1.
Classify the following questions as either chemical or physical properties:
Question: Is shiny and silvery
Correct Answer
B. Physical property
Explanation
The given question describes a characteristic of an object, specifically its appearance. Shiny and silvery are physical properties because they can be observed and measured without changing the chemical composition of the object. Chemical properties, on the other hand, involve the behavior of substances in chemical reactions or their ability to undergo changes at the molecular level.
2.
Melts easily
Correct Answer
A. Chemical
Explanation
The fact that something melts easily is an indication that it undergoes a chemical change rather than a physical change. Physical changes involve only a change in state or appearance, such as melting, freezing, or evaporating, while chemical changes involve a rearrangement of atoms and the formation of new substances. Therefore, the ability to melt easily suggests that the substance is undergoing a chemical change.
3.
Burns in air
Correct Answer
A. Chemical
Explanation
The fact that burns in air is categorized as a chemical reaction rather than a physical one can be explained by the changes that occur during the process. When a substance burns in air, it undergoes a chemical reaction with oxygen, leading to the formation of new substances. This reaction involves the breaking and forming of chemical bonds, resulting in the release of heat and light. In contrast, physical changes do not involve the formation of new substances or the breaking of chemical bonds. Therefore, burns in air are considered chemical reactions.
4.
Has a density of 2.3 g/mL
Correct Answer
B. Physical
Explanation
The given statement "has a density of 2.3 g/mL" refers to a physical property of a substance. Density is a characteristic property of matter that describes how closely packed the molecules are in a given volume. It is a physical property because it can be measured without changing the identity or composition of the substance. Chemical properties, on the other hand, describe how a substance interacts with other substances and involve changes in composition or identity. Therefore, the correct answer is physical.
5.
Tarnishes in moist air
Correct Answer
A. Chemical
Explanation
When an object tarnishes in moist air, it undergoes a chemical reaction. Tarnishing typically occurs when metals react with oxygen and moisture in the air, forming a layer of corrosion on the surface. This process is a chemical change because the composition of the metal is altered as it forms a new compound through the reaction with oxygen. It is not a physical change because there is a chemical transformation happening, rather than a change in the physical state or properties of the metal.
6.
Classify the following questions as either chemical or physical CHANGES:
Question: Ice melting in a drink
Correct Answer
B. Physical change
Explanation
The given question "Ice melting in a drink" is classified as a physical change. This is because the change of state from solid (ice) to liquid (water) is a physical change, where the molecules rearrange themselves without any alteration in their chemical composition. In this case, the ice is still made up of water molecules, but they are transitioning from a solid state to a liquid state due to the increase in temperature.
7.
Sugar added to lemonade
Correct Answer
A. Chemical change
Explanation
When sugar is added to lemonade, it undergoes a chemical change. This is because the sugar molecules break down into smaller molecules, such as glucose and fructose, through a process called hydrolysis. This change is irreversible and results in a new substance with different properties than the original sugar. Therefore, the addition of sugar to lemonade is an example of a chemical change.
8.
Mixing vinegar and baking soda to generate bubbles
Correct Answer
A. Chemical change
Explanation
When vinegar and baking soda are mixed together, a chemical reaction occurs. The reaction produces carbon dioxide gas, which is responsible for the formation of bubbles. This indicates that a new substance is being formed, as the properties of the vinegar and baking soda have changed. Therefore, the mixing of vinegar and baking soda to generate bubbles is an example of a chemical change.
9.
Plants using carbon dioxide and water to form oxygen and sugar
Correct Answer
A. Chemical change
Explanation
The given answer is a chemical change because it describes the process of plants using carbon dioxide and water to form oxygen and sugar. In this process, the substances are undergoing a chemical reaction, resulting in the formation of new substances with different properties. This is different from a physical change where the substances may change in form or state but their chemical composition remains the same.
10.
Changes of state are physical changes.
Correct Answer
A. True
Explanation
Changes of state refer to the physical transformation of matter from one state (solid, liquid, or gas) to another. These transformations do not involve any chemical reactions or changes in the chemical composition of the substance. Therefore, changes of state are indeed physical changes, making the statement "Changes of state are physical changes" true.
11.
Categorize the following questions as either absorbing or releasing energy:
Question: solid carbon dioxide going to carbon dioxide gas
Correct Answer
B. Releasing energy
Explanation
When solid carbon dioxide (dry ice) transitions into carbon dioxide gas, it undergoes a process called sublimation. This transition from a solid to a gas requires energy to break the intermolecular forces holding the solid together, and hence it absorbs energy from the surroundings. Therefore, the correct answer is "absorbing energy."
12.
Rubbing alcohol evaporating
Correct Answer
B. Releasing energy
Explanation
Rubbing alcohol, also known as isopropyl alcohol, evaporates easily due to its low boiling point. During the evaporation process, the alcohol molecules gain enough energy from their surroundings to overcome the forces holding them together in the liquid state. As a result, they transform into a gaseous state and are released into the air. This release of alcohol molecules in the form of vapor indicates that energy is being released in the process of evaporation.
13.
Aluminum solidifying in a mold
Correct Answer
A. Absorbing energy
Explanation
When aluminum solidifies in a mold, it undergoes a phase change from liquid to solid. During this process, energy is absorbed from the surroundings in order to break the intermolecular bonds and arrange the atoms into a solid structure. This absorption of energy is necessary for the solidification to occur. Therefore, the correct answer is absorbing energy.
14.
Chocolate melting
Correct Answer
B. Releasing energy
Explanation
When chocolate melts, it changes from a solid to a liquid state. This phase change requires energy, which is absorbed by the chocolate. However, when the chocolate solidifies again, it releases the absorbed energy back into its surroundings. Therefore, the correct answer is "releasing energy."
15.
Calculate the density of a rock that has a mass of 454g and a volume of 100 cubic centimeters.
Correct Answer
C. 4.54 g/ml
Explanation
The density of a substance is calculated by dividing its mass by its volume. In this case, the mass of the rock is given as 454g and the volume is given as 100 cubic centimeters. Therefore, the density can be calculated as 454g/100 cubic centimeters, which is equal to 4.54 g/ml.
16.
Anything that takes up space and has mass is the definition of ___________________.
Correct Answer
C. Matter
Explanation
Matter is defined as anything that takes up space and has mass. It includes solids, liquids, and gases, all of which have mass and occupy physical space. Therefore, matter is the correct answer to this question.
17.
Which of the following is a compound?
Correct Answer
D. Water
Explanation
Water is a compound because it is made up of two different elements, hydrogen and oxygen, which are chemically bonded together. Sodium, chlorine, and iodine are all elements, not compounds, as they consist of only one type of atom.
18.
Which of the following is a mixture?
Correct Answer
D. Sulfur
Explanation
Sulfur is a mixture because it is composed of different types of atoms bonded together. It is made up of sulfur molecules, which contain multiple sulfur atoms bonded together. This arrangement of atoms makes sulfur a mixture rather than a pure substance.
19.
Which of the following assumptions is not part of the kinetic theory?
Correct Answer
D. Particles are smaller at lower temperatures
Explanation
The assumption that particles are smaller at lower temperatures is not part of the kinetic theory. The kinetic theory states that all matter is made up of tiny particles, which are always in motion. It also states that particles move faster at higher temperatures. However, it does not make any assumptions about the size of particles changing with temperature.
20.
Three common states of matter are ___________________.
Correct Answer
C. Solid, liquid, gas
Explanation
The correct answer is solid, liquid, gas. These are the three common states of matter. Solids have a definite shape and volume, liquids have a definite volume but no definite shape, and gases have no definite shape or volume. This answer accurately identifies the three states of matter based on their properties.
21.
Which of the following is a physical change?
Correct Answer
A. Melting ice cubes
Explanation
Melting ice cubes is a physical change because it involves a change in the state of matter from solid to liquid, without altering the chemical composition of the substance. The molecules in the ice cubes are rearranged and gain enough energy to overcome the forces holding them together, resulting in the formation of liquid water. This change is reversible, as the liquid water can be frozen back into ice cubes.
22.
When steam rises from a hot cup of water, the particles have ___________________.
Correct Answer
D. Gained enough energy to evaporate
Explanation
When steam rises from a hot cup of water, it indicates that the particles have gained enough energy to evaporate. Evaporation occurs when the particles of a liquid gain sufficient energy to break free from the surface and enter the gas phase. In this case, the heat from the hot cup of water transfers energy to the water particles, increasing their kinetic energy and allowing them to escape into the air as steam. Therefore, the correct answer is "gained enough energy to evaporate."