# Rate of Dissolving 1

In this worksheet, students will be helped to follow through an experiment to discover what factors affect the rate (speed) at which a solid dissolves.

Key stage:  KS 2

Curriculum topic:   Properties and Changes of Materials

Curriculum subtopic:   Dissolving and Solutions

Difficulty level:

### QUESTION 1 of 10

Luke wanted to find out whether the amount of sugar he could dissolve in water could be changed by different factors. First he tried to change how much he stirred the sugar and water mixture.

Luke set up three beakers with 100ml of water in each. He added two spoonfuls of sugar to each and stirred them at different speeds.

Here are his results:

Beaker 1 Beaker 2 Beaker 3
No. of stirs per minute 5 10 20
Time to dissolve/min 3 1.5 0.5

Let's join Luke and see what his results mean.

Here are Luke's results again:

Beaker 1 Beaker 2 Beaker 3
No. of stirs per minute 5 10 20
Time to dissolve/min 3 1.5 0.5

Looking at Luke's results what do you conclude about whether stirring affected the rate at which the sugar dissolved?

more stirs sped up dissolving

more stirs slowed down dissolving

stirring didn't affect dissolving

In this experiment Luke changed one thing and kept the others the same; what did he change?

amount of water

number of stirs

amount of sugar

Next Luke decided to see whether the amount of water he dissolved the sugar in made any difference to the amount of sugar that dissolved.

He tried three different volumes of water: 100ml, 200ml and 300ml.

Here are his results:

Beaker 1 Beaker 2 Beaker 3

Amount of water/ml

100 200 300
No. spoons sugar dissolved 8 20 35

Looking at these results what do you think that Luke wrote in his science notebook?

the amount of water I used didn't affect how much sugar dissolved

the more sugar I added the faster it dissolved

the more water I had the more sugar I could dissolve in it

In this experiment Luke changed one thing and kept the others the same; what did he change?

amount of water

temperature of the water

amount of sugar

Luke decided to try changing the temperature of the water.

He set up three beakers, each at a different temperature, and added spoonfuls of sugar until no more dissolved.

Here are his results:

Beaker 1 Beaker 2 Beaker 3
Temperature/oC 10 20 30
Amount of sugar dissolved/spoonfuls 15 36 50

What do you think that Luke learned from his results?

the temperature affects how much sugar dissolves

more sugar dissolves when there's more water

more sugar dissolves as the temperature of the water increases

In this experiment Luke changed one thing and kept the others the same; what did he change?

amount of water

amount of sugar

temperature of water

Finally Luke tried one more experiment: he got some big sugar crystals, some ordinary granulated sugar and also some finely ground-up caster sugar.

 SUGAR CRYSTALS GRANULATED SUGAR CASTER SUGAR

He added spoonfuls of each sugar to 100ml of water, stirring each one,  to see how much he could dissolve in one minute.

Here are his results:

Beaker 1 Beaker 2 Beaker 3
Type of sugar Large crystals Granulated Caster
Amount dissolved in 1 min/spoonfuls 0.5 5 12

Which of the following conclusions most closely matches the results?

the size of sugar grain changes how much sugar dissolves in water

you can dissolve more caster sugar than granulated sugar

as the crystals get smaller the sugar dissolves faster

In this experiment Luke changed one thing and kept the others the same; what did he change?

amount of sugar

type of sugar

amount of water

In science experiments like these, it's really important to try to keep everything constant and just change one thing at a time if you want to find out anything useful. What do we usually call this type of experiment?

investigation

conclusion

fair test

From his experiments Luke discovered that the dissolving of sugar is affected by raising the temperature, using more water, using smaller grains of sugar and also which other factor?

stirring it more

making it hotter

doing everything faster

• Question 1

Here are Luke's results again:

Beaker 1 Beaker 2 Beaker 3
No. of stirs per minute 5 10 20
Time to dissolve/min 3 1.5 0.5

Looking at Luke's results what do you conclude about whether stirring affected the rate at which the sugar dissolved?

more stirs sped up dissolving
EDDIE SAYS
If you look at the results you can see that the more stirs Luke gave each beaker (up to 20 stirs per minute) the faster the sugar dissolved (only 30 seconds at 20 stirs/min).
• Question 2

In this experiment Luke changed one thing and kept the others the same; what did he change?

number of stirs
EDDIE SAYS
Look back - Luke's testing whether stirring the solution more affects how fast the sugar dissolves.
• Question 3

Next Luke decided to see whether the amount of water he dissolved the sugar in made any difference to the amount of sugar that dissolved.

He tried three different volumes of water: 100ml, 200ml and 300ml.

Here are his results:

Beaker 1 Beaker 2 Beaker 3

Amount of water/ml

100 200 300
No. spoons sugar dissolved 8 20 35

Looking at these results what do you think that Luke wrote in his science notebook?

the more water I had the more sugar I could dissolve in it
EDDIE SAYS
It's clear from the results that as the volume of water increases from 100ml to 300ml, so the amount of sugar that Luke was able to dissolve in it also increases (from 8 spoons to 35 spoons). To be honest that makes sense: there's more room to fit in more sugar when there's more water.
• Question 4

In this experiment Luke changed one thing and kept the others the same; what did he change?

amount of water
EDDIE SAYS
Luke changed the volume (amount) of water from 100ml to 300ml and found that more sugar dissolved when there was more water.
• Question 5

Luke decided to try changing the temperature of the water.

He set up three beakers, each at a different temperature, and added spoonfuls of sugar until no more dissolved.

Here are his results:

Beaker 1 Beaker 2 Beaker 3
Temperature/oC 10 20 30
Amount of sugar dissolved/spoonfuls 15 36 50

What do you think that Luke learned from his results?

more sugar dissolves as the temperature of the water increases
EDDIE SAYS
If you look at Luke's chart of results you can see that as the temperature of the water increases from 10 to 30°C, so the amount of sugar he can dissolve in it increases (from 15 to 50 spoonfuls). So more sugar dissolves as the temperature increases.
• Question 6

In this experiment Luke changed one thing and kept the others the same; what did he change?

temperature of water
EDDIE SAYS
Luke was varying the temperature of the water (from 10 to 30°C), finding out that as he increased it he could dissolve more sugar in the same amount of water.
• Question 7

Finally Luke tried one more experiment: he got some big sugar crystals, some ordinary granulated sugar and also some finely ground-up caster sugar.

 SUGAR CRYSTALS GRANULATED SUGAR CASTER SUGAR

He added spoonfuls of each sugar to 100ml of water, stirring each one,  to see how much he could dissolve in one minute.

Here are his results:

Beaker 1 Beaker 2 Beaker 3
Type of sugar Large crystals Granulated Caster
Amount dissolved in 1 min/spoonfuls 0.5 5 12

Which of the following conclusions most closely matches the results?

as the crystals get smaller the sugar dissolves faster
EDDIE SAYS
If you look at Luke's results you can see that there is a change: as the size of the granules of sugar gets smaller (from big crystals through to caster sugar) he is able to dissolve more and more in his 100ml of water in one minute (from half a spoonful of big crystals through to 12 spoonfuls of caster sugar); so clearly, smaller grains dissolve faster. Why? Well, with big lumps the water can only dissolve the outside layer - it takes time to get to the inside; if that lump is crushed up into tiny grains pretty much all of it is exposed and can be dissolved at once. Makes sense really!
• Question 8

In this experiment Luke changed one thing and kept the others the same; what did he change?

type of sugar
EDDIE SAYS
Here Luke was testing whether the size of the granule of sugar affected how fast it dissolved.
• Question 9

In science experiments like these, it's really important to try to keep everything constant and just change one thing at a time if you want to find out anything useful. What do we usually call this type of experiment?

fair test
EDDIE SAYS
A 'fair test' is a fairly easy concept to understand: if Luke had wanted to see whether the temperature made a difference and had different amounts of water as well that wouldn't be 'fair'. Scientifically he'd be varying two factors and so if his results were different he wouldn't know what had caused it: the temperature or the volume of water. So, to get useful results we need to change one thing and keep the others the same; then, if there is a difference in the results we KNOW what's caused it. Easy really!
• Question 10

From his experiments Luke discovered that the dissolving of sugar is affected by raising the temperature, using more water, using smaller grains of sugar and also which other factor?

stirring it more
EDDIE SAYS
Yup, the last one's stirring: it just mixes the sugar with the water so it spreads out and dissolves more quickly.
---- OR ----

Sign up for a £1 trial so you can track and measure your child's progress on this activity.

### What is EdPlace?

We're your National Curriculum aligned online education content provider helping each child succeed in English, maths and science from year 1 to GCSE. With an EdPlace account you’ll be able to track and measure progress, helping each child achieve their best. We build confidence and attainment by personalising each child’s learning at a level that suits them.

Get started