Mixtures & Solutions (STAAR released items)

A student stirs 15 grams of each substance listed below into 200 milliliters of water to form four different mixtures. The student then tries to separate the water from each mixture by pouring the mixture through a kitchen tea strainer.

Which mixture can the student separate most easily with the strainer?

• salt and water

• gravel and water

• shampoo and water

• sugar and water

Answer explanation

The student can separate gravel and water most easily because gravel is a solid that does not dissolve in water, allowing it to be caught by the strainer, while the other mixtures involve substances that dissolve or form emulsions.

Tags

NGSS.MS-PS1-2

Some ways to separate mixtures are listed in the box.

A Student is given a beaker containing gravel and water. Which of these ways could the student NOT use to separate the gravel from the water?

• 1

• 2

• 3

• 4

Answer explanation

The student cannot use method 2 to separate gravel from water, as it likely involves mixing or dissolving, which would not effectively separate the solid gravel from the liquid water.

Some people add sugar to their hot tea. Which property of the sugar remains the same when the sugar is in the tea solution?

• The taste of the sugar remains the same.

• The size of the sugar crystals remains the same,

• The color of the sugar remains the same.

• The texture of the sugar remains the same.

Answer explanation

The taste of the sugar remains the same when dissolved in tea, as it does not change chemically. The other properties, such as size, color, and texture, may not be perceptible in the solution.

A student made a mixture using equal amounts of salt and pepper. The salt grains were about the same size as the pepper grains. What should the student do to most easily separate the pepper from the mixture?

• Use tweezers to remove each grain of pepper.

• Run a magnet through the mixture to attract the pepper.

• Put the mixture in water and then use a paper filter (coffee filter) to remove the pepper.

• Use a strainer with a fine wire screen to remove the pepper.

Answer explanation

Putting the mixture in water allows the salt to dissolve while the pepper remains solid. Using a paper filter will effectively separate the undissolved pepper from the saltwater solution, making it the easiest method.

A mixture of beads was placed in a container. The beads are of various sizes, and each one is made of either plastic, glass, or steel.

The mixture would be easy to separate, because _____________.

• all the beads are less dense than water.

• all the beads are solids.

• all the beads have the same mass.

• all the beads are attracted to a magnet.

Answer explanation

The mixture is easy to separate because all the beads are solids. This allows for physical separation methods, such as sorting by size or material, unlike liquids or gases which would be more challenging to separate.

A beaker with 115 mL of solution has a temperature of 21 degrees Celsius. The solution contains 5 g of salt and 115 mL of water. Students add two ice cubes to the solution and then stir the solution for 3 minutes.

Which properties of the solution changed as the ice cubes melted?

• The color and physical state of the solution changed.

• The temperature, mass, and volume of the solution changed.

• The temperature, mass, and volume of the salt changed.

• The physical state (solid, liquid, or gas) and temperature of the solution changed.

Answer explanation

As the ice cubes melted, the temperature of the solution decreased, the mass increased due to the added water from the ice, and the volume also increased. Thus, the correct choice is that the temperature, mass, and volume of the solution changed.

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

NGSS.MS-PS3-5

For an investigation a student put 100 mL of water at room temperature into each of three beakers. Then the student added a coin to Beaker R, 3 g of powdered drink mix to Beaker S, and 10 mL of lamp oil to Beaker T. The student stirred the contents of the beakers and then left them sitting on a lab table for 5 minutes.

Which diagram shows what the student most likely observed in each of the beakers after 5 minutes?

• 
• 
• 
• 

Tags

NGSS.MS-PS1-2

A student combined (mixed) powdered paint with water to make a small amount of blue liquid paint mixture. The student left the paint mixture in an open container. Several days later the student found the container and observed that changes had occurred (happened). What most likely happened to the mixture?

• The container was completely empty after the mixture evaporated into the air.

• The paint evaporated, leaving only clear water in the container.

• The water evaporated, leaving only a dry blue solid in the container.

• The paint mixture was lighter in color after some water evaporated.

Answer explanation

The water in the paint mixture likely evaporated over time, leaving behind the dry blue solid pigment. This explains why the container would have a residue of blue powder instead of liquid.

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

A student adds 10 grams of four different powders into four different beakers. The student then adds 100 mL of water to each beaker, stirs the mixtures, and allows them to sit for half an hour before recording observations. Which question is the student most likely trying to answer with this investigation?

• The student wants to know at what temperature the substances dissolve.

• The student wants to know how much water is needed to cause a substance to change state.

• The student wants to know what causes a substance to sink when put in water.

• The student wants to know which substances will dissolve in water.

Answer explanation

The student adds powders to water and observes the results, indicating they want to determine which substances dissolve in water, making this the most relevant question for their investigation.

When a powdered drink mix was added to water, the liquid turned orange. A student decided the taste was too strong, so he poured out half the liquid and added more water. Which of the following most likely occurred (happened) when more water was added?

• The physical state of the liquid changed.

• The orange color of the liquid became lighter.

• The liquid had a sweeter taste.

• Nothing changed.

Answer explanation

When more water was added, it diluted the powdered drink mix, causing the orange color to become lighter. This is a common effect of dilution, where the concentration of the colorant decreases.