Thermodynamics (Heat)

What is Heat? A form of energy that results from the motion of particles in matter Heat energy flows from a warmer object to a cooler object

Sources of Heat Sun (radiant energy) Friction Electricity Chemical reactions that give off heat Nuclear energy gives off heat when atoms split

Radiant Energy Protons radiating from the sun or from another light source

Friction Friction is a form of mechanical energy, the energy of motion, that produces heat

Electricity A form of power created by the movement of electrons. These electrons can form naturally like in static or lightening. They can also be forced into wire conductors and converted to heat (think of electric stoves or thermal blankets)

Chemical Reactions When substances react chemically with each other they can release or take in heat Endothermic-chemical reactions in which heat is absorbed IN Exothermic – chemical reactions in which heat is released out (like EXITing!)

Nuclear Nuclear energy is released when atoms split or are joined together and can produce heat as well as electricity (stars shine because they release nuclear energy!)

How does Heat Affect Matter? Gas Liquid Solid The faster particles move, the more heat energy Solid matter has particles that are close together and not moving very much…usually this means that solid objects might be colder as in the case of ice cubes…but metal can heat up and still stay solid, so that is not always the case. Molecules in liquid are farther apart and adding heat can make the molecules move faster, eventually turning them into a gas as in when you boil water Cold Warm Hot

Expanding & Contracting Matter Heat causes particles in matter to push each other farther apart….this means matter is expanding when heat is added When matter loses heat, the particles move less and are closer together…this means that matter is contracting How might heat affect a bridge, an engine, water? How do hot air balloons use heat to help them rise off the ground?

Can Crushing Experiment

What is Temperature? This is just a measure of how fast the particles of whatever you are measuring are moving Thermometers help us measure temperature Thermometers measure heat in degrees. This can be in Fahrenheit or in Celsius Most scientists use the Celsius scale to measure temperature

Thermometer Activity

Converting Temperature Scales If you have the temperature in Fahrenheit and want to convert to Celsius: (°F - 32) x .56 = °C If you have the temperature in Celsius and want to convert to Fahrenheit: (°C x 1.8 ) +32 = °F

Fo to Co Temperature Conversion Practice

Freezing Point The temperature at which a liquid changes to a solid is its FREEZING POINT Every substance on Earth has its own specific freezing point ….we are most familiar with water’s freezing point because we use water on a daily basis and it is involved in much of our weather

Melting Point The temperature at which a solid changes into a liquid is its melting point Every substance on Earth has its own specific melting point

Boiling Point This is the temperature in which a substance changes from a liquid to a gas Every substance on Earth has its own specific boiling point

Changing Freezing Point & Boiling Point You can change the freezing point and boiling point of substances by mixing them together Example: We put salt (sodium calcite) on the road to melt ice. The salt changes the water’s freezing point so that it can be a lot colder before the water will freeze…making the roads safer for us to drive on!

Penguin Heat article

How Can Heat be Measured? Don’t mix up temperature and heat! They are different! Temperature is a measure of how fast molecules are moving in a substance Heat is measured by using the amount of mass an object has in relation to its temperature.

Measuring Heat Heat is measured in units called calories Heat = change in temperature (oC) x Mass (g) Try it out! How many calories of heat are needed to raise the temperature of 6 grams of water from 5 oC to 15 oC?

Heat = Change in temperature (oC) x Mass (g) First, calculate the Change in Temperature 15 oC - 5 oC = 10 oC Then calculate the heat: Heat = 10 oC x 6g Heat = 60 calories

Cooling To calculate how much an object has cooled you use the same formula that is for heat but your problem is stating that it went from a higher temperature to lower temperature so your answer will be a negative number Example: Suppose you had 10 grams of water that had cooled from 70 oC to 40 oC.

Heat = Change in temperature (oC) x Mass (g) Change in temperature = 70 oC - 40 oC Change in temperature = 30 oC Heat = 30 oC x 10g Heat = 300 calories lost or -300 calories (since heat was lost)

Heat/Calorie Worksheet

How Does Heat Travel?

Radiation The movement of energy (protons) through vacuum (a vacuum is a space that contains no matter, not even air particles) Radiation is from the sun but also from things like fire or light bulbs that radiate heat out around them

Conduction The movement of heat energy from one molecule to the next Hint: Remember con”touch”tion….molecules have to touch in order for conduction to occur! Examples…heating a pan on a stove…the burner conducts heat into the pan. Or a warm kiss from your sweetie can “Heat” up your lips when they touch!

Convection The method of heat movement that happens when the particles of a gas or a liquid rise…as they rise they carry heat

Convection-Conduction-Radiation Practice