summarize module 1: Let Us Study
Getting to know gases and its behavior
Have you ever seen a hot air balloon? Do you wonder 
what makes it fly through the air? Air pressure is a big part 
of how hot air balloons work. To get a clearer 
understanding, let’s compare gas particles to people in a 
crowded dance floor. Too many people too close together 
means there are a lot of collisions. Most of the time a bump 
doesn’t create any problem, but occasionally a collision 
between two couples can be harder than usual. The more 
active the dancing (rock and roll, for example, rather than 
the waltz), the more frequent the possibility of bumping into 
someone else.
Each gas particle is considered to be independent of all other gas 
particles. There are variables used to describe gases: mass, volume, pressure,
and temperature. Gases seem to be weightless, but they are classified as 
matter, which means they have mass. It’s this very low density that allows us 
to be able to walk through the room without concerning ourselves with air 
resistance. In a smaller container, the molecules have less room to move. The 
particles hit the sides of the container more often. Gas pressure results from 
the collisions between gas molecules and the walls of the container they are 
in. More molecules mean more collisions which means more pressure. Gases 
naturally move from areas of high pressure to low pressure because there is 
empty space to move into – a spray can is example.

Unlike couples on the dance floor, a gas particle that collides with 
another gas particle just bounces off with no change in speed, just direction. 
Gas particles don’t respond to heat the same way people do. When we get hot, 
we become less active and just want to sit in the shade with a cool drink of 
water or soda. When gas molecules experience an increase in temperature, 
they get excited and move faster. This concept is known as the KINETIC-
MOLECULAR THEORY which we will dig deeper as we proceed in this lesson.
Let’s investigate if there is interrelationship among properties of gases.
Gas particles have a very weak intermolecular force of attraction, hence 
they move as far as possible from each other. They have the tendency to 
occupy all the spaces they are contained in.

Robert Boyle, an Irish physicist, published his law 
in 1662. His law was based on research involving 
the relationship of the pressure of a gas and volume 
of gas. Based on the findings of the experiment he 
conducted with the J-tube, he concluded that as 
the pressure increases, the volume of a fixed 
amount of gas decreases, forcing the gas particles 
to move closer to one another.

Where:
V= volume, P = pressure, T = temperature and n = amount of the gas 
It is read as: The volume of a gas is inversely proportional to its pressure, if 
temperature and amount of a gas are held constant.
Let’s take a look at the equation again and try to change the proportionality 
sign (α) with the equal sign (=).
The latter equation is simply read as:
The product of Pressure and Volume is constant.
Since volume and pressure of the gas can be varied, let P1 and V1 be the 
initial pressure and volume respectively and P2 and V2 be the final pressure 
and volume respectively.

According to Boyle’s Law, PV= k therefore:
V1 P1 = k
V2 P2 = k
Then, V1 P1 = V2 P2
Let’s try to solve this problem:
The inflated balloon that slipped from the hand of Renn has a volume 
of 0.50 L at sea level (1.0 atm) and it reached a height of approximately 8 km 
where the atmospheric pressure is approximately 0.33 atm. Assuming that 
the temperature is constant, compute for the final volume of the balloon.
In analyzing the problem, it is important that you categorize the initial 
and final conditions of the variables:
By applying Boyle’s Law, can you predict what will happen to the 
final volume? 
Yes, you’re right! The final volume will increase. Let’s compute for 
the numerical value of the final volume by substituting the given 
values to this equation.
V1P1 = V2P2
V2 = V1P1 / P2
V2 = (0.50 L) (1.0 atm)/ (0.33 atm) = 1.5 L
Let us now proceed to another interrelationship among gases.

Jacques Charles, a French scientist, determined 
the relationship between volume and 
temperature of gas. In his experiment, Jacques 
Charles trapped a sample of gas in a cylinder 
with a movable piston in water bath at different 
temperatures. Charles’ Law
states that at constant pressure, the volume of a 
fixed amount of gas is directly proportional to

Mathematically, Charles’ Law can be expressed as:
V α T at constant P
Where: V = volume and T = temperature expressed in Kelvin

Why is there a need to convert °C to K?
Kelvin is the basic unit for measuring temperature in the International 
System (SI). It denotes the absolute temperature scale with absolute zero as 
the starting point - whereby zero Kelvin or absolute zero is theoretically the 
lowest attainable temperature. Kelvin scale is used in gas law calculations 
because the pressure and volume of a gas depend on the motion of the 
particles or the Kinetic Energy (KE) of particles. There is a direct relationship 
between the temperature and the kinetic energy, no other temperature scale 
is based on absolute zero, so zero Kelvin means zero KE. When we double
the temperature in Kelvin, the kinetic energy of gas is also doubled. A change 
in Celsius or Fahrenheit is not directly related to KE as these scales do not 
start at zero.
Removing the proportionality symbol (α) and using the equality 
sign (=) the equation will be as follows:
 V = k T or
Considering the initial and final conditions, we will arrive 
at the following equations:
Whereas, V1 is the initial volume and V2 is the final volume
 T1 is the initial temperature and T2 is the final temperature.
If the volume-temperature ratios are the same in the initial 
and final conditions, then we will arrive at this equation: V_1/T_1 = V_2/T_2


Boyle's law states that the pressure (p) of a given quantity of gas varies 
inversely with its volume (v) at constant temperature.
On the other hand, Charles' law states that that the volume occupied 
by a fixed amount of gas is directly proportional to its absolute temperature, 
if the pressure remains constant.
Let us try to make ourselves familiar with the Kinetic Molecular Theory 
and try to relate the above mentioned concepts with the said theory.
The kinetic-molecular theory is a theory that explains the states of 
matter and is based on the idea that matter is composed of tiny particles that 
are always in motion. This theory is used to explain the behaviors common 
among gases.
Kinetic Molecular Theory of Gases states that:

a. Gases are composed of molecules. 
The distances from one molecule to 
another molecule are far greater than 
the molecules’ dimensions. These 
molecules can be considered as 
spherical bodies which possess mass 
but have negligible volume.
b. Gas molecules are always in 
constant random motion and they 
frequently collide with one another 
and with the walls of the 
container. Collisions are perfectly
elastic- meaning kinetic energy is
transferred without loss from one
particle to another- the total
kinetic energy remains constant.
c. There is a neither attractive nor repulsive force between or among gas 
molecules.
d. Movement of gas molecules is affected by temperature. The average 
kinetic of the molecules is directly related to the temperature of gas.
The Kinetic Molecular Theory (KMT) explains the properties of gases and 
describes the behavior of gases. So far, you have learned that gases have 
mass, volume, temperature and it exerts pressure. The pressure exerted by 
gas molecules is due to collision among gas molecules and with the walls of 
the container. The frequency of collision is affected by temperature because 
gas molecules move faster at high temperature, on the other hand, they 
move slowly at low temperature. The faster the movement of the molecules, 
the more frequent the collision, causing an increase in pressure.