Physical changes alter the appearance of a material but do not change its chemical composition. Changes in state between solid, liquid, and gas are physical changes caused by adding or removing thermal energy from particles in a substance as temperature increases or decreases. Temperature measures the average kinetic energy of a substance's particles.

1. PHYSICAL CHANGE
A change that alters the form or
appearance of a material but
does not convert the material
into new substances.

2. Every substance contains energy from the movement of its
particles, called thermal energy. The higher the temperature of
a substance, the greater its thermal energy.
Changes in state are physical changes
Image source: http://itl.chem.ufl.edu/2041_u99/lectures/lec_f.html

3. TEMPERATURE
The measure of the average energy of
motion of the particles in a substance is
Image Source: http://www.adelaidehydronicheating.com.au/solarhotwater.html

4. Matter changes whenever energy is
added or taken away.
Energy is added: Solid  Liquid  Gas
Energy is removed: Gas  Liquid  Solid

6. Image source: http://cse.ssl.berkeley.edu/artemis/mission_sunearth_closeup1.html