Properties of Matter Review

Your lab group has been given a mixture of sand and water. The task at hand is to separate the sand from the water, producing a container of sand and a second container of water. Maria suggests using the procedure called crystallization but several other group members think that filtration would be the best way to separate the two. Provide support for the second separation method, filtration. All BUT ONE point is valid.

• 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.

  
  

Salt plus water. Two compounds mixed together to form a solution. The water is the solvent; the salt the solute. Students have been tasked with separating the two compounds from solution. One group set up the distillation apparatus you see here. Explain the concept used to separate the salt and water.

• 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.

One situation indicates a physical change rather than a chemical change. Which situation indicates a physical 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.

  
  

Mary Sue is making caramel ice cream. In the first part of the process, she combines a cup of sugar and a cup of water in a saucepan. She cooks the mixture over medium heat until the sugar melts and browns to a light amber color. Then she adds the same amount of water to the mixture along with a cup and a half of cream and milk.

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

During a science lab, some students added small pieces of magnesium ribbon to 10 mL of hydrochloric acid. They noticed that bubbles formed, the test tube got hot, and the magnesium disappeared.

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

  
  

Brad and Juan conducted several tests to determine the properties of silver metal. They noted that it was white, and conducted both electricity and heat. They computed the density to be 10.49 g/cm³. Silver did not react with water but in nitric acid, gas was released.

What evidence supports a chemical change in the silver?

• Silver conducts electricity.

  
  

• Silver reacts with nitric acid to produce a gas.

  
  

• The color of silver at room temperature is white.

  
  

• Silver conducted heat and as the temperature increased, became more malleable.

  
  

This flask originally held some copper wire and a clear solution of nitric acid. The two substances reacted and produced a brown gas and a blue solution. This reaction cannot be reversed. Evidence of a chemical reaction is shown by

• ice forming.

  
  

• steam rising.

  
  

• the formation of a gas.

  
  

• a change in state from a solid to a liquid.

  
  

The task in science lab: discover which solid substance, without tasting, is sugar. Donna and Dave have five substances to test, and unfortunately, two are white! "Let's heat them!" suggested Donna.

Did Donna have a reasonable solution to their problem?

Responses

• Yes, it would help narrow the search to salt or sugar.

  
  

• No, all four substances have pretty low melting points.

  
  

• No, it's impossible to reach these temperatures in a student lab.

  
  

• Yes, sugar's melting point is much lower than the other four solids.

  
  

From the data table, describe how you know a chemical reaction took place between sugar and oxygen.

• The solubility decreased.

  
  

• The density was not available on one of the reactants.

  
  

• Because sugar will dissolve in water and change the solubility.

  
  

• The chemical and physical properties of the products do not match the properties of the reactants.

  
  

Your science teacher gives you three liquids to pour into a jar. After pouring, the liquids layer as seen here. What property of matter allows the different liquids to layer in the jar?

• color

  
  

• density

  
  

• mass

  
  

• texture