Heating Curves and Thermodynamics

Heating Curves and Thermodynamics

Heating curve of Water…can you label the important temperatures, phases and phase changes?

Heating curve of Water…can you label the important temperatures, phases and phase changes? Ice Solid

Heating curve of Water…can you label the important temperatures, phases and phase changes? 0 Ice Solid

Heating Curve of Water…can you label the important temperatures, phases and phase changes? Melting / Freezing 0 Ice Solid

Heating curve of Water…can you label the important temperatures, phases and phase changes? Liquid Water Liquid Melting / Freezing 0 Ice Solid

Heating curve of Water…can you label the important temperatures, phases and phase changes? 100 Liquid Water Liquid Melting / Freezing 0 Ice Solid

Heating curve of Water…can you label the important temperatures, phases and phase changes? Boiling / Condensation 100 Liquid Water Liquid Melting / Freezing 0 Ice Solid

Heating curve of Water…can you label the important temperatures, phases and phase changes? Vapor Boiling / Condensation 100 Gas Liquid Water Liquid Melting / Freezing 0 Ice Solid

Thermodynamics: The study of energy (i.e. what it is, how it is transformed from one form to another, how it is used to get things done). • As is probably obvious, this term is extremely vague because it covers a huge number of processes that take place in the world. To get an understanding of what this really means, we need to start where we usually do… at the beginning.

Energy:The ability to do work or to produce heat. There are two types of energy: • Kinetic energy: The energy something has when it moves. (i.e. moving objects, moving particles, vibrating molecules, etc) • Temperature is a measure of the particles in an object. We know this from the KMT, which says that the amount of energy is proportional to the temperature (in K). The more the particles in an object move around, the higher the temperature. • Potential energy: Stored energy that’s waiting for its chance to get moving. (i.e. objects that are waiting to fall off of a shelf, energy stored in chemical bonds, etc). • Chemical potential energy: The energy that’s stored in chemical bonds.

One of the main laws that describe how energy behaves in the world is called the law of conservation of energy (also known as the “first law of thermodynamics”): • Energy is never created or destroyed – it can only be converted between potential and kinetic energy. • This means that you can change kinetic energy to potential (and vice-versa), but you can never make the amount of energy go away. • Examples: • You can use the potential energy of the bonds in gasoline in your car to make your car move. • You can use the energy of moving turbines (kinetic) to charge a battery (potential)

How energy moves from one place to another: • Heat (q): The movement of energy from one thing to another through the motion of molecules (thermal energy). • Heat spontaneously moves from hot things to cold. This is why a hot pan can burn you and you can’t burn a hot pan – the energy goes only from the pan to you because it’s hotter. • Heat and temperature are NOT the same thing: Heat is the transfer of energy, temperature is a measure of the kinetic energy of the object once the energy has finished transferring. • Example: If I give you five dollars, the money is what I give you (heat) and your net value is what goes up after you get the money (temperature). Your wealth is not a five dollar bill, but the five dollar bill does affect it.

Work (w): The movement of energy from one thing to another through the motion of larger things (mechanical energy). • When a weight is lifted up a hill, work has been done on it (this is what you’ll learn in physics).

In chemistry, heat is a lot more useful than work because chemistry generally deals with the movement of atoms and molecules a lot more often than it deals with the movement of large machines. • Since heat (energy that’s being transferred through thermal motion) is more important than work (for our purposes), how do we measure it? More definitions of use: • System: Whatever we’re studying. • This can be practically anything. If we are studying what happens when we heat a pan on the stove, the pan will be the system we are studying. • If a system gets energy added to it, the amount of energy it has after the change is positive. Because of this, an endothermic process is any process in which energy is absorbed by the system we’re talking about. • If a system has energy taken away from it, the amount of energy it has after the change is negative. Because of this, an exothermic process is any process in which energy is given off by the system we’re talking about.

Potential Energy Diagrams

Potential Energy Diagrams The amount of energy in the products is greater than the energy in the reactants…. so this process is ENDOTHERMIC. This means the reaction ABSORBS energy • The

Potential Energy Diagrams • The

Potential Energy Diagrams The amount of energy in the products is less than the energy in the reactants…. so this process is EXOTHERMIC. This means the reaction GIVES OFF energy • The

Heating Curves and Thermodynamics