Key Concepts

Adding energy (heating) boosts molecular motion.Increased molecular motion competes v the attraction in between solute molecules and also tends to do them come apart much more easily.Increased molecular movement causes more solvent molecule to call solute molecules and also pull on castle with an ext force, commonly resulting in more dissolving. Because different substances space made from various atoms, ions, or molecules, increased temperature will affect their dissolving to various extents.

Summary

Students revisit the dissolving M&M task from lesson 4. Lock will architecture an experiment to watch if temperature affects the quantity of dissolving of the sugar coating of an M&M.

Objective

Students will have the ability to identify and also control variables to architecture an experiment to check out whether the temperature the a solvent influence the rate at which a solute dissolves. College student will have the ability to explain, top top the molecular level, why raising temperature increases the price of dissolving.

Evaluation

Download the student activity sheet, and also distribute one per student when specified in the activity. The activity sheet will serve together the “Evaluate” ingredient of every 5-E lesson plan.

You are watching: Why does sugar melt faster than salt

Safety

Be sure you and the students wear properly fitting goggles. Warn students not to eat the M&M’s.

Materials because that Each Group

M&M"s (3 very same color)3 clear plastic cups1 paper of white paperRoom-temperature waterHot water (about 50 °C)Cold water (about 5 °C)

Materials because that the Demonstration

4 i graduated cylinders (50 mL)Hot water (about 50 °C)Cold water (about 5 °C)SaltSugarTablespoon2 small cups
Engage

Have students work in groups to architecture an experiment come investigate whether the temperature of water influence the lot of M&M coating that dissolves.

Remind student of the experiment they walk in class 4 in i m sorry they put an M&M in water and also watched the colored street coating dissolve. In the experiment, students used water and also then alcohol and also oil to watch if the solvent provided affects the dissolving of the M&M coating.

Ask students:

What can you investigate around M&M’s dissolve in water? If students carry out not suggest an altering the temperature of the water, ask even if it is they think the temperature of the water affects the lot of coating that dissolves.

Give each student an task sheet.

Students will describe their speculative design, record their observations, and answer questions about the task on the activity sheet. The describe It with Atoms & Molecules and also Take It additional sections the the activity sheet will either be completed together a class, in groups, or individually, depending upon your instructions. Look in ~ the teacher version of the activity sheet to find the questions and answers.

Have college student groups talk about the complying with questions:

How can you investigate even if it is the temperature of water affect the amount of coating that dissolves indigenous an M&M? What are the variables in this experiment, and how will you manage them?

As girlfriend visit the groups and listen to their discussions, check to watch if students room thinking around variables such as:

Kind of containerAmount that water color of the M&M’sWhen the M&M’s are inserted in the waterLocation the the M&M’s in each cup

All this variables should be preserved the same. Students need to realize the the just variable that have to be readjusted is the temperature of the water.

Have student teams share their principles for comparing the result of temperature on dissolving and consider exactly how each plan controls variables.

As each team presents their plans, have the course identify how each plan controls variables. Some groups may have planned to test M&M’s in hot and cold water but didn’t think about using room-temperature water, too. Encourage all groups to check an M&M in all 3 temperatures of water. The room-temperature water serves as a control and can help students view the distinction in just how temperature affect dissolving.

Explore

Have groups place one M&M in cold, room-temperature, and also hot water in ~ the same time to investigate the impact of temperature top top dissolving.

Question to Investigate

Does the temperature of water impact the quantity of coating that dissolves native an M&M?

Materials because that Each Group

3 same-colored M&M’s 3 clear plastic cups1 paper of white paperRoom-temperature waterHot water (about 50 °C)Cold water (about 5 °C)

Procedure

Pour cold, room-temperature, and also hot water right into the cups so that the water is deep enough to sheathe an M&M. Place the three cups ~ above the white paper. Create Cold, Room-temp, and also Hot close to its cup.

With the assist of her partners, place a same-colored M&M in the center of each cup in ~ the very same time. Observe for about 1 minute.

*

Expected Results

More color and sugar dissolve from the M&M in the hot water and less in the room-temperature and also cold water. This method there is more chocolate visible on the M&M in the warm water than there is in the room-temperature and cold water. The color and sugar in the room-temperature water dissolve somewhere between the cold and hot water, but are much more similar come the cold 보다 the hot.

Note: There space actually two procedures happening in this activity. The color and also sugar space dissolving in the water yet they are also diffusing in the water. The temperature that the water affects the quantity of dissolving but it additionally affects the rate of diffusion. College student should emphasis on the surface of the M&M to judge the lot of color and also sugar the dissolves.

Record and discuss college student observations.

Ask students:

Does the temperature of the water impact the quantity of colored coating the dissolves from an M&M? exactly how do girlfriend know? based upon their observations, students must conclude the the hot water causes an ext dissolving. College student may have actually noticed a greater difference in the quantity of dissolving in between the hot and also the room-temperature water than between the room-temperature and the cold water. If nobody comments top top this, suggest that over there is a difference.Explain

Discuss how differences in molecular motion caused more of the street coating to dissolve in warm than in cold water.

Ask students:

What are the differences in the way water molecules relocate in cold, room-temperature, and also hot water?Students should remember the water molecules move quicker in hot water 보다 in cold. Why carry out you think sugar dissolves far better in warm water 보다 in cold water?The factor why sugar dissolves in ~ a quicker rate in warm water needs to do with increased molecular motion. The included energy in the hot water causes water molecule to move faster and sucrose molecules to vibrate faster. This added movement has tendency to make the bonds between sucrose molecules easier to overcome. As soon as faster-moving water molecules affix to sucrose molecules, a higher proportion of this sucrose-water interactions have enough power to pull sucrose molecules away from various other sucrose molecules, therefore the price of dissolve increases.Why do you think there is a greater distinction in the lot of dissolving between the hot and room-temperature water than in between the room-temperature and cold water?There is a greater distinction in the rate of dissolving since there is a greater difference in temperature between hot and also room-temperature water (about 30 degrees) than between room-temperature and cold water (about 15 degrees). Explore

Either carry out a demonstrate or present a video clip to inspection whether every substances dissolve much better in hot water 보다 in cold water.

Ask student to do a prediction:

In the activity, you have actually seen that hot water dissolves sugar better than cold water. Do you think the salt will dissolve much better in warm water 보다 in cold, prefer sugar does?

Project the image Hot and Cold Water Dissolve Salt vs. Sugar.

If you select to execute the demonstration, follow the procedure below.

Question come Investigate

Will salt dissolve much far better in warm water than in cold, prefer sugar does?

Materials for the Demonstration

4 i graduated cylinders (50 or 100 mL)Hot water (about 50 °C)Cold water (about 5 °C)SaltSugarTablespoon4 tiny cups

Teacher Preparation

Label two tiny cups salt and two cup sugar. Location 1 tablespoon of salt and also 1 tablespoon of street in every of their labeled cups.

Procedure

Salt in Hot and also Cold WaterPlace 25 mL of warm water and 25 mL of cold water in two separate graduated cylinders. At the exact same time, to water one tablespoon the salt into each graduated cylinder. Perform not swirl, shake, or stir. Set these graduated cylinders aside.Sugar in Hot and Cold WaterPlace 25 mL of hot water and also 25 mL the cold water in two different graduated cylinders.

At the very same time, pour one tablespoon that sugar right into each i graduated cylinder. Do not swirl, shake, or stir. Set these graduated cylinders aside.

*
Compare the quantities of salt and sugar left undissolvedShow students the graduated cylinders v the salt. Show students the i graduated cylinders v the sugar.

Expected Results

Less street is visible in the warm water 보다 in the cold, an interpretation that an ext sugar disappear in the hot water 보다 in the cold water. Over there is no evident difference between the lot of salt the dissolves in the hot water contrasted to the cold water. This mirrors that temperature affect the dissolving of sugar much more than that affects the dissolving of salt.

Extend

Plot a solubility curve because that potassium chloride and also compare it to the solubility of sugar and salt.

See more: How Much Does A Sandbag Weight, Sandbaggy Burlap Sand Bag

Tell students the they will certainly plot the solubility of potassium chloride on a graph detailed on the activity sheet. Define that potassium chloride is supplied as a salt instead of for world who have to not eat consistent salt (sodium chloride.)

Table 2. Solubility the Potassium Chloride in Water from 0–100 °C.Temperature (° C)Potassium Chloride
020406080100
283338445055
*

Ask students:

At what temperature would certainly you say the the solubility of salt chloride and also potassium chloride are around the same?At 0 °C, which substance is the least soluble? in ~ 0 °C, which substance is the many soluble?