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CK-12 Chemistry - Basic
Answer Key
Chapter 4: Introduction to Chemistry
.1 Evolution of the Atomic Model
Check Your Understanding
1. What are the general properties of matter?
Answer: Matter can be described in terms of its physical characteristics as well as its
chemical characteristics. For instance, the physical characteristics of liquid water are
that it has a density of 1 g/mL. Many substances will dissolve readily in water – another
physical characteristic.
2. We widely accept that all matter is comprised of similar kinds of particles that are too
small to detect with the unaided eye. For example, we know that when a candle burns it
gives off carbon dioxide and water vapor. Yet we cannot actually “see” these gases.
How can we study something we cannot directly see, but know exists? Can you give an
example?
Answer: Even though we cannot readily see the carbon dioxide and water vapor
produced, we could measure the mass changes in the candle. This would indirectly tell
us how much gas was produced. We could also place a plate of glass over the burning
candle to condense the water vapor which would then be visible in its liquid form.
Chemistry depends on indirect measurement quite frequently to make sense and
describe the chemical world.
Review Questions
Questions:
1. Compare and contrast the continuous theory of matter with the discontinuous theory
of matter.
2. Which of the following did Proust discover?
a. Elements combine in unpredictable ratios with other elements.
b. The mass of an element is always changing even when combined with
another element.
c. Chemical compounds always contain the same proportion of elements by
mass, regardless of amount
