Does warm water hold more salt than cold?
- 💧 Water
My hypothesis
If I change how warm the water is, then how many teaspoons of salt dissolve in the water will ______, because ______.
You fill in the blanks. Think about whether warm water holds more of something, or only dissolves it faster. A guess is a good because: the test finds out.
Change, measure, keep the same
CHANGE
how warm the water is: Cold from the fridge, Room temperature, Warm from the tap
MEASURE
how many teaspoons of salt dissolve in the water, in teaspoons
KEEP THE SAME
- a quarter cup of water in every cup
- salt added half a teaspoon at a time
- stirring the same way, for a full minute each time
Scientists call the thing you change the independent variable and the thing you measure the dependent variable. The things you keep the same are the controls: if one of them changed too, you wouldn't know which change made the difference. Try each of the 3 levels 3 times.
What you need
- Salt: about a cup
- Cold water from the fridge
- Water from the tap: left out for an hour, for room temperature
- Warm water: warm from the tap, never hot
- Clear plastic cups, all the same size: 3
- A measuring cup
- Measuring spoons
- A spoon
- A thermometer (digital, or the red-liquid kind)
- A stopwatch or a kitchen timer
Steps
- Pour a quarter cup each of cold, room-temperature and warm tap water into three clear cups.
- Read each cup's temperature with the thermometer and write it down.
- Stir half a teaspoon of salt into the cold cup for 30 seconds. Never drink the salty water.
- If all the salt is gone, add another half teaspoon and stir again.
- Stop when some salt is still on the bottom after one minute of stirring.
- Count the teaspoons that dissolved. Leave out the last half teaspoon, the one that stayed.
- Do the same with the room-temperature cup and the warm cup, stirring the same way.
- Pour out, rinse the cups, and do the whole test two more times with fresh water.
- Find the mean for each temperature, and draw a bar graph.
Every step is one you can do yourself, with a grown-up nearby. Write each number down straight away, in the table below, so nothing is lost.
Your results table
Name ______________________ Fair day ____________
Question: Does warm water hold more salt than cold?
I changed: Water I measured: how many teaspoons of salt dissolve in the water (teaspoons)
| Water | Try 1 (teaspoons) | Try 2 (teaspoons) | Try 3 (teaspoons) | Mean |
|---|---|---|---|---|
| Cold from the fridge | ||||
| Room temperature | ||||
| Warm from the tap |
MY GRAPH (a bar graph: water along the bottom, teaspoons up the side)
What I noticed: ______________________________________________
From 4th grade, add the tries for each level and divide by how many there were: that's the mean, and it goes in the last column. Then draw a bar graph, one bar for each thing you tried.
Name ______________________ Fair day ____________
Question: Does warm water hold more salt than cold?
If I change how warm the water is, then how many teaspoons of salt dissolve in the water will ________________, because _____________________________________________
| I CHANGE | I MEASURE | I KEEP THE SAME |
|---|---|---|
| Water: Cold from the fridge, Room temperature, Warm from the tap | how many teaspoons of salt dissolve in the water (teaspoons) |
|
What I think will happen, in my own words:
Name ______________________ Fair day ____________
Question: Does warm water hold more salt than cold?
| Date | What I did | What I saw | What I think |
|---|---|---|---|
Name ______________________ Fair day ____________
Question: Does warm water hold more salt than cold?
| Date | What I did | What I saw | What I think |
|---|---|---|---|
Name ______________________ Fair day ____________
Question: Does warm water hold more salt than cold?
| Date | What I did | What I saw | What I think |
|---|---|---|---|
Name ______________________ Fair day ____________
Question: Does warm water hold more salt than cold?
My hypothesis was ☐ right ☐ partly right ☐ not right.
I know because my numbers show:
What surprised me, or what might have gone wrong (7th and up):
Next time I would test:
Idea: Change a second thing: repeat the test with sugar, and graph salt and sugar side by side at each temperature.
Why it works
Water can only hold so much salt, and after that the extra just sits at the bottom. For salt, warm water holds only a tiny bit more than cold water, so your three cups may end up very close. Sugar is different: warm water holds noticeably more of it.
Going further (7th and up): Change a second thing: repeat the test with sugar, and graph salt and sugar side by side at each temperature.
Board layout
- ❓ Question (10 × 8 in): Does warm water hold more salt than cold?
- 💭 Hypothesis (10 × 9 in): If I change how warm the water is, then how many teaspoons of salt dissolve in the water will ______, because ______.
- 🧺 Materials (10 × 12 in): 10 things: see your list.
- 🪜 Steps (22 × 9 in): 9 steps, three tries at each level.
- 📊 Results (22 × 16 in): Your table (Water down the side, tries across) and your bar graph.
- ✅ Conclusion (10 × 14 in): My hypothesis was right / partly right / not right. I know because…
Materials to list: Salt; Cold water from the fridge; Water from the tap; Warm water; Clear plastic cups, all the same size; A measuring cup; Measuring spoons; A spoon; A thermometer (digital, or the red-liquid kind); A stopwatch or a kitchen timer.
Bring photos or drawings of your test. Nothing wet, hot, powered or alive on the table.
This project at your grade
| 4th–6th grade | Tries: three at each level. The table: units in the header and a mean column. The graph: a bar graph, or a line for a number that grows. The conclusion: right, partly or not, and the numbers that show it. |
|---|---|
| 7th grade and up | Tries: three or more at each level. The table: a mean for every level of both tests. The graph: a graph with two lines or two sets of bars. The conclusion: the numbers, what might have gone wrong, and a next question. Second variable: repeat the test with sugar, and graph salt and sugar side by side at each temperature. |
Every grade this project fits works out a mean. See every project for 5th grade, or print a blank results table.
What a judge will ask
- What did you change, and what did you measure? I changed how warm the water is and measured how many teaspoons of salt dissolve in the water, in teaspoons.
- What did you keep the same, and why does that matter? I kept a quarter cup of water in every cup and salt added half a teaspoon at a time the same, so the only difference was how warm the water is.
- How many times did you test it? 3 times at each of my 3 levels.
- If you did it again, what would you change or test next? I'd repeat the test with sugar, and graph salt and sugar side by side at each temperature.
Make it yours
Keep this project on this device and Peabody counts down to your fair day, with a plan for each day. Nothing is sent anywhere.
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