Chemistry 2 - Energy
Consider the generic chemical equation below. X + Y → W + Z Reactant X contains 199.3 J of chemical energy. Reactant Y contains 272.3 J of chemical energy. Product W contains 41.9 J of chemical energy. If the reaction loses 111.6 J of chemical energy as it proceeds, how much chemical energy must product Z contain?
318.1 J
Describe the energy transfers and transformations that occur when a person rides a bicycle. Make sure to identify each example as an energy transfer or an energy transformation.
Include: chemical energy transformed to kinetic energy in muscles and/or body kinetic energy transferred from legs to pedals kinetic energy transferred from pedals to wheels kinetic energy transformed to thermal energy due to friction (wheels get warm) chemical energy transformed to thermal energy in muscles
What happens to energy when Sally kicks a soccer ball?
Kinetic energy is transferred from the leg to the soccer ball
Object A has 604 J of kinetic energy and 285 J of gravitational potential energy. Object B has 481 J of kinetic energy and 300 J of gravitational potential energy. Which object has more mechanical energy?
Object A has more mechanical energy
Which has more mechanical energy, a box on the top shelf of a closet or a box of equal mass on the floor?
The box on the shelf has more mechanical energy because it is higher above Earth's surface
An arrow is fired at a target on a high wall. Which statement correctly describes the change in the energy of the arrow as it moves toward the target?
The kinetic energy decreases as potential energy increases.
open system
a system that can exchange both matter and energy with its surroundings
closed system
a system that can exchange energy, but not matter, with the surroundings
Old photographic flashbulbs burn magnesium metal in a reaction that causes a flash of brilliant white light. A photographer would need to take care not to suffer burned fingers when trying to replace the hot bulb. What best identifies the energy transformation that occurs in the flashbulb?
chemical energy to electromagnetic energy and thermal energy
In a chemical reaction occurring in an open beaker, the reactants have a mass of 10.0 g and contain 1000 J of energy. The products in the beaker contain a mass of 5.0 g and 500 J of energy. Which best explains the difference in energy and mass as reactants are converted to products?
law of conservation
As gravity makes an object fall down toward the ground, ____________ energy becomes kinetic energy.
potential
Which energy change best relates to a boulder that is rolling down the side of a hill?
potential energy transforming into kinetic energy
Thermal energy is the energy associated with
temperature.
joule
the SI unit of energy
energy
the ability to do work or cause change
electromagnetic energy
the energy associated with electric fields, magnetic fields, and electromagnetic radiation
kinetic energy
the energy associated with movement
potential energy
the energy associated with position
chemical energy
the energy stored in chemical bonds
Which statement describes thermal energy?
the energy that is associated with temperature
thermal energy
the kinetic energies of the molecules making up a substance; energy that can flow as heat
law of conservation of energy
the law stating that energy cannot be created or destroyed, but it can change from one form to another
mechanical energy
the sum of the kinetic and potential energy of an object
heat
the transfer of kinetic energy between molecules as faster-moving molecules collide with slower-moving molecules; energy that flows from a warmer object or substance to a cooler object or substance
Which form of energy is directly related to the measure of the average kinetic energy of the particles in a substance?
thermal energy
