Introduction to Chemistry and Matter and Energy. Summer’s over Hang tight It’s going to be an exciting ride!. What is Chemistry?. What is Matter? What is Non-Matter?. Why Study Chemistry?. Central, fundamental science. Other sciences used chemistry as their backbone.
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It’s going to be an exciting ride!
What is Matter?
What is Non-Matter?
Scientific laws are the evidence used to support a conclusion. Scientific hypotheses and theories are our best attempts at explaining the behavior of the world, in ways that can be tested by further experiment.
We don\'t prove theories (and hypotheses) true. We just use the observations to convince ourselves (and others) that we have a good idea. Scientists have a lot of confidence in scientific theories, because they know there is a lot of evidence to back them up.
Scientific law: a generalized description, usually expressed in mathematical terms, which describes the empirical behavior of matter.
Scientific laws describe things. They do not explain them.
Causes of uncertainty:
1. All digits 1-9 are significant
2. Zeros between sig. Figs. are always significant
3. Trailing zeros in a number are significant only if the number contains a decimal pt.
4. Zeros in the beginning of a number whose only function is to place the decimal point are not significant.
5. Zeros following a decimal sig fig are significant.
6. A bar over a zero indicates significance
Start counting from the first nonzero digit you find, and count every digit including zero thereafter!
4.7 X 10-5
Calculate the following to the correct number of sig. figs.
34.5 X 23.46
2.61X10-1 X 356
21.78 + 45.86
32.559 X 34.555
1.2 X 4.3
8.08 + 21.98Significant Figures Practice
Multiplication and Division- limit and round to the least number of sig figs in any of the factors.
I.e.- 144.6 X .0023 = ?
Addition and Subtraction Rule- limit and round to least number of decimal places in any of the numbers that make up the problem.
I.e.- 5.42 g + 131.1 g = ?
1 g = 1000 mg
a. if the unit in step 1 is in the numerator, the same unit in step 3 must be in the denominator
b. if the unit in step 1 is in the denominator, the same unit in step 3 must be in the numerator.
Note: since the numerator and the denominator are equal, the fraction must be equal to 1.
5. Check math by canceling your units.
1 m = 1.094 yd 1mile = 1760 yd 1kg = 2.205lbs
Solid Liquid Melting
Liquid Gas Boiling or Evaporating
Gas Liquid _____________
Solid Gas _____________
Gas Solid _____________
Liquid Solid Freezing, solidifying
Rusting, rotting, burning, chemical reaction…
The capacity to do work (the ability to move or change matter)
3. Radiant/ electromagenetic- heat* and light. *We are mainly concerned with heat for this unit.
Energy due to _____________________
Does work by _______________________________________________________________
Flows from hot areas to cold areas
A measure of ________________________________________________________________________
Refers to the intensity of heat in an object
Change in T = Tf –Ti = D T
NOT a form of energy but is a predictor of heat flowHeat Vs Temperature
(atoms / molecules)
Example: electricity lights a bulb: resistance builds up in the tungsen wire, it glows and gives off light and heat; the total energy in the heat and light = the energy in the electricity.
Example: when heat is added to water on a hot plate, that heat energy is absorbed by the water molecules, which move faster and faster (increased kinetic energy higher temperature)
Example: when ice melts to make water during a phase change
Example: when two chemicals are mixed
*On our large scale, we see matter and energy as separate, but matter and energy interconvert at the subatomic level according to Einstein’s Theory of Relativity E=mc2)
c = specific heat for water = 4.18 J/goC
m = mass of sample
DT = change in temperature of sample in oC
DURING A PHASE CHANGE
(evap / condense)
M = mass of sample
Hf = heat of fusion (for water = 334 J/g)
Hv = heat of vaporization (for water = 2260 J/g)
Calorie ProblemsTheoretical values for energy changes during the heating or cooling of a substance, or during a phase change, can be calculated using three basic equations.
The value of Q for any substance can be calculated, but note that each substance has unique values for specific heat capacity (c), heat of fusion (Hf), and heat of vaporization (Hv). Think about it: it’s easier to raise the temperature of some substances than others.
How much heat is needed to melt 5.0 g of water?
Q = mHv
How much water can be vaporized by 3135 Joules?