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Chapter 1: Matter and Energy
Terms in this set (11)
What kinds of information are needed to formulate a hypothesis?
A hypothesis is a tentative explanation of observed phenomena or facts and is used as a basis for further testing. As such, the observations/phenomena/facts must be established before a hypothesis can be formulated
How does a hypothesis differ from a scientific theory?
A hypothesis is a tentative explanation of an observation or set of observations, whereas a scientific theory is a concise explanation of a natural phenomenon that has been extensively tested and explains why certain phenomena are always observed.
Notice that a hypothesis might become a theory after much experimental testing.
Is it possible to disprove a scientific hypothesis?
Yes, any experimental evidence that is not consistent with the hypothesis (a tentative explanation) disproves the validity of the hypothesis and the hypothesis must be modified or discarded in order to consistent with the experimental evidence.
Describe how a scientific theory differs from the meaning of theory as it is used in normal conversation?
Whereas theory in normal conversation usually means someone's idea or opinion that is open to speculation, a scientific theory on the other hand is a concise and testable explanation of natural phenomena based on extensive observation, experimentation and testing that can accurately predict the results of experiments. Theory in normal conversation is more akin to a hypothesis, a tentative possible explanation or a guess that may or may not be testable or correct
Can a theory be proven?
In science, a theory is the best (current) possible explanation that is extensively supported by experimentation and observations. A theory is normally considered nearly equivalent to fact in science, without being the absolute truth. Even a theory that has been sufficiently tested cannot be proven absolutely but does have many, many supporting experiments whose observations strongly support it. Even just one experiment however that is counter to the explanation for a phenomenon that the theory explains could disprove a theory, so theories may be toppled and replaced with new explanations and theories. So a theory can never be proven absolutely correct but they can be disproven.
With sufficient supporting evidence, can a scientific theory eventually become a scientific law?
No, a scientific theory can never become a scientific law because they are fundamentally different parts of the scientific method. A scientific theory is an extensively tested explanation of some observed natural phenomena. Further testing and additional supporting evidence makes it a better supported theory but does not make it a scientific law. A scientific law is not an explanation of observed natural phenomena but is a statement of basic scientific principles. Basically a scientific law attempts to state what happens while a scientific theory attempts to explain why it happens. For example, Boyle's Law states that the volume of a gas is inversely proportional to the pressure of the gas. Boyle's Law makes no attempt to explain the volume/pressure relationship of gasses. On the other hand the Kinetic Molecular Theory (KMT) of gasses does explain why the volule pressure relationship of gases exists.
Which of the following foods is a heterogeneous mixture?
(a) apple juice;
(b) cooking oil;
(c) solid butter;
(d) orange juice;
(e) tomato juice.
A heterogeneous mixture has visible regions of different composition. d & e
Which of the following is a homogeneous mixture?
(a) a bronze sword from ancient Greece;
(c) Nile River water;
(e) compressed air in a scuba tank.
b, d, e
Indicate whether each of the following properties is a physical or chemical property of sodium:
a. Its density is greater than that of kerosene and less than that of water.
b. It has a lower melting point than most metals.
c. It is an excellent conductor of heat and electricity.
d. It is soft and can be easily cut with a knife.
e. Freshly cut sodium is shiny, but it rapidly tarnishes in contact with air.
f. It reacts very vigorously with water, releasing hydrogen gas.
Physical properties are those that can be observed without transforming the substance into another substance. Chemical properties are observed only when one substance reacts with another and therefore is transformed into another substance. Density, melting point, thermal and electrical conductivity, and softness (a-d) are all physical properties, whereas tarnishing and reaction with water (e and f) are both chemical properties.
What occupies the space between the particles that make up a gas?
A gas consists of particles (atoms or molecules) that are far apart from each other and therfore there is nothing (no other atoms or molecules) exists in the space between particles in a gas. Because a gas consists of mostly empty space, most gases are highly compressible.
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