Phases and Phase Changes-Chemistry Chapter 5
A student performing a chemistry lab is required to heat 400 grams of ice held at -50 °C in a container until it reached a certain temperature in the liquid phase. The student was told to transfer exactly 250 kJ of heat into the container while recording the temperature. Which of the following values is approximately the final temperature recorded? Ice has a specific heat of 2.108 J/g°C. Liquid H2O has a specific heat of 4.186 J/g°C. The heat of fusion of water is 0.334 kJ/g. The heat of vaporization of water is 2.26 kJ/g.
44 C
Which of the following best represents the phase diagram of water? (READ)
The phase diagram for water has a solid/liquid boundary that slants up and to the left. Water is unique because it is denser in the liquid phase than the solid phase. This is why ice can float on water. This also means that it is possible to melt a piece of ice by only raising pressure and not temperature.
The figure below depicts the heating curve of H2O. Solid H2O has a specific heat of 2.108 J/g°C. Liquid H2O has a specific heat of 4.186 J/g°C. The heat of fusion of water is 0.334 kJ/g. The heat of vaporization of water is 2.26 kJ/g. What is the minimum amount of heat necessary to transition 100 g of water from point A to point B?
3.1 x 10^5 J
heat of fusion heat of vaporization at phase changes:
Amount of energy required to change a substance from the solid phase to the liquid phase. The amount of energy required for the liquid at its boiling point to become a gas temp remains constant while heat is being added
Amorphous solids Crystalline solids Ionic solids Molecular solids Network solids Metallic solids
Does not have order. Highly ordered in a repeating pattern. Ordered to optimize electrostatic interactions. Held together by intermolecular attractions. Have high melting points due to intricate covalent bonding. Have superior electrical conductivity properties due to free floating valence electrons.
Shown below is the general phase diagram for most substances. Match each term with its corresponding point on the graph Triple Critical Superficial
E H G
Condensation Freezing Sublimation(Skips intermediate) Deposition fusion (melting) Vaporization
Gas to liquid liquid to solid solid to gas gas to solid solid to liquid Liquid to gas
Solid Liquid Gas
Hard to compress; set volume and shape No set shape; set volume Compressible; no set shape or set volume
Shown below is the phase diagram for substance Y. What could happen to substance Y if it were placed under conditions of increased pressure and temperature?
Substance Y can undergo condensation. -Increasing pressure and temperature can shift substance Y from C to B. In a generic phase diagram, C represents the gas phase and B represents the liquid phase. A shift from the gas to liquid phase is known as condensation.
Shown below is the general phase diagram for most substances. Match the letters with its corresponding definitions. D E F
The phase in which a substance exhibits properties of a gas and a liquid. Any increase in temperature or pressure past this point will cause the substance to become indistinguishable between liquid and gaseous states. At this point, the substance exists as a combination of gas, liquid, and solid.
Capillary action results from the adhesive forces between the water and the container. (READ) Which of the following correctly pairs the SI unit for pressure with its units?
This occurs when adhesive forces are greater than cohesive forces. Adhesion refers to attraction between water and the container. Cohesion refers to attraction between the various water molecules. The SI unit for pressure is the pascal and is given in N/m2.
Which of the following statements below does accurately describe crystalline solids? Ionic Solid Molecular Solids Covalent networks solids Metallic Bonding
consists of cations and anions that are held together by electrostatic interactions are held together by intermolecular forces such as diamonds have a high melting point due to intricate bonding between atoms are surrounded be delocalized valence electrons
Shown below is a single component phase diagram for substance X. Which of the following conditions could result in substance X undergoing sublimation? Select all that apply.
decrease pressure -Sublimation is the process in which a substance transitions from the solid phase directly into the gas phase. Decreasing pressure moves the dot down, which can result in a transition into the gas phase. increased temp -Sublimation is the process in which a substance transitions from the solid phase directly into the gas phase. Increasing temperature moves the dot to the right, which can result in a transition into the gas phase.
Q=mc∆T
q= heat flow kJ m= mass kg c= specific heat kJ/kg·K ∆T= change in temp K
Viscosity Surface tension (READ)
resistance of liquid to flow ex. molasses amount of energy needed to increase the surface area of the liquid (stronger, more energetically favorable), tension created at the liquid's surface by the intermolecular forces between molecules,
G<0 G>0 Increase in entropy Increase in enthalpy
spontaneous non spontaneous thermodynamically favorable +H,+S=-G requires heat thermodynamically unfavorable G+
