Basic concepts-energy and matter

Chemical Energy

Contained in the bonds between atoms and molecules, such as food or a car battery.

Difference between physical and chemical properties/changes

A physical property is an aspect of matter that can be observed or measured without changing it. Examples of physical properties include color, molecular weight and volume. A chemical property may only be observed by changing the chemical identity of a substance. This property measures the potential for undergoing a chemical change. Examples of chemical properties include reactivity, flammability and oxidation states.

Nuclear Energy

The energy released when the nuclei of "heavy" atoms, such as Uranium, are split (a process called nuclear fission) or it is released when the nuclei of "lighter" atoms, such as hydrogen, are joined (a process called nuclear fusion)

Entropy Changes (2nd law of thermodynamics)

The laws of thermodynamics describe the relationships between thermal energy, or heat, and other forms of energy, and how energy affects matter. The First Law of Thermodynamics states that energy cannot be created or destroyed; the total quantity of energy in the universe stays the same. The Second Law of Thermodynamics is about the quality of energy. It states that as energy is transferred or transformed, more and more of it is wasted. The Second Law also states that there is a natural tendency of any isolated system to degenerate into a more disordered state.

Mechanical Energy

the energy of motion (Kinetic and potential)

Thermal Energy

the heat energy of a substance or system and can be measured by a thermometer.

Electrical Energy

The energy carried by the flow of electrons in an electric conductor.

Energy transformations

Energy is the capacity to do work. It cannot be created or destroyed but it can and is transferred and transformed from one form to another. There are 6 forms of energy. Chemical Electrical Mechanical Nuclear Radiant Thermal

Kinetic and Potential Energy

Now that the kinetic energy and potential energy have been defined, we can now apply the Law of Conservation of Energy. In other words, the kinetic energy plus the potential energy equals a constant (KE+PE=Constant). Let's imagine a simple energy problem. There is an object that travels from one point to another. We will call the first point the starting point (1), and the second point the ending point (2). Without considering anything else we can set up the basic equation as KE1+PE1=KE2+PE2. Let's simplify this even more; let's say the object starts at rest (KE1=0) and let's say we define the datum at the ending point (PE2=0). Now we can say that PE1=KE2. The energy has literally been converted from potential energy to kinetic energy. Note that the total energy at point 1 is equal to the energy at point 2, the energy has changed forms, but was not created or destroyed.

Conservation of Energy (1st law of thermodynamics)

The First Law of Thermodynamics states that heat is a form of energy, and thermodynamic processes are therefore subject to the principle of conservation of energy. This means that heat energy cannot be created or destroyed. It can, however, be transferred from one location to another and converted to and from other forms of energy.

Radiant Energy

energy is provided by waves found in the EM spectrum. Typical radiant energy waves include light, microwaves and x-rays

Kinetic Energy

energy that comes from motion. In other words, objects that are moving have something that is referred to as kinetic energy. Since kinetic energy is based on motion, it is always a positive value. If it is not in motion, the kinetic energy of that object is zero. Kinetic energy can never be a negative value. Kinetic energy can be quantified as one half of the mass times the velocity squared (KE = 1/2*m*v²). In SI units, the mass should be in kilograms (kg), and the velocity in meters per second (m/s). In English units, the mass should be either pound mass (lbm) or slug, and the velocity in feet per second (ft/sec).

Potential Energy

energy that is related to an object's potential. Potential Energy can be quantified as mass times gravity times height (PE=m*g*h). The unit for mass should be either kilogram or pound mass depending on the unit system. Gravity is a constant, 9.81 m/s² in SI units or 32.2 ft/sec² in English units. Gravity is an acceleration, it can be described as meters or feet per second per second or the change in velocity per second. Lastly, the height, has units of meters in SI units and feet in English units. It is important to note that height is considered a relative quantity. In other words, when looking at potential energy, the first step is to establish a datum or origin. Meaning, an elevation where the height is zero needs to be defined. For example, the floor can be defined as a height of zero. However, the zero point (datum) does not have to be the floor, it can be any point, but it must not be changed once it is defined. It is also important to note that potential energy can be positive, zero or negative. For example, if the datum is defined as the top of a table, and the object is on the floor, that object has a negative potential energy since the height below the top of the table.

Conservation of matter in chemical systems

in any given system that is closed to the transfer of matter (in and out), the amount of matter in the system stays constant. A concise way of expressing this law is to say that the amount of matter in a system is conserved.