8th Grade Physical Science Chapter 2 Review
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Which of the following is an example of a chemical change
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A piece of glass breaking
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An apple turning brown
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Folding a piece of paper
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Cutting an orange in half
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This 8th grade physical science review assesses key concepts in thermal conductivity, chemical reactions, density, and properties of substances. It enhances understanding of how these properties influence practical applications, critical for foundational science education.
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- 2.
Which of the substances is MOST soluble in water?
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Wood
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Salt
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Sand
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Iron
Correct Answer
A. SaltExplanation
Salt is the most soluble substance in water because it is an ionic compound composed of positive and negative ions. When salt is added to water, the water molecules surround the ions and pull them apart, dissolving the salt. This process is known as hydration. The strong attraction between the ions and the polar water molecules allows for a high degree of solubility, making salt dissolve easily in water. In contrast, wood, sand, and iron are not soluble in water as they are not composed of ions and do not have the same polar properties.Rate this question:
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- 3.
What is the term used to describe the temperature at which a solid becomes a liquid
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Sublimation point
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Melting point
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Condensing point
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Boiling point
Correct Answer
A. Melting pointExplanation
The term used to describe the temperature at which a solid becomes a liquid is the melting point.Rate this question:
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- 4.
A student divides several objects into two groups based on their ability to float in water. Which property is the student using to classify the objects?
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Mass
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Density
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Weight
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Phase
Correct Answer
A. DensityExplanation
The student is using density to classify the objects. Density is the measure of how much mass is contained within a given volume. Objects with higher density will sink in water, while objects with lower density will float. Therefore, by dividing the objects into two groups based on their ability to float in water, the student is essentially classifying them based on their density.Rate this question:
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- 5.
Cutting a piece of paper, crushing salt into smaller pieces, and a pencil being sharpened are all examples of what
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Chemical changes
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Chemical properties
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Physical changes
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Physical properties
Correct Answer
A. Physical changesExplanation
Cutting a piece of paper, crushing salt into smaller pieces, and sharpening a pencil are all examples of physical changes. In these processes, the substances undergo a change in their physical appearance or form, but their chemical composition remains the same. The paper is still made of cellulose, the salt is still composed of sodium and chlorine ions, and the pencil is still made of graphite. Therefore, these changes are classified as physical changes rather than chemical changes, which involve a rearrangement of atoms and a formation of new substances.Rate this question:
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- 6.
Which of the following is a chemical property of a substance
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Mass of 372 g
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Reacts with HCI
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Density of 37 g/cm (squared)
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White powder with silver specks
Correct Answer
A. Reacts with HCIExplanation
The correct answer is "reacts with HCI." This is a chemical property because it describes how the substance reacts with another substance, in this case, hydrochloric acid (HCI). Chemical properties relate to the substance's ability to undergo chemical reactions and change its composition. In this case, the substance shows a chemical reaction with HCI, indicating its reactivity and providing information about its chemical behavior.Rate this question:
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- 7.
A raw egg will float in concentrated salt water but sink in tap water. What can a person conclude from this observation
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A raw egg has the same density as salt water
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A raw egg, salt water, and tap water have the same density
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A raw egg is less dense than salt water but more dense than tap water
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A raw egg is less dense than tap water but more dense than salt water
Correct Answer
A. A raw egg is less dense than salt water but more dense than tap waterExplanation
A raw egg will float in concentrated salt water but sink in tap water because the density of the egg is less than that of the salt water but more than that of the tap water.Rate this question:
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- 8.
The ability of an object to transfer heat is known as thermal conductivity. Which of the following types of elements has the most efficient thermal conductivity?
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Semimetals
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Metals
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Nonmetals
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Gases
Correct Answer
A. MetalsExplanation
Metals have the most efficient thermal conductivity compared to semimetals, nonmetals, and gases. This is because metals have a large number of free electrons that can easily move and transfer heat energy through the material. These free electrons can rapidly carry and distribute heat, making metals excellent conductors of heat. In contrast, semimetals, nonmetals, and gases have fewer free electrons or lack the necessary atomic structure to efficiently transfer heat, resulting in lower thermal conductivity.Rate this question:
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- 9.
Which part of digestion is mainly a chemical change
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Teeth break food into smaller pieces
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Throat muscles push food toward the stomach
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Stomach acids dissolve food into nutrients
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Intestinal cells transport nutrients into the blood
Correct Answer
A. Stomach acids dissolve food into nutrientsExplanation
The stomach acids play a crucial role in digestion by breaking down the food into nutrients. These acids, such as hydrochloric acid, help to dissolve the food particles and break them down into smaller molecules. This process is mainly a chemical change as it involves the breakdown of complex molecules into simpler ones through chemical reactions. Once the food is broken down into nutrients, it can be easily absorbed by the body for energy and other essential functions.Rate this question:
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- 10.
The process of digestion breaks down proteins into smaller molecules that are used to rebuild other proteins. During digestion, proteins undergo
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Cell division
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Nuclear reactions
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Natural selection
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Chemical changes
Correct Answer
A. Chemical changesExplanation
During the process of digestion, proteins are broken down into smaller molecules through chemical changes. This involves the action of enzymes, such as proteases, which break the peptide bonds between amino acids in proteins. These smaller molecules, such as amino acids, can then be absorbed by the body and used for various purposes, including the synthesis of new proteins. Cell division, nuclear reactions, and natural selection are not directly involved in the process of protein digestion.Rate this question:
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- 11.
Which of the following is an example of a chemical property of matter
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Reaction with another element
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Density of an element
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Color of an element
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Freezing point of element
Correct Answer
A. Reaction with another elementExplanation
The ability of a substance to undergo a chemical reaction with another element is an example of a chemical property of matter. Chemical properties describe how a substance interacts with other substances to form new substances. In this case, the substance's reaction with another element indicates its chemical reactivity and ability to form new compounds.Rate this question:
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- 12.
ORIGINAL MATERIALEVENTCHANGEpiece of ironleft outdoors in the rainrust formsstack of fire woodused in fireplacebecomes smoke and ashescopper pennyplaced in vinegargas bubbles formThe chart shows how materials can change chemically.Why are these changes classified as chemical changes?
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New substances are formed
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Materials take different shapes
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Temperature affects the object
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Some energy is absorbed
Correct Answer
A. New substances are formedExplanation
These changes are classified as chemical changes because new substances are formed. In each of the given examples, the original material undergoes a chemical reaction and transforms into a different substance. The iron reacts with the oxygen and moisture in the air to form rust. The firewood undergoes combustion and is converted into smoke and ashes. The copper penny reacts with the vinegar to form gas bubbles. In all of these cases, the composition of the original material changes, resulting in the formation of new substances.Rate this question:
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- 13.
A student placed a small chip of limestone into a hydrochloric acid solution, and carbon dioxide gas was released. The carbon dioxide provided evidence that
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Only a physical change has occurred
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A chemical change has occurred
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Only a loss of mass has occurred
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The formation of an element has occurred
Correct Answer
A. A chemical change has occurredExplanation
When the chip of limestone is placed in hydrochloric acid solution, a chemical reaction occurs. The hydrochloric acid reacts with the limestone, causing it to break down and release carbon dioxide gas. This release of gas is evidence that a chemical change has occurred, as the reactants (limestone and hydrochloric acid) have been transformed into new substances (carbon dioxide gas and other compounds). This is different from a physical change, where the substance may change form or state but the chemical composition remains the same.Rate this question:
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- 14.
To calculate the density of an apple, one must know the ______________ and _______________ of the apple
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Height, volume
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Mass, volume
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Mass, weight
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Height, weight
Correct Answer
A. Mass, volumeExplanation
To calculate the density of an apple, one must know the mass and volume of the apple. Density is defined as the mass of an object divided by its volume. In this case, the mass of the apple and its volume are required to determine its density. The mass refers to the amount of matter in the apple, while the volume represents the space occupied by the apple. By dividing the mass by the volume, the density of the apple can be calculated.Rate this question:
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- 15.
Which of the following is NOT laboratory of a chemical reaction
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Large chunks of sodium chloride are placed in a mortar and pestle. The sodium chloride is broken into smaller pieces
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Hydrochloric acid is poured in a test tube containing a piece of magnesium. Bubbles of gas form.
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A solution of silver nitrate is added to a solution of sodium chloride. A solid white substance forms.
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A solution of sodium sulfide is added to hydrologic acid. A rotten smell is given off
Correct Answer
A. Large chunks of sodium chloride are placed in a mortar and pestle. The sodium chloride is broken into smaller piecesExplanation
The given answer is correct because it describes a physical change rather than a chemical reaction. Breaking sodium chloride into smaller pieces does not involve any chemical reactions or the formation of new substances. It is simply a change in the physical state of the substance.Rate this question:
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- 16.
During photosynthesis, carbon dioxide and water combine according to the general equation: Carbon dioxide+water : energy------------> sugar+oxygenWhy is photosynthesis a chemical reaction
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Because new substances are formed
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Because an input on energy is required
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Because the reactants are compounds
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Because the products include an element
Correct Answer
A. Because new substances are formedExplanation
Photosynthesis is a chemical reaction because new substances are formed. In this process, carbon dioxide and water react to produce sugar and oxygen. The reactants (carbon dioxide and water) combine and undergo a chemical change to form the products (sugar and oxygen). This transformation results in the formation of new substances, which is a characteristic of a chemical reaction.Rate this question:
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- 17.
Which fact about water is an example of a chemical property
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Water expands when it freezes
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The boiling point of water is 100 degrees C
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Water can separate into hydrogen and oxygen
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The density of water is greater than the density of ice
Correct Answer
A. Water can separate into hydrogen and oxygenExplanation
The fact that water can separate into hydrogen and oxygen is an example of a chemical property because it involves a chemical reaction. When water undergoes electrolysis, it breaks down into its constituent elements, hydrogen and oxygen. This process requires a chemical change and is not simply a physical change like freezing or boiling. Chemical properties describe the behavior of substances in terms of their ability to undergo chemical reactions and form new substances.Rate this question:
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- 18.
Water has a density of 1 g/mL. Which object will float in water?
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An object that has a density of 1.2 g/mL
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An object that has a density of 10 g/mL
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An object that has a density of 0.1 m/mL
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An object that has a density of 100 m/mL
Correct Answer
A. An object that has a density of 0.1 m/mLExplanation
Because the object must be less dense than the water to float in itRate this question:
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- 19.
Experimentdescription1Student blows through a straw into his milk carton; bubbles are produced 2Student blows through a straw into a beaker of limewater; bubbles are produced and the liquid becomes cloudy; small, white solid particles appearThe table above describes two experiments What can the student conclude about the experiments?
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Experiment 1 shows a physical change because the temperature changed
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Experiment 1 shows a chemical change because bubbles were produced
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Experiment 2 shows a physical change because its color changed
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Experiment 2 shows a chemical change because a new substance was produced
Correct Answer
A. Experiment 2 shows a chemical change because a new substance was producedExplanation
Experiment 2 shows a chemical change because a new substance was produced. This can be inferred from the fact that bubbles were produced, the liquid became cloudy, and small, white solid particles appeared. These observations suggest a chemical reaction occurred, resulting in the formation of a new substance. In contrast, Experiment 1 only resulted in the production of bubbles, which is indicative of a physical change rather than a chemical change.Rate this question:
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- 20.
Which is a physical change
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A piece of wood burning
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A copper roof changing colors
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Rust forming on an iron fence
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A sheet of paper shredding
Correct Answer
A. A sheet of paper shreddingExplanation
A physical change refers to a change in the physical properties of a substance without altering its chemical composition. Shredding a sheet of paper is a physical change because it only changes the size and shape of the paper, but the paper itself remains the same substance. Burning wood, changing colors of a copper roof, and rust forming on an iron fence are all chemical changes as they involve a transformation in the chemical composition of the materials involved.Rate this question:
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- 21.
Before the onset of a snowstorm, people spread salt on roads and sidewalks. Which property of salt explains this behavior?
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Salt decreases the combustion rate of water
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Salt decreases the freezing point of water
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Salt increases the freezing rate of water
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Salt increases the reactivity of water
Correct Answer
A. Salt decreases the freezing point of waterExplanation
Salt decreases the freezing point of water because it lowers the temperature at which water molecules can bond together and form ice. This is why salt is commonly used to melt ice on roads and sidewalks before a snowstorm. By lowering the freezing point, the salt prevents the water from freezing and forming dangerous ice patches, making it easier and safer for people to walk or drive on the surfaces.Rate this question:
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- 22.
A scientist placed a sample of lithium into a container of water. The scientist observed the lithium floating and making a buzzing sound as gas bubbles were forming around it. Which conclusion is BEST supported by this observation
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A chemical change took place
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The lithium was dissolved by the water
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Dissolved gases were released
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Water was vaporized
Correct Answer
A. A chemical change took placeExplanation
The observation of the lithium floating and making a buzzing sound as gas bubbles were forming around it indicates that a chemical change took place. This is because the formation of gas bubbles suggests a chemical reaction between the lithium and water, resulting in the release of gas. The floating and buzzing sound can also be attributed to the chemical reaction. Therefore, the observation supports the conclusion that a chemical change occurred.Rate this question:
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- 23.
A student has two solid samples of the same substance. Which property do the substances MOST likely have in common
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Density
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Mass
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Shape
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Volume
Correct Answer
A. DensityExplanation
The correct answer is density. Density is a property that describes the mass of a substance per unit volume. Since the two solid samples are of the same substance, it is likely that they have the same density. Mass, shape, and volume are not necessarily properties that would be the same for two solid samples of the same substance.Rate this question:
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- 24.
Which is an example of a physical property?
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Ductility
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Flammability
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Reactivity
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Combustion
Correct Answer
A. Ductility -
- 25.
One way to classify substances is to determine their ratio of mass per unit volume, or their density. Which of the following types of substances would typically have the greatest density?
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Nonmetals
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Gases
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Liquids
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Metals
Correct Answer
A. MetalsExplanation
Metals typically have the greatest density compared to nonmetals, gases, and liquids. This is because metals have closely packed atoms or ions, resulting in a higher mass per unit volume. In contrast, nonmetals, gases, and liquids have less closely packed particles, leading to lower densities. Therefore, metals are known for their high density compared to other types of substances.Rate this question:
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- 26.
Vito threw a rock into the lake and observed it sink. His friend, Romeo, threw his apple in the lake and observed it float. What is the MOST LIKELY explanation for why the rock sank and the apple floated?
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The density of the apple was less than the water in the lake
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The density of the rock was less than the water in the lake
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The mass of the apple was greater than the rock
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The mass of the apple was less than the rock
Correct Answer
A. The density of the apple was less than the water in the lakeExplanation
The most likely explanation for why the rock sank and the apple floated is that the density of the apple was less than the water in the lake. Density is a measure of how much mass is contained in a given volume. If an object is less dense than the fluid it is placed in, it will float. In this case, the apple had a lower density than the water, allowing it to float, while the rock had a higher density, causing it to sink.Rate this question:
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- 27.
Which of the following is an irreversible change
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A log of wood burning
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Paper being shredded
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Salt dissolving in water
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An ice cube melting
Correct Answer
A. A log of wood burningExplanation
Burning a log of wood is an irreversible change because it involves a chemical reaction that cannot be easily reversed. The wood undergoes combustion, releasing heat, light, and gases, and transforming into ash. Once the wood is burned, it cannot be restored to its original form. On the other hand, shredding paper, dissolving salt in water, and melting an ice cube are all reversible changes as they can be undone by reversing the physical processes involved.Rate this question:
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- 28.
Jonas was making bread. The chart shows the steps in the recipe he was using. Steps in making bread
- combine the two cups of flour with sugar, and yeast
- heat milk, water, and butter until warm
- beat two minutes.
- add one egg and one cup of flour
- knead (press) the dough until it's smooth
- cover and place in a warm place so the dough can rise
- place in a pan and bake at 325 degrees F for 20 minutes
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Combining the flour with the sugar
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Kneading the dough until smooth
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Adding the egg and a cup of flour
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Baking the dough in the oven
Correct Answer
A. Baking the dough in the ovenExplanation
Baking the dough in the oven involves a chemical change. During the baking process, the heat causes the dough to undergo a series of chemical reactions. The yeast in the dough produces carbon dioxide gas, which causes the dough to rise. Additionally, the heat causes the proteins in the flour to denature and form a network, giving the bread its structure and texture. These chemical changes result in the transformation of the dough into bread.Rate this question:
- 29.
Chemical compounds undergo both physical and chemical changes. Which of the following is an example of a physical change
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Salt (NaCI) being dissolved into water
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Combining oxygen gas and hydrogen gas to form to form liquid water
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Reordering atoms in a molecule
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Heat being released when combining two substances
Correct Answer
A. Salt (NaCI) being dissolved into waterExplanation
When salt (NaCI) is dissolved into water, it undergoes a physical change. This is because the chemical composition of salt remains the same before and after dissolving. The sodium ions (Na+) and chloride ions (CI-) are simply separated and surrounded by water molecules, forming a solution. No new substances are formed, and the salt can be recovered by evaporating the water. Therefore, this process is an example of a physical change rather than a chemical change.Rate this question:
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- 30.
Ocean water moves around the earth because of
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Gyres differences
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Density differences
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Gyres similarities
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Ocean current similarities
Correct Answer
A. Density differencesExplanation
Ocean water moves around the earth because of density differences. Density is affected by various factors such as temperature, salinity, and pressure. When water becomes denser, it sinks and moves towards areas of lower density, creating a current. This movement of water is essential for redistributing heat, nutrients, and oxygen, and plays a crucial role in regulating Earth's climate and supporting marine life. Gyres, on the other hand, are large circular ocean currents that are driven by a combination of factors including wind patterns and the rotation of the Earth. While gyres can influence the movement of ocean water, it is primarily density differences that drive the overall circulation.Rate this question:
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- 31.
A brick is cut into small pieces. Which physical property do the small pieces have in common with the brick from which they came
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Density
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Length
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Shape
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Mass
Correct Answer
A. DensityExplanation
The small pieces of a brick would have the same density as the original brick. Density is a physical property that describes the amount of mass in a given volume. Since the small pieces come from the same brick, they would have the same mass as the original brick, but their volume would be smaller due to being cut into smaller pieces. Therefore, the density of the small pieces would remain the same as the original brick.Rate this question:
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- 32.
Which of the following is an example of a physical change
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Iron rusting
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Water boiling
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Paper burning
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Silver tarnishing
Correct Answer
A. Water boilingExplanation
Water boiling is an example of a physical change because it involves a change in the physical state of water from a liquid to a gas. The chemical composition of water remains the same during boiling, only the arrangement and movement of water molecules change. In contrast, iron rusting, paper burning, and silver tarnishing are examples of chemical changes because they involve the formation of new substances with different chemical properties.Rate this question:
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- 33.
Physical changes are
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Always reversible
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Always irreversible
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Reversible with some materials
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Irreversible with pure substances
Correct Answer
A. Reversible with some materialsExplanation
Physical changes are reversible with some materials because physical changes involve a change in the physical properties of a substance without altering its chemical composition. These changes can be reversed by applying certain conditions or using specific materials. For example, melting ice can be reversed by cooling it, or evaporating water can be reversed by condensing it. However, not all physical changes are reversible with all materials. Some physical changes, such as breaking glass or burning paper, are irreversible and cannot be undone. Therefore, the statement "reversible with some materials" accurately describes the nature of physical changes.Rate this question:
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- 34.
Which is an indication that a chemical change is taking place
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Iron changes color when heated
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Gas bubbles form in boiling water
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Solid wax forms when melted wax falls in ice water
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A gas forms when vinegar and baking soda are mixed
Correct Answer
A. A gas forms when vinegar and baking soda are mixedExplanation
When vinegar and baking soda are mixed, a gas forms. This is an indication of a chemical change because the reactants (vinegar and baking soda) combine to form a new substance (gas). Chemical changes involve the rearrangement of atoms and the formation of new bonds, resulting in the creation of different substances with different properties. In this case, the gas formation indicates a chemical reaction between the vinegar and baking soda.Rate this question:
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- 35.
When investigating a chemical reaction, one would expect the products to have:
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The same properties as the reactants have separately
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A mixture of the properties of the reactants
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Different properties than the reactants separately
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The same properties as only one of the reactants
Correct Answer
A. Different properties than the reactants separatelyExplanation
When investigating a chemical reaction, it is expected that the products will have different properties than the reactants separately. This is because during a chemical reaction, the bonds between atoms are broken and new bonds are formed, resulting in the rearrangement of atoms to form new molecules. This rearrangement leads to a change in the chemical composition and structure of the substances involved, resulting in different properties for the products compared to the reactants.Rate this question:
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- 36.
Which of the following will NOT occur when water undergoes a physical change?
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The motion of the molecules increases
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The molecules form new chemical bonds
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The molecules become less closely packed
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The kinetic energy of molecules increases
Correct Answer
A. The molecules form new chemical bondsExplanation
When water undergoes a physical change, such as melting or boiling, the molecules do not form new chemical bonds. Physical changes only involve a change in the state or form of a substance, without altering its chemical composition. In the case of water, its molecules may gain or lose energy, move more rapidly, or become less closely packed, but they do not form new chemical bonds.Rate this question:
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- 37.
Coppers and other metals are often used in making pots and pans to cook in. What property would BEST explain why?
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Conductivity because it is a chemical property
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Conductivity because it is a physical property
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Insulation because it is a chemical property
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Insulation because it is a physical property
Correct Answer
A. Conductivity because it is a physical propertyExplanation
Coppers and other metals are often used in making pots and pans because they have high conductivity, which is a physical property. This means that they can efficiently transfer heat from the stove to the food being cooked, allowing for even and quick cooking. Chemical properties, on the other hand, describe the behavior of substances in chemical reactions, which is not relevant in this context. Insulation, whether physical or chemical, would not be desirable in pots and pans as it would hinder heat transfer.Rate this question:
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- 38.
Which of the following processes rearranges atoms during a reaction
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Burning
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Cooling
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Crushing
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Evaporating
Correct Answer
A. BurningExplanation
Burning is a process that involves a chemical reaction where atoms rearrange to form new compounds. During burning, the fuel combines with oxygen to produce heat, light, and various byproducts. This rearrangement of atoms is a fundamental characteristic of chemical reactions, making burning the correct answer to the question. Cooling, crushing, and evaporating are physical processes that do not involve the rearrangement of atoms.Rate this question:
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- 39.
Which of the following is NOT a physical property that a substance can be classified by?
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Hardness
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Thermal conductivity
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Reactivity
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Density
Correct Answer
A. ReactivityExplanation
Reactivity is not a physical property that a substance can be classified by. Physical properties are characteristics that can be observed or measured without changing the composition of the substance. Hardness, thermal conductivity, and density are all physical properties that can be measured or observed. Reactivity, on the other hand, refers to how a substance reacts with other substances, which involves a chemical change rather than a physical characteristic.Rate this question:
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- 40.
Victor is trying to find the density of an unknown liquid. What other measurement must he find if he knows that he has 42 grams of liquid
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The liquid's mass in liters
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The liquids volume in grams
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The liquids mass in cubic centimeters
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The liquids volume in milliliters
Correct Answer
A. The liquids volume in millilitersExplanation
To find the density of a substance, Victor needs to know its mass and volume. He already knows the mass of the unknown liquid, which is 42 grams. Therefore, he must find the liquid's volume in milliliters in order to calculate its density.Rate this question:
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