2024 Semester Final

Which of the following substances would be identified as a compound?

Select TWO correct answers.

• H₂

• O

• CO

• NaBr

• N₂

Answer explanation

A compound consists of two or more elements chemically bonded. CO (carbon monoxide) and NaBr (sodium bromide) are compounds, while H2 (hydrogen gas), O (oxygen gas), and N2 (nitrogen gas) are diatomic molecules, not compounds.

Tags

NGSS.MS-PS1-1

Students were asked to identify substances as either elements or compounds. The table shows their answers.

Which students identified the substances correctly?

• Riley and Taylor

• Only Pablo

• Juliet and Caren

• Riley, Juliet, and Pablo

Answer explanation

Juliet and Caren correctly identified the substances as elements or compounds. Their answers align with the definitions, while the others made errors in classification.

Tags

NGSS.MS-PS1-1

Students were asked to identify substances as either elements or compounds. The table shows their answers. Juliet and Caren identified the substances correctly.

Which statement BEST supports their answer?

• Subscripts mean that the substance contains elements only.

• The difference between elements and compounds is determined by how the substance is being used.

• Three or more elements create a compound. Only C₆H₁₂O₆ has three or more elements.

• Compounds contain more than one element, and C₄ is a pure substance that contains one element.

Answer explanation

The correct choice states that compounds contain more than one element, while C4 is a pure substance with only one element. This clearly distinguishes between elements and compounds, supporting Juliet and Caren's correct identification.

Tags

NGSS.MS-PS1-1

Students are asked to determine whether a substance is considered an element or a compound.

Identify the following:

C₄

Na

W

• Elements

• Compounds

Answer explanation

C4, Na, and W are all symbols for elements on the periodic table. C4 represents carbon, Na is sodium, and W is tungsten. Since they are not made of two or more different elements, they are classified as elements.

Tags

NGSS.MS-PS1-1

Students are asked to determine whether a substance is considered an element or a compound.

Identify the following:

H₂O

MgO₂

C₆H₁₂O₆

• Elements

• Compounds

Answer explanation

H2O, MgO2, and C6H12O6 are all compounds because they consist of two or more different elements chemically bonded together. Elements consist of only one type of atom, while compounds are made from combinations of different atoms.

Tags

NGSS.MS-PS1-1

What kind of pure substance forms when two or more different elements are chemically combined and are represented by a chemical formula?

• element

• compound

• mixture

• solution

Answer explanation

A compound is a pure substance formed when two or more different elements chemically combine, represented by a chemical formula. In contrast, elements are single substances, while mixtures and solutions involve combinations without chemical bonding.

Tags

NGSS.MS-PS1-5

Determine which example(s) best describes conduction. There may be more than one correct answer.

• touching a hot seat belt when you get into a car

• warm air that rises to the ceiling in your house

• heat emitted by an electric heater

• hot air rising above a fire

Answer explanation

Conduction occurs when heat is transferred through direct contact. Touching a hot seat belt transfers heat from the belt to your skin, illustrating conduction. The other options describe convection or radiation.

Determine which example(s) best describes radiation. There may be more than one correct answer.

• touching a hot seat belt when you get into a car

• warm air that rises to the ceiling in your house

• heat emitted by an electric heater

• hot air rising above a fire

Answer explanation

The correct choice, 'heat emitted by an electric heater', describes radiation as it involves the transfer of heat through electromagnetic waves. The other options involve conduction or convection, not radiation.

Determine which example(s) best describes convection. There may be more than one correct answer.

• touching a hot seat belt when you get into a car

• warm air that rises to the ceiling in your house

• heat emitted by an electric heater

• hot air rising above a fire

Answer explanation

Convection is the transfer of heat through the movement of fluids. 'Warm air that rises to the ceiling in your house' and 'hot air rising above a fire' are both examples of convection, as they involve the movement of warm air.

Tags

NGSS.MS-ESS2-5

Whether watching water boil or sitting by a campfire, heat energy travels in one of three ways: conduction, convection, or radiation.

Determine which of the following are examples of conduction.

• an egg frying in pan

• feeling the heat of the Sun

• touching a hot bowl of soup

• a hot air balloon floating

• warming up next to a heater

Answer explanation

Conduction occurs when heat is transferred through direct contact. An egg frying in a pan and touching a hot bowl of soup are both examples of conduction, as heat moves directly from the hot surfaces to the food or your hand.

Tags

NGSS.MS-PS3-3