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)
2. Classify the following changes as physical or chemical :
   a) steam condenses to a liquid on a cool surface
   b) baking soda dissolves in vinegar, producing bubbles
   c) moth balls gradually disappear at room temperature
   d) when a can of soda is opened bubbles form
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 (higher/lower) specific heat.
   b) Changes that do not involve a change in composition are called (physical/chemical) changes,
   c) When water freezes to ice, energy is (absorbed/released)
   d) For all substances, heat of fusion is (lower/greater) 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 )
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 cal/g.
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 )