Matter & Energy - Ms Brown's Chemistry Page

```Chapter 2

Energy is the capacity to do work
 Potential Energy: energy due to position
 Kinetic energy: Energy due to motion

How does this relate to chemistry?
 Motion of matter (vibrate, flow or collide)
 Stored energy in bonds
▪ When the bonds are broken, energy is either released
(exothermic) or absorbed (endothermic).
 Law of Conservation of Matter
 Matter can not be created or
destroyed, it only changes form

System is a piece of
universe we are
studying

Temperature is a measure of the average
kinetic energy of particles in a substance.
 Misconception: temperature is NOT how hot or
cold something is.


Use the Kelvin scale in science – absolute zero
To convert from oC to K
 K = oC + 273
 oC = K - 273

Hypothesis – reasonable and testable
explanation of observations

Theory – well tested explanation of
observation (results are easily reproducible)

Scientific Law – description of the natural
world that has proven reliable over time
Accuracy is how close a value is to the correct
or accepted value.
Precision is how close a series of
measurements are to each other.
Why are both accuracy and precision
important in the lab?
Significant figures are important when we
measure something. It tells us how accurate
our tools are.
When an object is measured there is always a
degree of uncertainty in the last value
because it is always an estimated value.





Any non zero digit is significant.
Zeros between significant figures are
significant.
Zeros at the end of a number and to the
right of a decimal are significant.
Zeros in front of non zero digits are not
significant.
Zeros at the end of a number with no
decimal are not significant.


Used to write very small or very large numbers
(easier to write and less likely to make mistake
by leaving off or adding extra zeros)
Rules
If number is greater than 1, you have a positive
exponent. (move decimal to the left to create
number between 1 and 9.9)
If number is less than1, you have a negative
exponent. (move decimal to the right to create
number between 1 and 9.9)
```