Notes

A welding torch produces a flame by burning acetylene fuel in the presence of oxygen. The energy released from the acetylene fuel is then used to melt a metal.
Which energy transformation happens during this process?
Chemical energy turns into thermal energy.


A generator contains a coil that spins to produce an electric current. How is energy transformed by using a generator?
Mechanical energy is transformed to electromagnetic energy.

Which statement describes mechanical energy?
the sum of the kinetic energy and the potential energy of an object

Which statement is correct about the law of conservation of energy?
As gravity makes an object fall down toward the ground, energy becomes kinetic energy.
Energy is transferred when atoms are rearranged.

What happens to energy when Sally kicks a soccer ball?
Kinetic energy is transferred from the leg to the soccer ball.

A book is falling from the top shelf of a bookcase. Which statement correctly describes the change in the energy of the book?
The potential energy decreases as kinetic energy increases.

As gravity makes an object fall down toward the ground potential

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

In a roller coaster, a car has X joules of potential energy when it is resting at the top of the hill. The car moves downhill and reaches the bottom of the hill, where it moves quickly. Assuming no friction, what does the law of conservation of energy predict about the car?
at the bottom, the car has X joules of mechanical energy

When ammonium chloride is dissolved in water, the beaker gets cold. Which type of reaction does this describe?
endothermic

The temperature of a gas is increased. Which statement best explains the effect that this has on the motion of gas particles?
The average kinetic energy increases, and the particles collide more frequently.

Which reaction is endothermic?
6CO2 + 12H2O+ energy --> C6H12O6+

A baker touches a pie right after taking it out of the oven. Which statement best explains why the pie feels hot?
Molecules in the pie move faster than molecules in the skin, so heat is transferred to the skin.

A hot metal plate at 150°C has been placed in air at room temperature. Which event would most likely take place over the next few minutes?
The air molecules that are surrounding the metal will speed up, and the molecules in the metal will slow down.

Two cups of coffee, one that is at 10°C and one that is at 20°C, are mixed. Which statement about the temperature of the mixture is correct?
Energy is transferred from faster moving molecules to slower moving molecules, and the result is the average of 15°C.

Which direction does thermal energy flow in the following diagram?
heat flows from hand to ice cream

An ice cube is dropped into a glass of milk at 20°C. Which statement explains the transfer of kinetic energy (KE)?
Because milk has higher KE than ice, KE is transferred from the milk to the molecules of ice.

Sulfur reacts with oxygen to form sulfur dioxide (SO2(g), mc010-1.jpgHf = –296.8 kJ/mol) according to the equation below.
What is the enthalpy change for the reaction?
Use mc010-3.jpg.
–296.8 kJ

Ammonia, NH3 (mc013-1.jpgHf = –46.2 kJ), reacts with oxygen to produce water (mc013-2.jpgHf = –241.8 kJ) and nitric oxide, NO (mc013-3.jpgHf = 91.3 kJ), in the following reaction:
What is the enthalpy change for this reaction?
Use mc013-5.jpg.
–900.8 kJ

The enthalpy of formation of water is –285.8 kJ/mol. What can be inferred from this statement?
Heat is released during the process.

Butane C4 H10 (g),(mc016-1.jpgHf = –125.7), combusts in the presence of oxygen to form CO2 (g) (mc016-2.jpgHf = –393.5 kJ/mol), and H2 O(g) (mc016-3.jpgHf = –241.82) in the reaction:

What is the enthalpy of combustion, per mole, of butane?
Use mc016-5.jpg.
–2,657.4 kJ/mol

Which graph is exothermic?
Higher on left goes down to right

Hydrogen reacts with chlorine to form hydrogen chloride (HCl (g), mc012-1.jpgHf = –92.3 kJ/mol) according to the reaction below.
The enthalpy of the reaction is –184.6 kJ, and the reaction is exothermic.

Ammonia (NH3 (g), mc009-1.jpgHf = –45.9 kJ/mol ) reacts with oxygen to produce nitrogen and water (H2 O(g), mc009-2.jpgHf = –241.8 kJ/mol) according to the equation below.
–1,267.2 kJ

What is enthalpy?
the total heat content of the system

What is the enthalpy of the overall chemical equation NO(g) + O(g) mc015-2.jpg NOmc015-3.jpg(g)?
-304.1 kJ

When two intermediate chemical equations are combined, the same substance that appears in the same phase can be canceled out, provided that
it is a reactant in one intermediate reaction and a product in the other reaction.

In the final chemical equation, HF and are the products that are formed through the reaction between Before you can add these intermediate chemical equations, you need to alter them by multiplying the
second equation by 2 and reversing the first equation.

In the final chemical equation, NaCl and Omc006-2.jpg are the products that are formed through the reaction between mc006-3.jpg and Clmc006-4.jpg. Before you can add these intermediate chemical equations, you need to alter them by
multiplying the first equation by 2.

The equation CaCO3(s) mc019-1.jpg CaO(s) + CO2(g) shows the decomposition of calcium carbonate. mc019-2.jpgH = 178.3 kJ/mol, and mc019-3.jpgS = 160.5 J/(molmc019-4.jpgK). The free energy change for the reaction is 130.5 kJ/mol.

Which correctly states the temperature at which the reaction took place and whether the reaction is spontaneous or nonspontaneous?
297.8k non

Which process is spontaneous?
spreading of a strong fragrance of perfume in a room

Which process involves a decrease in entropy?
water freezing into ice

Which process or processes produce an increase in entropy?
iii only

Which process involves an increase in entropy?
ice melting into liquid water

What is the mc021-4.jpgGrxn of this reaction, and would it be spontaneous or nonspontaneous at 300.0 K? Use mc021-5.jpgG = mc021-6.jpgH – Tmc021-7.jpgS.
-100 spontaneous