Chemistry I: Matter & Energy Review
Define the following terms:
1. Energy - The capacity to do work or produce light
2. Kinetic energy – Energy of Motion
3. Potential energy – Stored energy of position
4. Exothermic – Release of heat
5. Endothermic – Absorption of heat
6. Conservation - The fact that mass and energy cannot be created or destroyed
7. Temperature – Average kinetic energy of the molecules
8. Hypothesis – An assertion subject to verification or proof as a premise from which a conclusion is
drawn
9. Variable - A factor that could affect the results of an experiment
10. Theory - A well-tested explanation of observations
11. Law - statement or mathematical expression that reliably describes a behavior of the natural
world
12. Conclusion - A proposed explanation of observations
13. Conservation of mass – The fact that matter cannot be destroyed in a chemical reaction
14. Precision – The closeness of a measurement to other measurements
15. Accuracy – The closeness of a measurement to the true value
16. Chemistry – The study of matter and changes that occur in matter
17. Chemical property – A characteristic of a substance that cannot be observed without chemically
changing the identity of the substance
18. Physical property – A characteristic of a substance that can be observed without changing the
identity of the substance
19. Chemical change – A change in which one or more new products with new properties is produced
20. Physical change – A change in which the same substance remains before and after the change
21. Solid – State of matter that has both a definite shape and volume
22. Liquid – State of matter that has a definite volume but no definite shape
23. Gas – State of matter with no definite shape or volume
24. Homogeneous – Uniform
25. Heterogeneous – Not uniform
26. Quantitative – A measurement that involves a number
27. Qualitative – A measurement that describes a characteristic of a substance that is not a number
Short Answer:
Describe the energy change involved when an egg cooks.
Energy is absorbed by the raw egg. The absorbed energy is stored as chemical energy in the cooked egg.
Explain the difference in an endothermic process and an exothermic process.
An endothermic process absorbs energy, and an exothermic process releases energy
Explain how energy is conserved when a piece of paper burns.
The total energy contained in the bonds of the paper and oxygen equals the total energy contained in the
bonds of the ashes and gases produced and the heat energy released
Use pouring hot chocolate into a cold cup to explain the difference in heat and temperature.
The hot chocolate has a higher average kinetic energy of its particles because it has a higher temperature.
The energy that is transferred from the particles in the hot chocolate to the particles of the cup is heat
Explain how to change from Kelvin to degrees Celsius.
Kelvin units are the same size as degrees Celsius. The zero point on the Kelvin scale is 273 units below
that on the Celsius scale, so to change from Kelvin to degrees Celsius, subtract 273 from the Kelvin
temperature
Why should a scientist record all observations, even those that appear insignificant?
Many important discoveries are made through mistakes or by accident. If seemingly insignificant
observations are not recorded, such discoveries cannot be reproduced
What are the first steps scientists take to analyze the cause of a disease?
Scientists must first observe the symptoms of the disease. Then they form a hypothesis and design an
experiment with a control and variables to test their hypothesis about the probable cause of the disease
Explain what is meant by a scientific method.
A scientific method is a logical, systematic approach to problem solving. The exact steps followed might
vary from problem to problem
What is the purpose of a control in an experiment?
Answers might include that controls eliminate error due to unforeseen variations in the system, serve as a
comparison or baseline for other data, and increase confidence in collected data
Explain why pictures of atoms and molecules are models.
The pictures represent the atoms and molecules and are consistent with what we know about their
behavior. They are not true representations because atoms and molecules are not hard, colored sphere
Differentiate between a theory and a law.
A theory is a broad generalization based on observations, data, and reasoning, that is used to explain a
phenomenon. A law is a mathematical expression or statement that describes the behavior of some part of
the natural world
The mass of a 3.45-g piece of aluminum was measured several times. The measured masses were
2.67 g, 2.59 g, 2.60 g, and 2.64 g. Use these results to explain the difference between accuracy
and precision.
Because the masses were close to each other, they were precise. Because they were not close to the
accepted value of the mass, they were not accurate
The specific heat of iron is 0.449 J/(g K), and that of aluminum is 0.897 J/(g K). Explain how
you know which metal will absorb and release more energy under the same temperature change.
Assume samples of equal mass.
Because the specific heat of aluminum is greater than that of iron, aluminum will absorb and release more
energy
Explain why the number 62.605 x 106 is not in correct scientific notation. What is the correct
scientific notation for this number?
The first part of the number should be a number between one and ten. The correct form is 6.2605  107
A 10.0 g sample of cadmium absorbed 43 J of energy as it was heated. The initial temperature
was 285 K. What was the final temperature of the metal if the specific heat of cadmium
is 0.232 J/(g K)?
final temperature = initial temperature + T = 285 K + 14 K = 299 K
The specific heat of tin is 0.228 J/(g K). A sample of tin absorbs 92 J as it is heated
from 271 K to 295 K. What is the mass of the sample?
The specific heat of carbon is 0.709 J/(g K). How much energy is absorbed if a 7.34 g sample is
heated until its temperature increases by 12 K?
q = T m  cp= 12 K  7.34 g 0.709 J/(g K) = 62 J
If a 12.6 g sample of a material is heated from 181 K to 199 K, 46 J of energy is absorbed. What
is the specific heat of the material?
When water boils, steam forms. When vinegar and baking soda combine, carbon dioxide gas is
released. Which change is physical, and which is chemical? How do you know?
In both changes, a gas is produced. However, water boiling is a physical change because no new products
are produced; steam is still water. In the chemical change, a new product–carbon dioxide–is formed
State which one of the following observations is quantitative and explain why it is.
a. The liquid turns blue litmus paper red.
b. The liquid boils at 100°C.
c. The liquid tastes bitter.
d. The liquid is cloudy.
Answer b is quantitative because it involves a measured quantity. The other choices involve properties
that are not quantitatively measured
Explain the difference between a pure substance and a homogeneous mixture. Use an example in
your explanation
A homogeneous mixture can be separated by physical means, whereas a pure substance cannot. For
example, salt can be removed from a salt-water mixture by evaporating the water, but to separate water
into hydrogen and oxygen requires chemical means
Name three different ways that mixtures can be separated.
Any logical physical means of separation can be accepted. Answers might include filtration, distillation,
decanting, sorting, evaporation, or use of a sieve