Background: For most substances, when the temperature of the solid is raised high enough, the substance changes to a liquid, and when the temperature of the liquid is raised high enough, the substance changes to a gas. We typically visualize a solid as tiny particles in constant motion held together by attractive forces. As we add heat to the solid, the motion, or the kinetic energy, of the particles increases. At some temperature, the motion of the particles becomes great enough to overcome the attractive forces. The thermal energy that was added to the solid up to this point was absorbed by the solid as kinetic energy, increasing the speed of the molecules. The lowest temperature at which the particles are able to exist in the liquid form is called the melting point .

Situation: As Beth prepared to make caramel apples she put a handful of caramels in her double boiler and began stirring. When her candy thermometer reached 150 degrees Fahrenheit the caramels began to melt.

Question: Was the caramel solid or liquid below 150 degrees?

Situation: As Beth prepared to make caramel apples she put a handful of caramels in her double boiler and began stirring. When her candy thermometer reached 150 degrees Fahrenheit the caramels began to melt.

Question: Was the caramel solid or liquid above 150 degrees?

Situation: As Beth prepared to make caramel apples she put a handful of caramels in her double boiler and began stirring. When her candy thermometer reached 150 degrees Fahrenheit the caramels began to melt.

Question: Was the thermal energy increasing or decreasing as it heated??

Situation: As Beth prepared to make caramel apples she put a handful of caramels in her double boiler and began stirring. When her candy thermometer reached 150 degrees Fahrenheit the caramels began to melt.

Question: Where the particles moving in the solid caramel or standing still??

Situation: As Beth prepared to make caramel apples she put a handful of caramels in her double boiler and began stirring. When her candy thermometer reached 150 degrees Fahrenheit the caramels began to melt.

Question: Where the particles moving in the liquid caramel or standing still??

Situation: As Beth prepared to make caramel apples she put a handful of caramels in her double boiler and began stirring. When her candy thermometer reached 150 degrees Fahrenheit the caramels began to melt.

Question: Where the particles moving faster in as a solid or liquid?

Situation: As Beth prepared to make caramel apples she put a handful of caramels in her double boiler and began stirring. When her candy thermometer reached 150 degrees Fahrenheit the caramels began to melt.

Question: Where the particles moving slower in as a solid or liquid?

Situation: As Beth prepared to make caramel apples she put a handful of caramels in her double boiler and began stirring. When her candy thermometer reached 150 degrees Fahrenheit the caramels began to melt.

Question: Did the kinetic energy increase or decrease as it heated?

Situation: As Beth prepared to make caramel apples she put a handful of caramels in her double boiler and began stirring. When her candy thermometer reached 150 degrees Fahrenheit the caramels began to melt.

Question: What was the melting point of the caramel?

Situation: As Beth prepared to make caramel apples she put a handful of caramels in her double boiler and began stirring. When her candy thermometer reached 150 degrees Fahrenheit the caramels began to melt.

Question: What is the lowest temerature caramel can be a liquid?