Terms in this set (34)
Matter is anything that has both mass and volume (takes up space). A more rigorous definition is: matter is what atoms and molecules are made of. Matter is commonly said to exist in four states (or phases): solid, liquid, gas and plasma. All matter on the Earth is constructed of elements. In total, 118 elements have been observed to date, of which 92 occur naturally on Earth. Each of these elements have distinct chemical characteristics.
The smallest particle that exhibits the unique chemical characteristics of an element is known as an atom. Atoms are composed of yet smaller particles known as protons, neutrons, and electrons.
The number of protons found in the nuclei of the different types of elements is unique and is referred to as the atomic number. All atoms of a specific element have the same number of protons in their nuclei.
number is total mass of protons, neutrons and electrons in a single atom.
A proton is a subatomic particle that has significant mass and contributes a single positive electrical charge to an atom.
also have significant mass but no electrical charge.
are extremely light subatomic particles having a mass that is 1/1840 of a proton. Each electron also has a negative electrical charge.
Protons and neutrons make up the nucleus of an atom. As a result, most of an atom's mass is concentrated in the nucleus. Because protons are positively charged the nucleus has a positive charge equal to the number of these subatomic particles.
Electrons are found orbiting outside the nucleus at various distances based on their energy level. The area occupied by the electrons has a negative charge equal to the number of these subatomic particles.
(cation and anion):An atom or molecule which has lost or gained one or more electrons, giving it a positive or negative electrical charge is called an ion.
A negatively charged ion, which has more electrons than it has protons, is known as an anion.
Conversely, a positively-charged ion, which has fewer electrons than protons, is known as a cation.
Negative ion, more electrons
A positively charged ion with fewer electrons than protons
Some elements can have variants containing different numbers of neutrons. We call these variants isotopes.
Some isotopes are unstable and their nucleus tends to lose subatomic particles forming an element with a lower atomic mass. This process is known as RADIOACTIVE DECAY
A molecule is formed when two or more atoms join together chemically.
A compound is a molecule that contains at least two different elements.
(reactants and products): A chemical reaction is the pathway by which two substances bond together. One such chemical reaction is the reaction of hydrogen (H) with oxygen (O) to form water (H2O)
To write the chemical reaction you would place the reactants (the substances reacting) on the left with an arrow pointing to the products (the substances being formed). Given this information, one might guess that the reaction to form water is written:
H+O → H2O
However there are 2 problems with this chemical reaction. First, both hydrogen and oxygen react with themselves to form the molecules H2 and O2, respectively. These hydrogen and oxygen molecules are much more common. Given this, one might guess that the reaction looks like this:
H2 + O2 → H2O
But we still have one problem. As written, this equation tells us that 1 hydrogen molecule (with 2 H atoms) reacts with 1 oxygen molecule (with 2 O atoms) to form 1 water molecule (with 2 H atoms and 1 O atom). The number of atoms for the reactants and products are not equal. To write a chemical reaction correctly, the number of atoms on the left side of a chemical equation has to be precisely balanced with the atoms on the right side of the equation. How does this happen in our example? In actuality, the O atom that we 'lost' reacts with a 2nd molecule of hydrogen to form a second molecule of water. The reaction is therefore written:
2H2 + O2 → 2H2O
Energy: Energy is one of the most fundamental and universal concepts of physical science, but one that is remarkably difficult to define in way that is meaningful to most people. This perhaps reflects the fact that energy is not a "thing" that exists by itself, but is rather an attribute of matter (and also of electromagnetic radiation) that can manifest itself in various ways. It can be observed and measured only indirectly through its effects on matter that acquires, loses, or possesses it.
is associated with the motion of an object; a body with a mass m and moving at a velocity v possesses the kinetic energy (Ke)
Ke = mv2/2.
: is energy that is stored within an object (system). It exists when there is a force that tends to pull an object back towards some original position when the object is displaced.
The sum total of all of this microscopic-scale randomized kinetic energy within a body is given a special name, thermal energy.Thermal energy is the total kinetic energy of an object due to the random motion of its atoms and molecules. It is sometimes confused with internal energy or thermodynamic energy. They consist of the sum of the kinetic energy (thermal energy) and the potential energy of an object.
Difference Between Temp and Thermal Energy:
Temperature is different from thermal energy. Temperature is related to the average kinetic energy of an object and is therefore not influenced by the mass of the object. Thermal energy is a measure of the total kinetic energy of an object, therefore it is influenced by the object's mass.
is a number that is related to the average kinetic energy of the molecules of a substance. If temperature is measured in Kelvin degrees, then this number is directly proportional to the average kinetic energy of the molecules. So, temperature is not energy. It is, though, a number that relates to one type of energy possessed by the molecules of a substance. Temperature directly relates to the kinetic energy of the molecules. The molecules have another type of energy besides kinetic, however; they have potential energy, also. Temperature readings do not tell you anything directly about this potential energy.
The first law of thermodynamics:
The first law of thermodynamics: states that the energy of a closed system is conserved. Therefore, to change the energy of a system, energy must be transferred to or from the system.The two ways that energy can be transferred are by work and heat transfer.
Heat is (symbolized by Q) is the transfer of thermal energy caused by the temperature difference. The unit for the amount of energy transferred by heat in the International System of Units SI is the joule (J), though the British Thermal Unit and the calorie are still occasionally used in the United States. The unit for the rate of heat transfer is the watt (W = J/s).
Work is the transfer of energy by any process other than heat. Work can take various forms: mechanical, electrical, gravitational, etc.
Heat Transfer (Conduction, Convection, Radiation)
When a warmer body is brought into contact with a cooler body, thermal energy flows from the warmer one to the cooler until their two temperatures are identical. The warmer body loses a quantity of thermal energy, and the cooler body acquires the same amount of energy. We describe this process by saying that "Q joules of energy has passed from the warmer body to the cooler one." In other words, heat is a process; it is not something that can be contained or stored in a body. The transfer of thermal energy (heat) is described by the second law of thermodynamics which states that thermal energy can flow only one direction, from objects of higher temperature to those of lower. As a result of this fact of thermodynamics, natural processes that involve energy transfer proceed in one direction.
Conduction occurs when two object at different temperatures are in contact with each other. Thermal energy flows from the warmer to the cooler object until they are both at the same temperature. Conduction is the movement of heat through a substance by the collision of molecules. At the place where the two object touch, the faster-moving molecules of the warmer object collide with the slower moving molecules of the cooler object. As they collide, the faster molecules give up some of their energy to the slower molecules. The slower molecules gain more thermal energy and collide with other molecules in the cooler object. This process continues until heat energy from the warmer object spreads throughout the cooler object. Some substances conduct heat more easily than others. Solids are better conductor than liquids and liquids are better conductor than gases. You experience heat transfer by conduction whenever you touch something that is hotter or colder than your skin (e.g. when you wash your hands in warm or cold water).
Convection - heat transfer by mass motion (circulation) of a fluid. To understand heat transfer through convection, we must first examine the concept of. Convection is heat transfer by mass motion (circulation) of a fluid. In fluids (liquids and gases), convection is usually the most efficient way to transfer heat. Convection occurs when warmer areas of a liquid or gas rise to cooler areas in the liquid or gas. As this happens, cooler liquid or gas takes the place of the warmer areas which have risen higher. This cycle results in a continuous circulation pattern and heat is transferred to cooler areas. You see convection when you boil water in a pan. The bubbles of water that rise are the hotter parts of the water rising to the cooler area of water at the top of the pan.
Radiation is heat transfer by means of emission or absorption of electromagnetic radiation. Both conduction and convection require matter to transfer heat. Radiation is a method of heat transfer that does not rely upon any contact between the source of thermal energy and the recipient object. For example, we feel heat from the sun even though we are not touching it. Heat can be transmitted though empty space by thermal radiation. Thermal radiation (often called infrared radiation) is a type electromagnetic radiation. Radiation is a form of energy transport consisting of electromagnetic waves traveling at the speed of light. No mass is exchanged and no medium is required.
Buoyancy is the tendency of an object to float in a fluid. Buoyancy is controlled by differences in density between the object and the fluid.
is the heat (transfer of thermal energy) needed to raise the temperature of one gram (g) of a substance one degree Celsius.
Latent heat is the heat (transfer of thermal energy) needed to raise the temperature of one gram (g) of a substance one degree Celsius.
Energy Density-Energy Transfer
Energy density is the amount of energy stored in a given system or region of space per unit volume, or per unit of mass
Diffusion is a consequence of the constant thermal motion of atoms, molecules, and particles, and results in material moving from areas of high to low concentration. Thus the end result of diffusion would be a constant concentration, throughout space, of each of the components in the environment.