ET 27 Review Questions

For the formula:
 Q= m c ∆T
The  units for specific heat are:

• g /J C
• °C/g J
• kJ/g
• J/g°C

If two objects have different temperatures when they come in contact, heat will flow from the warmer object to the cooler one UNTIL ____________

• one reaches a temperature of zero

• they both have an equal temperature

• one runs out of energy

If the specific heat of water is 4.18 J/g∙°C, how much heat is required to increase the temperature of 1.2 kg of water from 23 °C to 39 °C? (show your work)

• -80,256 J

• 80.256 J

• 80,256 J

• -80.256 J

What is the specific heat of an unknown substance if 100.0 g of it at 200.0 °C reaches an equilibrium temperature of 27.1 °C when it comes in contact with a calorimeter of water.  The water weighs 75. g and had an initial temperature of 20.00 °C?  (Specific heat of water is 4.18 J/g°C) (show your work)

• 0.111 J/g°C
• 1.29 J/g°C
• 0.129 J/g°C
• 22225.85 J

For a skillet, used for cooking, do you want a high or low specific heat

• High, so that it will need more energy to heat up

• Low, so that it will change temperature quickly

A sample of iron receives 50.J of heat energy that raises the temperature of the iron by 25.0°C. If iron has a specific heat of 0.10 J/g°C, what is the mass of the iron sample?  (show your work)

• 25g
• 30g
• 20g
• 50g

A reaction is performed in a beaker with a temperature probe recording the temperature changes of the reaction.  If the temperature began at 15.0 degrees Celsius and ended at 27.5 degrees Celsius. Is the reaction endothermic or exothermic?

• Exothermic
• Endothermic

Calorimetry Question:
A piece of metal with a mass of 32.8 g is heated to 100.5°C and dropped into 138.2 g of water at 20.0°C.  The final temperature of the system is 30.2°C.  What is the specific heat capacity of the metal? (show your work)

• 2.56 J/g°C
• 0.391 J/g°C
• 5.29 J/g°C
• 3.50 J/g°C

What is a tool that measures the heat of chemical reactions?

• calorimeter
•  calorie
• Styrofoam™ cup
• none of these

Calorimeters use insulating materials to:

• encourage affordable materials in science experiments in schools.
• preserve the heat of the environment outside the Styrofoam cup.
• prevent heat from escaping to the environment.
• keep the liquid inside the Styrofoam cup from overheating.