SC.5.P.8.2

DeShawn is getting a new fish tank ready for the fish he plans to buy. He has to dissolve salt crystals in the water. What would be the best thing to do to help the crystals dissolve quickly?

• heat the salt crystals

• crush the salt crystals

• cool the water in the tank

• use the largest salt crystals

Tags

NGSS.MS-PS3-4

Salim is studying how the rate of stirring affects the time it takes for salt to dissolve. He added 1 g of salt to each of four beakers filled with water, stirred the water at different speeds, and recorded how long it took for all the salt to dissolve each time. Salim’s results are shown in the following table. Stirring Time (sec) No stirring 25 Slow stirring 18 Medium stirring 10 Fast stirring 6 Which conclusion could Salim draw based on his results?

• Salt will not dissolve in water unless the water is stirred.

• Stirring a solution of water increases the rate at which a salt dissolves.

• Stirring a solution of water decreases the rate at which a salt dissolves.

• Stirring a solution of water has no effect on the rate at which a salt dissolves.

4. Four students are dissolving sugar in water to perform an experiment. Each student dissolved 1 tsp of sugar in 1 cup of hot water and stirred the water a different number of times. The students recorded how long it took for the sugar to dissolve in each cup. The results are shown in the following table.

Stirring        Time (sec)
zero stirs        28
two stirs        17
four stirs        11

Based on the data, what effect does stirring have on the time it takes for sugar to dissolve in water?

• Stirring the water makes the sugar dissolve faster.

• Stirring the water makes the sugar dissolve slower.

• Stirring the water has no effect on how fast the sugar dissolves.

• Stirring the water makes the sugar dissolve at the same rate as not stirring.

Tags

NGSS.MS-PS3-5

Which of the following happened as the number of stirs increased?

• The speed of dissolving increased.

• The speed of dissolving decreased.

• The amount of sugar dissolved increased.

• The amount of sugar dissolved decreased.

Tags

NGSS.MS-PS3-5

Mrs. Lopez is a chemist who is studying salt crystals. She wants to slow the rate at which the crystals dissolve in a solution of water. What could she do to slow the dissolving rate?

• Crush the salt.

• Stir the solution.

• Heat the solution.

• Cool the solution.

Tags

NGSS.MS-PS3-4

In a science experiment, Kayo added 1 tbsp of sugar to a flask filled with water. The diagram below shows how Kayo’s experiment looked. Which could Kayo do to speed up the dissolving process?

• Add more sugar to the flask.

• Place the flask in an ice bath.

• Shake the flask back and forth.

• Remove some water from the flask.

A group of students are studying how substances dissolve in water. Each student adds a 1-gram sample of material to 100 mL of water and stirs the liquid for 1 min. The table shows the substance each student tested.

• Imad tested table salt and Leah tested iron filings.

• Imad tested sugar and Leah tested sand.

• Imad tested oil and Leah tested copper filings.

• Imad tested baking soda and Leah tested plastic beads.

Tags

NGSS.MS-PS1-2

A solution is formed when one substance is dissolved in another. Mae has a solution in which water is the solvent. Which of these could be the solute?

• oil

• pebbles

• sand

• sugar

Gabrielle created a solution using a solute and a solvent. Which best describes a solution?

• a chemical change

• a chemical reaction

• any combination of two or more liquids

• an evenly distributed mixture of two or more substances

Andrea created a solution by adding food coloring to water. Her solution is also a mixture. Which of these is true of all solutions?

• They are all liquids.

• They all include water.

• The parts of all solutions are evenly mixed.

• The substances are always permanently combined.