 273
* (temperature in oC) = (temperature in K) – 273
Conversions between Celsius and Fahrenheit
- oF = 9/5 (oC) + 32
* oC = 5/9(oF – 32)
Energy:
- Makes objects move
- Makes things stop
- Is needed to “do work”
Two main forms of energy:
- Potential
* Kinetic
Potential Energy
is energy stored for use at
a later time.
Kinetic energy
energy is the energy of matter in motion.
Energy can take many forms:
Heat Mechanical Light Electrical Chemical Nuclear
Energy is often converted
from one form to another.
Heat (q):
*Most commonly required/released form of energy in chemical reactions
*Always flows from hotter objects to colder objects
Provides kinetic energy from the hot object to the cold object
- The energy lost by the hot object is equal to the energy gained by the cold object
- Units: calories (cal) or Joule (J)
Specific heat (c):
- Quantity of heat energy needed to raise the temperature of 1 gram of a substance by 1 degree Celsius
- Units: J/goC or cal/goC
- The higher the specific heat of a substance, the less its temperature will change when heat is added to it
Calculating Heat
q = m x c x DT DT = T(final) – T(initial)
