REVIEW QUESTIONS

Chapter 3

1. Classify the following properties of sodium metal as physical or chemical:
   a) silver metallic color
   b) turns grey in air
   c) melts at
   d) reacts explosively with chlorine
   e) dissolves in water to produce a gas
   f) malleable (can be shaped)
   

   

   
   
   chemical
   
   physical
   
   chemical
   
   chemical
   
   physical
2. Classify the following changes as physical or chemical :
   a) steam condenses to a liquid on a cool surface
   physical
   b) baking soda dissolves in vinegar, producing bubbles
   chemical
   c) moth balls gradually disappear at room temperature
   physical
   d) when a can of soda is opened bubbles form
   physical
3. Complete each statement below by choosing a suitable word or phrase:
   a) At the beach, sand is hotter than water in the day because it has a lower specific heat.
   b) Changes that do not involve a change in composition are called physical changes
   c) When water freezes to ice, energy is released
   d) For all substances, heat of fusion is lower than heat of vaporization. than heat of vaporization.
4. How many calories of heat are required to heat 45 g of water from to ? (Specific heat of water )

5. A sample of oxygen weighing 18 g was heated in presence of nitrogen and a chemical change occurred. The product was found to have a mass of 56 g . How much nitrogen reacted in this reaction?

6. A sample of gold weighing 15 g requires 84 calories of heat to increase its temperature from to . Calculate the specific heat of gold.

7. How much heat (in kcal) is required to melt a 20.0 lb bag of ice at ? (Heat of fusion of ice 80.0 cal.g)

8. When 2.0 kg of dry ice sublimes at its normal sublimation point, it absorbs 94 kcal of heat. Calculate the heat of sublimation for dry ice in .

9. How many calories of heat are required to heat 85.0 g of water at to steam at ? (Specific heat of water ; heat of vaporization of water )