Block 2_Chemistry B Pre-Test

2.

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.
Wait until after the laboratory session is over before picking up the glassware; there are less people around so it is safer.

Correct Answer

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

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 because broken glassware can be dangerous and may pose a risk to others in the lab. Following the teacher's instructions about proper clean-up and disposal of broken glassware is crucial to ensure the safety of everyone in the lab.

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3.

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.
A scientific hypothesis is a testable assumption, while a theory is a well-verified idea used to explain a broad range of phenomena.
Only a scientific hypothesis is subject to scrutiny, while a theory does not change.

Correct Answer

A. A scientific hypothesis is a testable assumption, while a theory is a well-verified idea used to explain a broad range of phenomena.

Explanation

A scientific hypothesis is a testable assumption, meaning 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 substantial amount of evidence and has stood up to rigorous testing. It is used to explain a broad range of phenomena and is considered a more comprehensive and established explanation compared to a hypothesis. The answer accurately describes the key difference between a hypothesis and a theory in the scientific context.

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4.

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

Correct Answer

A. Melting butter

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 altering the chemical composition of the substance. The molecules in the butter rearrange themselves when heated, causing the solid butter to turn into liquid. This change is reversible, as the melted butter can be cooled down and solidify again without any change in its chemical properties.

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5.

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

Correct Answer

A. The electron

Explanation

JJ Thomson discovered the electron in his experiments. By passing electrical current through a cathode ray tube, he observed a beam of negatively charged particles moving from the cathode (negative electrode) towards the anode (positive electrode). These particles were later identified as electrons, which are subatomic particles with a negative charge. This discovery revolutionized our understanding of atomic structure and laid the foundation for the development of modern atomic theory.

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6.

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

Correct Answer

A. All of the above

Explanation

Surface tension, capillary action, and high specific heat are all properties of liquid water that are 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" that allows insects to walk on water. Capillary action is the ability of water to move against gravity in narrow tubes, which is due to the adhesive forces between water molecules and the walls of the tube, as well as the cohesive forces between water molecules. High specific heat refers to the ability of water to absorb and retain heat, which is a result of the strong hydrogen bonding between water molecules that requires a lot of energy to break.

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7.

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

Correct Answer

A. The substance that is being dissolved

Explanation

In the formation of a solution, the solute refers to the substance that is being dissolved. This means that it is the substance that is being added to the solvent and undergoes the process of dissolution. The solute can be a solid, liquid, or gas, depending on the nature of the solution. It is important to note that the solute is not always a solid substance, as it can also be a liquid or a gas that is being dissolved in a solvent.

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8.

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.

Correct Answer

A. Thermal energy is absorbed by the surroundings.

Explanation

An endothermic reaction is a reaction that absorbs thermal energy from its surroundings. This means that the surroundings gain thermal energy while the system loses it. In this case, the correct answer is "Thermal energy is absorbed by the surroundings," which accurately describes an endothermic reaction.

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9.

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

Correct Answer

A. Look at the bottom part of the meniscus

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 in the cylinder, and it is caused by the adhesive forces between the liquid and the cylinder. By looking at the bottom part of the meniscus, we can ensure that we are measuring the true volume of the liquid. The top part of the meniscus may appear higher due to surface tension, while averaging the top and bottom parts may lead to an inaccurate measurement. Ignoring the meniscus and simply determining which mL line the liquid is closest to would also result in an imprecise measurement.

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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

Correct Answer

A. 1.51 x 10^24

Explanation

A mole is a unit used to measure the amount of a substance. Avogadro's number states that one mole of any substance contains 6.02 x 10^23 representative particles, which can be atoms, molecules, or ions. Therefore, if we have a 2.50 mole sample, we can calculate the number of representative particles by multiplying the number of moles (2.50) by Avogadro's number (6.02 x 10^23). The result is 1.51 x 10^24, which represents the number of representative particles in the given sample.

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Block 2_chemistry B Pre-test

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

Quiz Preview

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

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

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

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)

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

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

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

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

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