Soluble and Insoluble - progress learning

Which of these solids is insoluble in water?

• Sand

• Sugar

• Common salt

• Jello powder

Answer explanation

Sand is insoluble in water, meaning it does not dissolve. In contrast, sugar, common salt, and Jello powder all dissolve in water, making them soluble. Therefore, sand is the correct choice.

A mixture of sawdust, gravel, sand, and salt is placed in a beaker of water. Only one solid will dissolve. It is:

• Gravel

• Salt

• Sand

• Sawdust

Answer explanation

In the mixture, only salt is soluble in water. Gravel, sand, and sawdust do not dissolve, making salt the correct answer as it readily dissolves, forming a solution.

Anna is making sweet tea for the class picnic. She boils the water and then soaks the tea bags to get the perfect color. She decides to add sugar to the tea to sweeten it and ice to make it cold. When should she add the sugar?

• After the tea cools to room temperature

• Before the tea cools to room temperature

• It will not matter when she adds the sugar

• After the tea cools and ice cubes have been added

Answer explanation

Adding sugar before the tea cools ensures it dissolves properly, enhancing the sweetness. If added after cooling, the sugar may not dissolve well, resulting in a less sweet tea.

Anna decides to make iced tea for the class picnic. She wants the drink to be sweet and cold. Anna adds 1 cup of sugar to the pitcher of tea, but she notices that some of the sugar is still at the bottom of the pitcher. She decides to stir the tea and sugar. What is Anna actually doing to increase the rate of dissolving?

• Increasing the molecular motion

• Increasing the pressure in the solution

• Increasing the temperature of the solution

• Decreasing the temperature of the solution

Answer explanation

By stirring the tea, Anna increases the molecular motion of the sugar and tea, which helps the sugar dissolve faster. This is because increased motion allows sugar molecules to interact more with the solvent, enhancing the dissolving process.

Josh noticed that when he makes hot tea he can dissolve more sugar in the cup than he can when he mixes sugar in the same amount of cold, iced tea. This is because solubility increases for most solids as the temperature of the solution increases. Which graph represents this concept?

• Graph A

• Graph B

• Graph C

• Graph D

Answer explanation

Graph A correctly illustrates that solubility increases with temperature, showing more sugar dissolving in hot tea compared to cold tea. This aligns with Josh's observation about sugar solubility in different temperatures.

Think about the substances of each mixture. Which substance is soluble in its mixture?

• Sugar in water

• Sand in water

• Oil in water

• Pebbles in sand

Answer explanation

Sugar dissolves in water, forming a homogeneous solution, while sand, oil, and pebbles do not dissolve in their respective mixtures. Therefore, the only soluble substance in this context is sugar in water.

Think about the substances in the solutions listed below. What is true about each substance?

• Each substance dissolves in the water.

• None of the substances can be dissolved.

• Each substance changes the color of water.

• Each substance causes the water to dissolve.

Answer explanation

Each substance listed dissolves in water, meaning they can interact with water molecules and become part of the solution. This confirms that the correct choice is that each substance dissolves in the water.

Franklin added a solid yellow dye tablet to each of these beakers. One beaker (A) contained cold water, and the other beaker (B) contained hot water. He took this picture after ten seconds to compare the results. What is Franklin most likely investigating?

• He is investigating the effect temperature has on the movement of molecules.

• He is investigating how food coloring tablets affect the temperature of water.

• He is investigating how to create new colors by mixing two or more other colors.

• He is investigating the effects of evaporation on water mixed with colored tablets.

Answer explanation

Franklin is likely investigating how temperature affects molecular movement, as the dye will spread faster in hot water (beaker B) than in cold water (beaker A), demonstrating the relationship between temperature and molecular activity.

Tags

NGSS.MS-PS1-4

Mr. Luna-Gonzalez filled two pans with water. One pan held water heated to 60°. The other pan's water was heated to 90°. He poured two teaspoons of chocolate powder into each pan. His students watched as he stirred the powder in the 60° water until it completely dissolved. What will Mr. Luna-Gonzalez's students observe as he stirs the chocolate powder in the 90° water?

• The chocolate powder will dissolve faster.

• The chocolate powder will dissolve more slowly.

• The chocolate powder will not dissolve completely.

• The chocolate powder will stick to the sides of the pan.

Answer explanation

The chocolate powder will dissolve faster in the 90° water because higher temperatures increase the kinetic energy of the molecules, allowing the powder to interact more quickly with the water and dissolve more efficiently.

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

NGSS.MS-PS3-5

James and Aiden are preparing a demonstration for science to observe the difference between a mixture and a solution. First, they pour water into two cups. Then, they add salt into one cup and pepper into the other. After the cups are stirred, what conclusion should they make?

• The cup with the water and salt is a mixture because the salt can easily be separated.

• The cup with the water and salt is a solution because the salt is evenly mixed and disappears. The cup with the water and pepper is a mixture because the pepper can easily be seen floating at the top.

• The cup with the water and salt is a solution because it can be easily separated. The cup with the water and pepper is a mixture because the pepper mixes evenly.

• The cup with the water and salt is a solution because the ingredients share the same physical properties.

Answer explanation

The cup with water and salt forms a solution as the salt dissolves and is not visible, while the cup with water and pepper is a mixture since the pepper remains visible and can be separated easily.