Rate of Dissolving

Rate of Dissolving

Vocabulary

If you’re like Tanya in this picture, you prefer your iced tea sweetened with sugar. Sweetened iced tea is a solution in which solid sugar (the solute) is dissolved in cold liquid tea, which is mostly water (the solvent). When you add sugar to tea, particles of water pull apart particles of sugar. The particles of sugar spread throughout the tea, making all of it taste sweet.

Open Ended

Did you ever get impatient and start drinking a sweetened drink before all the sugar has dissolved? As you drink the last few drops, you notice that some of the sugar is sitting on the bottom of the container.

What could you do to dissolve the sugar faster?

One factor that affect the rate of dissolving is:

Stirring

• Stirring a solute into a solvent speeds up the rate of dissolving because it helps distribute the solute particles throughout the solvent. .

• For example, when you add sugar to iced tea and then stir the tea, the sugar will dissolve faster

• If you don’t stir the iced tea, the sugar may eventually dissolve, but it will take much longer.

One factor that affect the rate of dissolving is: Temperature

• The temperature of the solvent is another factor that affects how fast a solute dissolves. Generally, a solute dissolves faster in a warmer solvent than it does in a cooler solvent because particles have more energy of movement. 

• For example, if you add the same amount of sugar to a cup of hot tea and a cup of iced tea, the sugar will dissolve faster in the hot tea.

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One factor that affect the rate of dissolving is: Particle Size

• Smaller particles have greater surface area. With greater surface area, there can be more contact between particles of solute and solvent

• If you put granulated sugar in a glass of iced tea, it will dissolve more quickly than the same amount of sugar in a cube, because all those tiny particles of granulated sugar have greater total surface area than a single sugar cube.

  
  

Multiple Choice

True or False

The rate of dissolving of a solute in a solvent is faster when the solute and solvent are stirred.

• True

• False

Multiple Choice

True or False

The rate of dissolving is affected if the solute consists of smaller particles with more surface area.

• True

• False

Multiple Choice

You want to make chocolate milk using Hershey's syrup. How could you speed up the rate of the syrup dissolving in your milk?

• Put the syrup in the fridge to cool before putting it in the milk

• Put the syrup in the milk and let it sit

• Increase the amount of syrup you put into the milk

• Warm up the syrup before putting it into the milk

Multiple Choice

Jackson is making dinner and is trying to dissolve salt into a pot of water. The salt is dissolving slowly. What should Jackson do to speed up the rate of dissolving?

• He should put larger salt particles in the water.

• He should heat the water to a higher temperature.

• He should completely stop stirring the pot of water.

• He should slow down the speed he is stirring the pot.

Multiple Choice

What combination would dissolve a solid solute the fastest?

• high temperature, no stirring

• no heat, no stirring

• sugar cube, no heat

• high temperature, stirring

Multiple Choice

Which of the following statements is true about how using smaller salt crystals would affect the rate of making a salt solution in water?

• Smaller crystals increase the surface area and slow down dissolving.
• Smaller crystals decrease the surface area and speed up dissolving.
• Smaller crystals increase the surface area and speed up dissolving.
• Smaller crystals decrease the surface area and slow down dissolving.

Multiple Choice

The smaller the particle size the faster the rate of dissolution (rate of dissolving).

• True

• False

Multiple Choice

Stirring the solution increases the rate of dissolution (rate of dissolving).

• True

• False