Grade 5 (age 10-11)

Dissolving and Solutions

Stir sugar into water and it vanishes, becoming sugar water. This is dissolving: a solute (sugar) spreads through a solvent (water) to form a solution. Add too much and it stops, but stirring, crushing, or heating speeds it up. Use the sliders to change the sugar amount and concentration and watch.

What does dissolving mean?

Sugar amount40g

🧊 What is dissolving?

①Dissolving: a solute mixes evenly into a solvent

②Solution: liquid formed when solute dissolves in solvent

③Sugar water = sugar (solute) + water (solvent)

④Too much solute and it stops dissolving (saturated)

Concentration of a Solution

Concentration50

🔬 Concentrated vs. Dilute

①Lots of sugar in same water → concentrated

②Little sugar → dilute

③Concentrated sugar water tastes sweeter

④Concentrated salt water makes an egg float!

Speeding Up Dissolving

Faster Dissolving

Stir + crush + heat

Three ways to dissolve more quickly

💡 Why does it dissolve faster?

①Stirring: solute meets solvent more

②Breaking small: more surface area

③Heating: molecules move faster

④Powder sugar dissolves faster than a sugar cube!

Summary

Core Concept

Solution = solute (dissolves) + solvent (dissolves it)

Dissolving = solute mixes evenly into solvent

🎯 Key Points

①Solute: substance that dissolves (sugar, salt)

②Solvent: liquid that dissolves it (water)

③Solution: solute + solvent mixed evenly

④Saturated: no more can dissolve

⑤Stir, crush, heat — to dissolve faster

Examples and Unit Test

Example 1

In sugar water, which is the substance that dissolves (solute) and which is the liquid that dissolves it (solvent)?

Dissolving is one substance mixing evenly into a liquid.

In sugar water, the sugar that dissolves is the solute and the water is the solvent.

▸ Solute: sugar / solvent: water

Solution = solute + solvent. Sugar water is sugar (solute) dissolved in water (solvent).

Example 2

What are three ways to dissolve a sugar cube in water faster?

Stirring makes the solute and solvent meet more often, so it dissolves faster.

Crushing it increases the surface area, and warming the water makes molecules more active; both speed up dissolving.

▸ Stir, crush into smaller pieces, raise the water temperature

All three help the solute mix with the solvent, speeding up dissolving.

Unit-test style

Which statement about dissolving and solutions is correct?

①The solute is the liquid that dissolves other substances

②Warming the water makes sugar dissolve faster

③Crushing the solute makes it dissolve more slowly

④A concentrated solution has less solute than a dilute one

⑤A saturated solution can dissolve even more solute

▸ ② Warming the water makes sugar dissolve faster

The higher the temperature, the more active the molecules, so dissolving is faster.

The solute is the substance that dissolves (①), crushing makes it faster (③), a concentrated solution has more solute (④), and a saturated solution dissolves no more (⑤).

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Temperature & Heat

Acid-Base Indicator