Chapter 2
Matter And Change
Types Of Energy




There are different types of Energy.
Chemical energy- The energy that matter
possesses because of the chemical makeup.
Kinetic energy - The energy an object possesses
due to its motion. E.g. anything in motion.
Potential energy- The energy an object has due
to its position relative to other objects. E.g.
when water is formed.


Law Of Conservation of energy states that
in any physical or chemical change,
energy can change form, but the total
amount of energy remains constant.
Specific Heat Capacity (Cp) of a substance
is the amount of heat energy required to
raise the temperature of 1 gm of a
substance by 1 K.
Temperature Scales






Farenheit scales are not used in Chemistry
Recall Chpt 1 where the SI unit for
temperature is the Kelvin K.
The zero point on the Kelvin scale is
designated as absolute zero.
Absolute zero =273.15°C
t(°C) = T(K) – 273.15 K
T(K) = t(°C) + 273.15°C
Class Practice
Convert the following temperatures:
a)765° C
b) -37°C
c) 0°C
d)1200K
e)0K

Conservation of mass



Law Of Conservation Of mass states that the
products of a chemical reaction have the same
mass as the reactants.
Scientific laws explain things, but they do not
describe them
Example: Consider Newton's Law of Gravity.
Newton could use this law to predict the
behavior of a dropped object, but he couldn't
explain why it happened.
Accuracy and Precision



Accuracy
It is a measurement of how
exact it is or how close it is to
the true value.
Suppose you measure the
volume of a solution as 35.7ml
and your lab. partner
measures the same volume as
37.2ml.If the true volume is
36.0ml,then you are more
accurate than your partner’s
measurement.



Precision
How closely several
measurements of the same
quantity made in the same
way agree with one another.
Suppose you measure the
mass of a substance four times
with the same balance and
record measurements as 110
g, 109 g,111 g,110 g.You can
say by looking at these that
your measurements are
precise.
Significant Figures



Zeroes placed before other digits are not
significant; 0.046 has two significant
digits.
Zeroes placed between other digits are
always significant; 4009 kg has four
significant digits.
Zeroes placed after other digits but behind
a decimal point are significant; 7.90 has
three significant digits.
Class Practice
How many significant figures are there in
these?
a)
0.09709 kg
b)
30.8900 g
c)
1000 mg
Perform the following calculations and express in
significant figures.
a) 34.09L-1.235L
b) 1.8940cm × 0.0651 cm.

Homework





Page 68
#1-8
#18-25
Page 71
#1-7 under Test Prep.