Chapter 2 Matter & Energy
2-1 Energy
Objectives: A. Know that physical & chemical changes involve energy changes
Energy-ability to do work (energy is always involved in change in matter
whether physical or chemical changes)
Energy is either applied to change matter (endothermic) or released
(exothermic)- melting (energy applied-endothermic) freezing (energy
released- exothermic) evaporation (surface molecules absorb enough
energy to overcome attractive forces and turn into a gas)
B. Law of conservation of energy
Energy of reactants = energy of products (can not be created or
Destroyed but can change forms-chemical-mechanical-light-heatelectrical-sound)
C. Distinguish between heat & temperature
Heat flows from higher to lower temperatures
Chemicals can contain stored energy (potential) kinetic energyenergy do to an objects motion
Temperature is a measure of the average kinetic energy of the
particles in an object
D. Convert between Celsius, Kelvin and Fahrenheit
Celsius (based on the melting and boiling point of water and used
in the lab) C = K- 273.15 Kelvin (SI unit) K = C + 273.15
Absolute zero (when all molecular motion stops = 0K)
C to F C(1.8) + 32
F to C F-32/1.8
100(1.8) + 32 = 212 F (boiling pt of water)
Transfer of heat may not affect the temperature as in melting and
boiling. Ice melts when it continues to absorb energy, but the temperature will not
increase, stays at 0C until all melted. The energy being absorbed is used to pull molecules
away from each other. Water boils at 100C and will stay at 100C throughout the boiling
process.
Specific Heat- a measure of a substance ability to absorb heat energy (amount of heat
needed to raise 1 gram of a substance 1 degree C) Cp (specific heat) = J/g K J= joules
(SI unit for heat energy) Cp of aluminum = 0.897 J/g K and water = 4.18 J/g K
2-2 Studying Matter and Energy
Objectives: A. Know the Scientific Method
Scientific Method- strategy for solving problems- Refer to
Fig 8 pg 46
B. Control conditions in an experiment
Experiments-scientific ideas are tested
C. Know differences between hypothesis, theory, and law
Hypothesis- reasonable and testable explanation for observations
Theory-a hypothesis that withstands repeated testing and can be
disproved.
Law- a statement or mathematical expression that reliably
describes a behavior
Models- are used a help explain hard to understand facts
2-3 Measurements & Calculations in Chemistry
Objectives: A. Distinguish between accuracy and precision
Accuracy – how close the measurement is to the true or actual value
Precision- how close the measurements are to each other
B. Determine significant figures and know rules
Sig Figs- your answer can not be more accurate than the numbers you
are using to solve the problem. Know rules on pg 57 and 58
C. Calculate thermal heat problems using the formula J = m(∆T)Cp
D. Scientific notation-putting numbers in powers of ten (6.023 x1023)