Analía Bellizzi – Chemistry Classes

Ronald Reagan Senior High School

## Matter: Changes of States

What is necessary to change one state of matter into another?

We will concentrate in the six changes you see in the screen represented with arrows. The blue arrows show that the substance is losing energy. the red arrows represent a gain in energy.

#### STATES OF MATTER BY INCREASING ENERGY

The following is a graph that shows the states of matter by increasing amount of energy from bottom to top.

## Changes, one by one

Liquid to Solid.

#### FREEZING POINT:

The temperature in which a Liquid changes to solid. Example: Water freezes at 0⁰C.

Hint: Compare this with the melting poing!

Solid to liquid.

#### MELTING POINT:

The temperature in which a Solid changes to Liquid. Example: Ice melts at 0⁰C

Gas to Solid.

#### SUBLIMATION:

Solid to Gas.

Some substances do not melt but they pass from  solid to gas directly. this process is called Sublimation

Gas to Liquid.

#### CONDENSATION POINT:

The temperature in which a Gas changes to liquid. Example: Water condenses at 100⁰C.

Liquid to Gas.

#### BOILING:

Liquid to Gas.

Boiling occurs through out all the liquid and only when the liquid reaches the boiling temperature.

#### BOILING POINT:

The temperature in which a liquid turns into a gas. Example: pure water vapor boils at 100⁰C.

#### EVAPORATION:

Liquid to Gas.

Evaporation occurs:

• AT ANY TEMPERATURE
• ONLY ON THE SURFACE
• THE HIGHER THE TEMPERATURE, THE FASTER EVAPORATION.

## Heating Curves

• A heating curve represents the change in temperature and  phase transitions that a substance undergoes as heat is added to it. like in the graph below:

• The plateaus on the curve mark the phase changes (changes in state of matter). The temperature remains constant during these phase transitions.
• The first change of phase is melting, during which the temperature stays the same while water melts.
• The second change of phase is boiling, as the temperature stays the same during the transition to gas.

## Cooling Curves

• A cooling curve represents the change in temperature and  phase transitions that a substance undergoes as heat is taking out from it. like in the graph below:

• The plateaus on the curve mark the phase changes (changes in state of matter). The temperature remains constant during these phase transitions.
• The first change of phase is condensation, during which the temperature stays the same while water condenses from gas to liquid.
• The second change of phase is freezing, as the temperature stays the same during the transition to solid.