Unit 3 Review: Properties of Matter

You are hired as a scrap metal dealer. A customer wants to sell you a piece of precious scrap metal. You know it is one of these common metals. You slowly heat the metal and it melts at 962 °C. You also take the density of the metal and find it to be roughly 10.5 g/cm³. What is the MOST LIKELY identity of the metal?

• copper

• gold

• silver

• zinc

Answer explanation

The metal melts at 962 °C and has a density of 10.5 g/cm³, which matches silver. Copper melts at 1085 °C, gold at 1064 °C, and zinc at 419 °C, making silver the most likely identity of the metal.

Which method is used to separate an insoluble solid from a liquid?

• Filtration

• Simple distillation

• Fractional distillation

• Crystallization

Answer explanation

Filtration is the method used to separate an insoluble solid from a liquid. It involves passing the mixture through a filter, allowing the liquid to pass while retaining the solid on the filter paper.

What is the purpose of simple distillation?

• To separate an insoluble solid from a liquid

• To separate a solvent from a solution

• To separate different liquids from a mixture

• To produce solid crystals from a solution

Answer explanation

The purpose of simple distillation is to separate a solvent from a solution by heating the solution to evaporate the solvent, which is then condensed back into liquid form, leaving impurities behind.

Which method is used to produce solid crystals from a solution?

• Filtration

• Simple distillation

• Fractional distillation

• Crystallization

Answer explanation

Crystallization is the method used to produce solid crystals from a solution. It involves the formation of solid crystals as the solution cools or evaporates, allowing the solute to come out of the solution.

Which point is NOT valid for the separation of sand and water using filtration?

• Sand is an insoluble solid that does not dissolve in water.

• The two parts of the mixture, sand and water, have different boiling points.

• Sand particles are large enough to be stopped by a piece of filter paper, separating the sand from the water.

• Although crystallization would separate the sand from the water, it would not provide a method to collect the water.

Answer explanation

The statement about boiling points is not valid for filtration, as filtration relies on particle size, not boiling points. Sand is separated from water because sand does not dissolve and is trapped by the filter paper.

The separation of salt and water in a solution is based on which concept?

• The separation of the water from the salt is based on the boiling point and condensing point of water.

• The separation is based on the temperature needed to change liquid water to a gas and then back again to a liquid: the boiling point.

• The separation of the two is based on different boiling points of the salt (higher) and the water (lower). When the solution is heated the water evaporates from the solution, leaving salt behind.

• The separation of the two is based on different boiling points of the salt (lower) and the water (higher). When the solution is heated the salt is transferred as water vapor collects in the condensing tube.

Answer explanation

The correct choice explains that the separation of salt and water is based on their different boiling points, with water having a lower boiling point. When heated, water evaporates, leaving the salt behind.

Which situation indicates a physical change rather than a chemical change?

• Solid copper melts to form liquid copper.

• A firecracker explodes on the fourth of July.

• Water reacts with the iron on your bicycle to form rust.

• Magnesium metal is mixed with hydrochloric acid and hydrogen gas is formed.

Answer explanation

The melting of solid copper to form liquid copper is a physical change because it alters the state of the substance without changing its chemical composition. The other options involve chemical reactions.

Which part of the preparation indicated a chemical change?

• melting the sugar

• mixing the sugar with water

• adding cream and milk to the mixture

• sugar changes from white to a light amber color

Answer explanation

The correct choice indicates a chemical change because the sugar's color changes from white to light amber, signifying a transformation in its chemical structure, unlike the other options which involve physical changes.

Which is a sign that a chemical reaction has taken place in this experiment?

• change in odor

• change in color

• release of heat energy

• disappearance of magnesium

Answer explanation

The disappearance of magnesium indicates a chemical reaction, as it transforms into a different substance. Other signs like odor, color change, or heat release may occur but are not definitive on their own.

What evidence supports a chemical change in the silver?

• Silver is white in color

• Silver conducts electricity

• Silver did not react with water

• Gas was released in nitric acid

Answer explanation

The release of gas when silver reacts with nitric acid indicates a chemical change, as it shows a transformation of substances. The other options describe physical properties or lack of reaction, which do not indicate a chemical change.