Thermochemistry Unit

Which one of the following is an endothermic process?

ice melting

What type of chemical reaction releases energy?

exothermic

A substance that heats up relatively slowly has a _______

high specific heat capacity.

What is the term for the phase transition from solid to gas?

Sublimation

Which of the following statements is true?

Adding energy during a phase change increases the space between molecules in a substance.

How does the amount of heat energy change as a 250-g sample of water is heated from 5.0°C to 30.0°C?

As the temperature increases, the amount of heat energy increases.

To calculate the amount of heat absorbed when a substance melts, which of the following is needed?

Change in temperature

What is the term for the phase transition from gas to liquid?

Condensation

What is the term for the phase transition from gas to solid?

Deposition

Adding kinetic energy to a substance _________

Increases the motion of the particles that make up the substance, which raises the temperature.

For the formula: Q = mCpDT, the units for specific heat are ____________.

J/g°C

Which statement correctly describes the energy changes that take place when a solid changes to a liquid at constant temperature?

The potential energy increases and the kinetic energy remains constant.

Which is true for an exothermic reaction?

The products have less potential energy than the reactants.

Gold is a metal with a much smaller specific heat capacity than aluminum. If identical samples of gold and aluminum are exposed to identical amounts of energy, which of the following represents the most likely set of observations?

The temperature change of the gold will be greater than the temperature change of the aluminum.

On a phase diagram, the intersection of the solid, liquid, and gas lines is known as the...

tri-point

Adding potential energy to water _________

Disrupts the hydrogen bonds and causes the molecules to move farther apart.

What is the relationship between temperature and kinetic energy?

Direct

In an exothermic chemical reaction, __________

Energy is transferred from the reaction to the surroundings and ΔH

What is the term for the phase transition from liquid to gas?

Evaporation

What is the term for the phase transition from liquid to solid?

Freezing

What happens on a molecular level when H2O changes phase as heat is added?

Hydrogen bonds are broken and the molecules spread out.

The energy needed to change a liquid to a gas and vice versa, without any change in temperature is called ____.

Latent Heat

Lead (Pb), water (H2O), sulfur (S) and arsenic (As) have specific heats of 0.128 J/g°C, 4.18 J/g°C, 0.706 J/g°C, and 0.329 J/g°C, respectively. Which of these would require the smallest amount of heat to increase its temperature by 10°C? (assume all samples have the same mass)

Lead because it has the lowest specific heat.

Which two properties determine the amount of energy needed for a phase change?

Mass and Latent Heat

What is the term for the phase transition from solid to liquid?

Melting

What happens a molecular level when H2O melts?

Potential energy increases

Most kinetic energy is at the highest temperature.

True

Which of the following is an endothermic process?

Vaporization of water

The force that holds one water molecule adjacent water molecules is called

a hydrogen bond.

A substance that heats up relatively quickly has a

low specific heat capacity.

Fahrenheit and Celsius are two

temperature scales.

A phase diagram shows the relationship between

temperature, pressure, and the three phases of matter

The faster the particles of a gas are moving

the greater their energy and the higher their temperature.