Chemistry exam
Which of the following is a synthesis reaction?
BaO + CO2 → BaCO3
Which of the following shows a valid combustion reaction?
C2H4 + 3O2 → 2CO2 + 2H2O
What best explains the type of energy present in the vibrating atoms of a substance?
It is thermal energy, which is a type of kinetic energy.
Which of the following describes the characteristics of a solid?
Particles are packed closely together in an organized way and maintain their set shape and volume.
Valence electrons are involved in chemical bonding.
true
What is true of synthesis and decomposition reactions?
Synthesis reactions are the opposite of decomposition reactions.
What volume is equivalent to 0.0015 m3?
1.5 x 106 mm3
0.32 L is equal to ____ mL. (Only input whole number answer
320
A synthesis reaction can be identified because it only has pure elements on the left side of the arrow and compounds on the right side of the arrow.
false
An ordered list of chemical substances is shown. Chemical Substances 1 CuO 2 O2 3 Cu2O 4 N2 5 C2H5NH2 6 Li2O Which substances in the list can be some of the reactants and products in the same combustion reaction?
2, 4, and 5
Which of the following pairs of substances would best be separated using a centrifuge, and why?
Cream and milk, because of their difference in density
An atom's Lewis dot structure has two dots. Which of the following elements could it be, and why?
Magnesium, because it is a group 2 element with two valence electrons.
Which type of electromagnetic radiation has a shorter wavelength than blue light?
X-rays
If a crate contains 25,500 ounces (oz) of rice, about how many kilograms (kg) does it contain? (3 points) (1 lb = 16 oz, 1 lb = 0.454 kg)
724
When heat energy is added, two changes are observed: Change A: Solid changes to a liquid.Change B: Solid changes directly to a gas. What are the names for phase changes A and B?
A is melting and B is sublimation.
Yasir wants to determine if there is a relationship between room color and sleep. Based on his research, Yasir makes an educated guess that people fall asleep more quickly in a room painted blue than in a room painted yellow. He asks several people which color they like better—yellow or blue—and uses their responses to determine if his educated guess was correct. What is missing from Yasir's scientific investigation?
An experiment that directly tests the hypothesis
An unbalanced chemical equation is shown: 2CaO + 2H2O → Ca(OH)2 Which of the following statements explains why the equation is not balanced? (4 points) Select one: a. Four molecules of Ca(OH)2 should be produced during the decomposition reaction. b. Two molecules of Ca(OH)2 should be produced during the decomposition reaction. c. Four molecules of Ca(OH)2 should be produced during the synthesis reaction. d. Two molecules of Ca(OH)2 should be produced during the synthesis reaction.
Two molecules of Ca(OH)2 should be produced during the synthesis reaction.
Which of the following could be considered a scientific statement?
X−rays have a lower frequency than microwaves.
All combustion reactions have oxygen as a reactant.
true
Which of the following is a physical property?
solubility
Which of the following is a valid conversion factor?
1000ml/1l
What type of mixture is chicken noodle soup?
A heterogeneous mixture, because the different components are mixed unevenly within the substance
The amount of stored chemical energy is what determines the temperature of a substance.
False
What does a decrease in temperature indicate about the molecules in a sample of liquid water?
Increased kinetic energy of the molecules
During an experiment a thermometer was placed in a beaker containing hydrogen peroxide. The following observations were recorded when yeast granules were added to hydrogen peroxide. Observation 1: Fizzing and bubbling took place.Observation 2: The temperature began to rise. Based on the observation, justify the type of change (physical or chemical) that took place.
Observation 1 is a type of chemical change because it was fizzing and bubbling. Observation 2 is a type of physical change because of the temperature rising.
Which of the following is an example of a chemical change?
Rusting iron
How does a sample of helium at 15 °C compare to a sample of helium at 215 K?
The helium at 15 °C has a higher average kinetic energy than the sample at 215 K.
When placed in a freezer, liquid water turns into solid ice. What best describes this change?
The water molecules slow down, bonds are broken, and the separated atoms spread out.
Electrons have been shown to have both wavelike and particle-like properties.
true
If a question is asking about an opinion, it can be answered with science.
False
Which of the following is a sign a chemical reaction has occurred?
A liquid forms bubbles when heated.
A scientist hypothesizes that the temperature at which a turtle's egg is incubated determines the sex of the offspring (whether it will be male or female). What is the independent variable?
Temperature
The kilogram is the SI unit for mass.
True
Which of the following correctly describes a compound?
The atoms can only combine in fixed ratios, and they can only be separated by a chemical change.
Four properties of water are listed. It reacts with halogens to form oxygen gas as one of the products. It is transparent and tasteless in its pure form. It freezes at a temperature of 0 °C and lower. It decomposes to form hydrogen and oxygen. Which are the chemical properties of water?
1 and 4
A tank has 30 gallons of gasoline. How many liters of gasoline are there in the tank? (3 points) Use 1 gallon = 3.8 liters
114 liters
If a liquid has a density of 1,200 g/L, what is its density in cg/mL?
120 cg/mL
Which chemical equation correctly represents the reaction that takes place when nitrogen gas and hydrogen gas are formed as ammonia decomposes?
2NH3(g) → N2(g) + 3H2(g)
What is the frequency of a wave with a wavelength of 6.40 x 104 meters?
4.69 x 103 Hz
An atom has the following electron configuration. 1s22s22p63s23p3 How many valence electrons does this atom have?
5
Why is the reaction between potassium (K) and chlorine (Cl) considered an oxidation-reduction reaction? (4 points) K(s) + Cl2(g) → 2KCl(s)
Chlorine takes electrons from potassium in the reaction.
What part of the scientific method involves constructing a tentative and testable explanation based on observations and research?
Constructing a hypothesis
Mass is an intensive physical property because it is dependent on the size of the sample.
False
Steel is an example of a pure substance because it is made up of two different metals melted together.
False
Which of the following cannot be tested by science? (2 points) Select one: a. How adrenaline affects the mating behaviors of animals b. How emotion affects the quality of a painting c. How gravity affects the movement of an object d. How temperature affects the sex of offspring
How emotion affects the quality of a painting
Which of the following is true of science?
It is based on testable and replicable evidence.
What is generally true about the compressibility of solids?
It is lower than the compressibility of plasmas and gases.
Using the measurements in the table, determine which unidentified metal has the lowest density. MetalVolumeMassA12.5 cm3122 gB14.2 cm3132 gC18.1 cm3129 gD12.7 cm3126 g
Metal A
Read the two questions. Question 1: Should acid precipitation be a concern for the new age environmentalist?Question 2: Does acid precipitation in forests affect the reproduction rate in birds? Use complete sentences to explain whether both questions can be answered by science or not. Be sure to explain why for each question.
Question 1 asks if acid precipitation should be a concern for the new age environmentalist. This question can not be answered by science because it would be answered as an opinion or a moral value. Question 2 asks if acid precipitation in forests affect the reproduction rate in birds. This question can be answered in science because it would be tested to answer the question.
What energy transfer occurs when a solar panel uses sunlight to provide power to a house?
Radiant energy is converted to electrical energy.
A student describes the motion of particles in each of the four different states of matter. State 1: Particles that are charged move freelyState 2: Particles move freely at high speedState 3: Particles are locked in placeState 4: Particles slide past one another Which state describes solids?
State 3
During an experiment, it is observed that iron powder sinks in water and sulfur powder floats in water. What will most likely be observed when sulfur powder and iron powder are mixed together and then added to water?
Sulfur will float and iron will sink because each will retain its properties.
Which of the following would be a warning sign that information about a weight loss medication is not reliable science? a. The investigation compared a group that took the medication to a control group that did not take the medication. b. The scientists and all test subjects involved in the investigation work for the company that sells the medication. c. The weight loss medication worked for 95 out of the 100 test subjects, while only 15 of the 100 control subjects lost weight. d. The weight loss results were replicated by scientists conducting a study at an independent institution.
The scientists and all test subjects involved in the investigation work for the company that sells the medication.
The electron configuration of an element is 1s22s22p6. Describe what most likely happens when an atom of this element comes near an atom having seven valence electrons.
They would not react because the element 1s22s22p6 had 6 valence electrons and would need 2 more valence electrons to complete the valence shell. Whereas, the atom having seven valence electrons would only need 1 more valence electron to complete the valence shell.
What is kinetic energy?
energy of motion
Compared to ultraviolet light, an electromagnetic wave that has a higher frequency will also have ________.
shorter wavelength and equal speed
The reaction CO2(g) → C(s) + O2(g) is a decomposition reaction.
true