Katie's teacher has given her a sample that contains a mixture of salt, sand, and iron filings. What would be the best physical property to focus on for the first step in separating the mixture?

• Density

• Electrical conductivity

• Magnetism

• Melting point

Isopropyl alcohol has a density of 0.786 grams per cubic centimeter (g/cm3). An object has a mass of 13 grams (g) and a volume of 21 cubic centimeters (cm3). What will happen when the object is placed into isopropyl alcohol?

• The object will sink because it is less dense than isopropyl alcohol.

• The object will float because it is less dense than isopropyl alcohol.

• The object will sink because it is more dense than isopropyl alcohol.

• The object will float because it is more dense than isopropyl alcohol.

The table below compares the solubility of two substances in 100 milliliters (mL) of water. Based on the table, which of the following statements is true?

• The solubility of sucrose increases as more is dissolved.

• The solubility of sucrose decreases if temperature increases.

• The solubility of hydrochloric acid increases if more is dissolved.

• The solubility of hydrochloric acid increases as temperature increases.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-4

The formula for calculating density is D=M/V, where M represents mass and V represents volume. If the density of an unknown liquid is 1.6 g/cc, what is the mass of 800 cc of the unknown liquid in grams (g)?

• 0.002g

• 1.6g

• 500g

• 1280g

Acid reflux occurs when acid from a person's stomach escapes from the stomach and enters the esophagus, a flexible tube that leads into the stomach. Which substance would be best for neutralizing stomach acid?

• a substance with a pH of 9

• a substance with a pH of 5

• a substance with a pH of 1

• a substance with a pH of 7

Which statement best compares pure substances to mixtures?

• Pure substances contain small amounts of impurities. Mixtures contain large amounts of impurities.

• Pure substances must be made of two chemical materials. Mixtures can be made of only one chemical material.

• Pure substances are either compounds or elements. Mixtures are homogeneous or heterogeneous combinations.

• Pure substances are liquids dissolved in liquids or gases dissolved in gases. Mixtures are gases dissolved in liquids or solids dissolved in liquids.

Mixtures typically melt at different temperatures than the pure substances they are composed of. Brass is a mixture composed of copper and zinc, and it melts at temperatures between 820 degrees Celsius (°C) and 1030 degrees Celsius (°C). Why might different samples of brass melt at different temperatures?

• The samples are different in size and in volume.

• The samples have different shapes and masses.

• The samples are composed of different proportions of copper and zinc.

• The samples have the same amounts of copper and zinc melting at different temperatures.

Tags

NGSS.MS-PS3-4

Atomic theory describes the motion of particles in solids, liquids, and gases. Which statement best describes the particles in a given state of matter?

• The particles in gases have a fixed position but can vibrate.

• The particles in solids have a fixed position but can vibrate.

• The particles in solids are very close to each other but they are able to move past each other.

• The particles in gases are very close to each other but they are able to move past each other.

Tags

NGSS.MS-PS1-4

If a sample of gold were reduced to the smallest possible particles of pure gold, which statement would most accurately describe the result?

• The sample would be reduced to atoms of gold.

• The sample would be reduced to molecules of gold.

• The sample would be reduced to protons and neutrons of gold.

• The sample would be reduced to electrons and protons of gold.

Tags

NGSS.MS-PS1-1

Which of the following comparisons correctly describes subatomic particles?

• A neutron has a neutral charge and a mass larger than the mass of an electron.

• A neutron has a negative charge and a mass smaller than the mass of a proton.

• An electron has a negative charge and a mass larger than the mass of a proton.

• A proton has a positive charge and a mass smaller than the mass of an electron.