4.19 EOC Group Challenge

An unknown gas is colorless, odorless, and tasteless. The gas turns moist iron filings reddish-brown. It condenses to a liquid at -183 degrees Celsius. Which fact is a chemical property of the gas?

• It condenses at -183 degrees Celsius.

• It turns iron reddish-brown.

• It is odorless.

• It is colorless.

Tags

NGSS.MS-PS1-2

Margaret adds 25 grams of slat to a one-liter glass beaker filled up to its volume mark with pure water. She stirs the water until the salt crystals disappear. She shows the beaker to Marcus and tells him what she did. Then she challenges him to make a correct statement about the beaker's contents. Which one of the four choices below is NOT correct?

• It is a homogeneous mixture.

• It is a solution.

• Water is the solvent and salt is the solute.

• Its molecular formula is NAClH₂0.

Below are some nuclei containing different numbers of protons and neutrons. Which one is an isotope of potassium?

• 20 protons 20 neutrons

• 17 protons 22 neutrons

• 18 protons 21 neutrons

• 19 protons 19 neutrons

Answer explanation

The isotope of potassium has 19 protons and 19 neutrons, matching the option with 19 protons and 19 neutrons.

• 2, 2

• 3, 2

• 4, 2

• 4, 4

Answer explanation

The correct coefficients to balance the equation are 2 for Na and 2 for NaF, resulting in 2Na + F2 -> 2NaF. Therefore, the correct choice is 2, 2.

Tags

NGSS.MS-PS1-5

A radioactive substance has a half-life of 40 years. What fraction of the sample will remain at the end of 160 years?

• 1/2

• 1/4

• 1/8

• 1/16

Answer explanation

After 160 years (4 half-lives), 1/2 * 1/2 * 1/2 * 1/2 = 1/16 of the sample will remain, so the correct answer is 1/16.

Tags

NGSS.HS-PS1-8

Which one of the following correctly shows the bonding that holds the atoms together?

• CaO: metallic bond

• SO₂

• KCl

• MgCl₂

Answer explanation

The correct choice, KCl, shows ionic bonding where potassium (K) donates an electron to chlorine (Cl) resulting in an electrostatic attraction between the ions.

Tags

NGSS.HS-PS1-1

NGSS.HS-PS1-3

If the distance between two objects is increased by a factor of four, what happens to the force of gravity between them?

• it is 1/16 as great

• it is 1/4 as great

• it does not change

• it is 4 times greater

Answer explanation

When the distance between two objects is increased by a factor of four, the force of gravity between them decreases by a factor of 16 (1/4 * 1/4 = 1/16). Therefore, it is 1/16 as great.

Tags

NGSS.HS-PS2-4

A wagon changes velocity from 2 km/hr to 6 km/hr over a period of 2 hours. What is the acceleration of the wagon?

• 2 km/h²

• 4 km/h²

• 6 km/h²

• 8 km/h²

Answer explanation

The acceleration can be calculated using the formula: acceleration = (final velocity - initial velocity) / time. Substituting the values, we get (6 km/hr - 2 km/hr) / 2 hours = 4 km/hr^2. Therefore, the correct answer is 4 km/h^2.

Without anyone helping her, Irma lifted her suitcase weighing 98 N a distance of 1.5 meters onto the luggage rack of the train car. How much work did she do?

• 65.3 J

• 65.3J

• 147 J

• 147 N

Answer explanation

Irma did 147 J of work because work done = force x distance, so 98 N x 1.5 m = 147 J.

As a sled slides down a hill, potential energy is converted to kinetic energy. However, after the ride is over, the amount of kinetic energy does not equal the amount of potential energy. This fact appears to contradict the law of conservation of energy. Why is this NOT true?

• The measurements are incorrect.

• The "missing" energy was converted to heat energy because of sliding friction.

• The law of conservation has exceptions.

• Some of the potential energy was converted to mass as the sled slid down the hill.

Answer explanation

The 'missing' energy was converted to heat energy because of sliding friction.

Tags

NGSS.MS-PS3-4

NGSS.MS-PS3-5