Regents Chemistry Practice Problems : ENERGY AND HEAT

Heat always travels from an object with higher temperature to an object with lower temperature. A heat transfer would occur from the cup to the hand. Choice 4

All of the heat equations can be found on Table T in the Reference Table. Melting is a phase change where the substance changes from solid to liquid. An equation to calculate heat absorbed during melting is q = mHf where q=heat and Hf =heat of fusion. Mass is 26.2 grams according to the given. Heat of fusion of water can be found in Table B and is 334 J/g. Now, we can plug everything in q= 26.2 g*334 J/g = 8750.8 J
Choice 1

In a Cooling Curve, the lines that are horizontal, such as the line from 2 minutes to 6 minutes, represent a decrease in the potential energy and no change in the kinetic energy. Temperature is the measure of the average kinetic energy. Since from 2minutes to 4 minutes, temperature is not changing, the average kinetic energy will not change either. Choice 4

According to Table A on the Reference Table, 0°C is equal to 273K. To covert between Celsius and Kelvin we can use the following equation, °C+273 = K. Let’s plug in the value given,
°C+273 =35 K
°C = -238°C
Choice 1

Heat always flows from the object at higher temperature to the object with lower temperature. We are looking for a temperature less than 20°C, which is choice 1.

All of the heat equations can be found on Table T in the Reference Table. An equation that involves specific heat capacity is q=mCΔT where q=heat m = mass and C = specific heat capacity.
m=40.0 grams
C = 4.18 J/g•K (Table B on the Reference Table gives specific heat capacity of water)
ΔT = Tfinal – Tinitial = 30.0°C-10.0°C = 20.0°C
q=40.0 grams*4.18 J/g•K *20.0°C = 3344J

Answer:2

Temperature is the measure of the average kinetic energy. The question asks for sample with the lowest average kinetic energy. We need to find a sample with the lowest temperature, which is choice 1

All of the heat equations can be found on Table T on the Reference Table. Melting is a phase change where the substance changes from solid to liquid. An equation to calculate heat absorbed during melting is q = mHf where q=heat and Hf =heat of fusion. Mass is 43 grams according to the given. Heat of fusion is 1.9*10³J/g. Now, we can plug everything in q= 43g*1.9*10³ J/g = 81700J
Choice 3

All of the heat equations can be found on Table T in the Reference Table. An equation that involves specific heat capacity is q=mCΔT where q=heat m = mass and C = specific heat capacity.
m=24 grams
C = 0.90J/gK
ΔT = Tfinal – Tinitial = 350.K-300.K = 50K
q=24 grams*0.90J/gK *50K = 1080K

Answer:3