Pre-test Chemistry B Quiz Block 4

1. If a piece of laboratory glassware breaks, a student should immediately: (AZ HS Science S1:C2:PO1)

Notify his/her lab partner and then begin clean-up.

Notify his/her teacher and students nearby of broken glassware, then follow instructions about proper clean-up and disposal of broken glassware.

Grab paper towels and begin cleaning up the mess.

If a piece of laboratory glassware breaks, it is important for the student to immediately notify his/her teacher and students nearby of the broken glassware. This is necessary to ensure the safety of everyone in the lab and to prevent any injuries or accidents. The student should then follow the instructions given by the teacher about the proper clean-up and disposal of the broken glassware. This is important to prevent any further damage or harm and to maintain a safe environment in the laboratory.

Explanation

If a piece of laboratory glassware breaks, it is important for the student to immediately notify his/her teacher and students nearby of the broken glassware. This is necessary to ensure the safety of everyone in the lab and to prevent any injuries or accidents. The student should then follow the instructions given by the teacher about the proper clean-up and disposal of the broken glassware. This is important to prevent any further damage or harm and to maintain a safe environment in the laboratory.

2. Which of the following institutions employs scientists? (AZ HS Science S2:C1:PO3)

Hospitals

Universities

Corporations

All of the above

All of the above institutions employ scientists. Hospitals often have research departments where scientists conduct medical research. Universities employ scientists as professors and researchers in various fields. Corporations, especially those in the pharmaceutical and technology industries, employ scientists for research and development purposes. Therefore, all three institutions mentioned employ scientists.

Explanation

All of the above institutions employ scientists. Hospitals often have research departments where scientists conduct medical research. Universities employ scientists as professors and researchers in various fields. Corporations, especially those in the pharmaceutical and technology industries, employ scientists for research and development purposes. Therefore, all three institutions mentioned employ scientists.

3. Which of the following is an example of a physical change? (AZ HS Science S5:C1:PO1)

Rusting bicycle chain

Melting butter

Fireworks exploding

Baking a cake

Melting butter is an example of a physical change because it involves a change in the state of matter from solid to liquid, without any change in the chemical composition of the substance. The molecules in the butter rearrange themselves when heated, causing it to change from a solid state to a liquid state. This change is reversible, as the melted butter can solidify again when cooled.

Explanation

Melting butter is an example of a physical change because it involves a change in the state of matter from solid to liquid, without any change in the chemical composition of the substance. The molecules in the butter rearrange themselves when heated, causing it to change from a solid state to a liquid state. This change is reversible, as the melted butter can solidify again when cooled.

4. In his experiments, JJ Thomson passed electrical current through two positively charged plates at opposite ends of a cathode ray tube from which all air had been removed. What did he discover? (AZ HS Science S5:C1:PO7)

The neutron

The electron

The nucleus

The proton

JJ Thomson discovered the electron. He passed electrical current through a cathode ray tube with positively charged plates at opposite ends and no air. He observed that a beam of particles, called cathode rays, moved from the negatively charged cathode towards the positively charged anode. This led him to conclude that these particles were negatively charged and much smaller than atoms, which he called electrons. This discovery revolutionized our understanding of atomic structure and laid the foundation for the development of modern physics.

Explanation

JJ Thomson discovered the electron. He passed electrical current through a cathode ray tube with positively charged plates at opposite ends and no air. He observed that a beam of particles, called cathode rays, moved from the negatively charged cathode towards the positively charged anode. This led him to conclude that these particles were negatively charged and much smaller than atoms, which he called electrons. This discovery revolutionized our understanding of atomic structure and laid the foundation for the development of modern physics.

5. Which of the following best describes the difference between a scientific hypothesis and a scientific theory? (AZ HS Science S1:C1:PO1)

Once a scientific hypothesis has been proven, it becomes known as a theory.

A scientific hypothesis must be testable, while a theory does not have to be tested.

Only a scientific hypothesis is subject to scrutiny, while a theory does not change.

A scientific hypothesis is a testable assumption, meaning that it can be experimentally or observationally tested to determine its validity. On the other hand, a scientific theory is a well-verified idea that has been supported by a significant amount of evidence and is used to explain a wide range of phenomena. The main difference between the two is that a hypothesis is a tentative explanation that is subject to testing and can be either supported or rejected, while a theory is a well-established and widely accepted explanation that has withstood rigorous testing and scrutiny.

Explanation

A scientific hypothesis is a testable assumption, meaning that it can be experimentally or observationally tested to determine its validity. On the other hand, a scientific theory is a well-verified idea that has been supported by a significant amount of evidence and is used to explain a wide range of phenomena. The main difference between the two is that a hypothesis is a tentative explanation that is subject to testing and can be either supported or rejected, while a theory is a well-established and widely accepted explanation that has withstood rigorous testing and scrutiny.

6. Which of the following describes an endothermic reaction? (AZ HS Science S5:C4:PO10)

Thermal energy is released by the system.

Thermal energy is absorbed by the surroundings.

Thermal energy is not transferred.

The initial and final temperatures of the system remains the same.

An endothermic reaction is a reaction that absorbs thermal energy from its surroundings. This means that the surroundings will experience a decrease in temperature as the system absorbs heat. Therefore, the statement "Thermal energy is absorbed by the surroundings" accurately describes an endothermic reaction.

Explanation

An endothermic reaction is a reaction that absorbs thermal energy from its surroundings. This means that the surroundings will experience a decrease in temperature as the system absorbs heat. Therefore, the statement "Thermal energy is absorbed by the surroundings" accurately describes an endothermic reaction.

7. Which of the following properties of liquid water are caused by water's intermolecular forces (hydrogen bonds)? (AZ HS Science S5:C4:PO12)

Surface tension

Capillary action

High specific heat

All of the above

The properties of surface tension, capillary action, and high specific heat are all caused by water's intermolecular forces, specifically hydrogen bonds. Surface tension is the result of the cohesive forces between water molecules at the surface, which creates a "skin" or "film" on the surface. Capillary action is the ability of water to move against gravity in narrow spaces due to the adhesive forces between water and the surface of the container. High specific heat refers to water's ability to absorb and retain heat, which is due to the strong hydrogen bonding between water molecules that requires a large amount of energy to break. Therefore, all of these properties are influenced by water's intermolecular forces.

Explanation

The properties of surface tension, capillary action, and high specific heat are all caused by water's intermolecular forces, specifically hydrogen bonds. Surface tension is the result of the cohesive forces between water molecules at the surface, which creates a "skin" or "film" on the surface. Capillary action is the ability of water to move against gravity in narrow spaces due to the adhesive forces between water and the surface of the container. High specific heat refers to water's ability to absorb and retain heat, which is due to the strong hydrogen bonding between water molecules that requires a large amount of energy to break. Therefore, all of these properties are influenced by water's intermolecular forces.

8. To accurately measure the volume of a typical liquid in a graduated cylinder, what should you do? (AZ HS Science S1:C2:PO3)

Look at the bottom part of the meniscus

Look at the top part of the meniscus

Average the top and bottom parts of the meniscus

Ignore the meniscus and determine which mL line the liquid is closet to

When measuring the volume of a liquid in a graduated cylinder, it is important to look at the bottom part of the meniscus. The meniscus is the curved surface of the liquid caused by capillary action. By looking at the bottom part of the meniscus, you are ensuring that the measurement is accurate and not affected by any distortion caused by the curved surface. This method allows for a more precise measurement of the liquid's volume.

Explanation

When measuring the volume of a liquid in a graduated cylinder, it is important to look at the bottom part of the meniscus. The meniscus is the curved surface of the liquid caused by capillary action. By looking at the bottom part of the meniscus, you are ensuring that the measurement is accurate and not affected by any distortion caused by the curved surface. This method allows for a more precise measurement of the liquid's volume.

9. In the formation of a solution, the solute is: (AZ HS Science S5:C1:PO4)

The substance which does the dissolving

Always the liquid substance

The substance that is being dissolved

Always the solid substance

In the formation of a solution, the solute is the substance that is being dissolved. When a solution is formed, one substance, called the solute, dissolves in another substance, called the solvent. The solute can be a solid, liquid, or gas, but in this case, it refers to the substance that is being dissolved.

Explanation

In the formation of a solution, the solute is the substance that is being dissolved. When a solution is formed, one substance, called the solute, dissolves in another substance, called the solvent. The solute can be a solid, liquid, or gas, but in this case, it refers to the substance that is being dissolved.

10. If you have a 2.50 mole sample of a substance how many representative particles does this represent? (AZ HS Science S5:C4:PO5)

2.50 x 10^23

6.02 x 10^24

1.51 x 10^24

2.50 x 10^24

A mole is a unit used to measure the amount of a substance. Avogadro's number, 6.02 x 10^23, represents the number of representative particles (atoms, molecules, or ions) in one mole of a substance. To find the number of representative particles in a 2.50 mole sample, we multiply the number of moles by Avogadro's number. Therefore, the correct answer is 2.50 x 10^23 x 6.02 x 10^23 = 1.51 x 10^24.

Explanation

A mole is a unit used to measure the amount of a substance. Avogadro's number, 6.02 x 10^23, represents the number of representative particles (atoms, molecules, or ions) in one mole of a substance. To find the number of representative particles in a 2.50 mole sample, we multiply the number of moles by Avogadro's number. Therefore, the correct answer is 2.50 x 10^23 x 6.02 x 10^23 = 1.51 x 10^24.