constant

(noun)

An identifier that is bound to an invariant value.

Related Terms

Examples of constant in the following topics:

  • Constant Velocity

    • An object moving with constant velocity must have a constant speed in a constant direction.
    • Motion with constant velocity is one of the simplest forms of motion.
    • To have a constant velocity, an object must have a constant speed in a constant direction.
    • Constant direction constrains the object to motion to a straight path.
    • Examine the terms for constant velocity and how they apply to acceleration

  • Constant Pressure and Volume

    • Isobaric process is one in which a gas does work at constant pressure, while an isochoric process is one in which volume is kept constant.
    • A process in which a gas does work on its environment at constant pressure is called an isobaric process, while one in which volume is kept constant is called an isochoric process.
    • An isobaric process occurs at constant pressure.
    • Since the pressure is constant, the force exerted is constant and the work done is given as PΔV.
    • Since pressure is constant, the work done is PΔV.

  • Equilibrium Constant Expression

    • The equilibrium constant is an expression that gives the ratio of reactants and products at equilibrium.
    • This constant is known as the equilibrium constant.
    • Their activity is 1, so they do not need to be written in the equilibrium constant.
    • The larger the value of the equilibrium constant, the more the reaction proceeds to completion.
    • The equilibrium constant,denoted by K, is the ratio of products to reactants at equilibrium.

  • Motion with Constant Acceleration

    • Constant acceleration occurs when an object's velocity changes by an equal amount in every equal time period.
    • An object experiencing constant acceleration has a velocity that increases or decreases by an equal amount for any constant period of time.
    • Assuming acceleration to be constant does not seriously limit the situations we can study and does not degrade the accuracy of our treatment, because in a great number of situations, acceleration is constant.
    • When it is not, we can either consider it in separate parts of constant acceleration or use an average acceleration over a period of time.
    • When you drop an object, it falls vertically toward the center of the earth due to the constant acceleration of gravity.

  • Homogeneous versus Heterogeneous Solution Equilibria

    • The equilibrium constants for homogeneous and heterogeneous solutions need to be calculated differently.
    • The equilibrium constant K for a given reaction is defined as the ratio of the products of a reaction to the reactants, measured at equilibrium.
    • The reaction quotient measured at equilibrium is the equilibrium constant K.
    • When dealing with these equilibria, remember that solids and pure liquids do not appear in equilibrium constant expressions.
    • The equilibrium constant K is simply [Br2], with the concentration of the pure liquid Br2 excluded.

  • Acid Dissociation Constant (Ka)

    • The acid dissociation constant (Ka) is the measure of the strength of an acid in solution.
    • The acid dissociation constant (Ka) is a quantitative measure of the strength of an acid in solution.
    • Ka is the equilibrium constant for the following dissociation reaction of an acid in aqueous solution:
    • The logarithmic constant (pKa) is equal to -log10(Ka).
    • Acetic acid is a weak acid with an acid dissociation constant $K_a=1.8\times 10^{-5}$ .

  • Expressing the Equilibrium Constant of a Gas in Terms of Pressure

    • For gas-phase reactions, the equilibrium constant can be expressed in terms of partial pressures, and is given the designation KP.
    • Up to this point, we have been discussing equilibrium constants in terms of concentration.
    • Our equilibrium constant in terms of partial pressures, designated KP, is given as:
    • Note that in order for K to be constant, temperature must be constant as well.
    • Therefore, the term RT is a constant in the above expression.

  • Inverse Variation

    • Indirect variation is used to describe the relationship between two variables when their product is constant.
    • Knowing that the relationship between the two variables is constant, we can show that their relationship is:
    • where k is a constant known as the constant of proportionality.
    • Revisiting the example of the decelerating car, let's say it starts at 50 miles per hour and slows at a constant rate.
    • Other constants can be incorporated into the equation for the sake of accuracy, but the overall form will remain the same.

  • Specific Heat for an Ideal Gas at Constant Pressure and Volume

    • An ideal gas has different specific heat capacities under constant volume or constant pressure conditions.
    • Specific Heat for an Ideal Gas at Constant Pressure and Volume
    • where the partial derivatives are taken at: constant volume and constant number of particles, and at constant pressure and constant number of particles, respectively.
    • The heat capacity ratio or adiabatic index is the ratio of the heat capacity at constant pressure to heat capacity at constant volume.
    • It is a simple equation relating the heat capacities under constant temperature and under constant pressure.

  • Constant Pressure

    • Isobaric processis a thermodynamic process in which the pressure stays constant (at constant pressure, work done by a gas is $P \Delta V$).
    • An isobaric process is a thermodynamic process in which pressure stays constant: ΔP = 0.
    • Since the pressure is constant, the force exerted is constant and the work done is given as W=Fd, where F (=PA) is the force on the piston applied by the pressure and d is the displacement of the piston.
    • Specific heat at constant pressure is defined by the following equation:
    • A graph of pressure versus volume for a constant-pressure, or isobaric process.