Which makes ice water colder: salt or sugar?
- 💧 Water
- 🚫 Test food is not for eating
My hypothesis
If I change what is stirred into the ice water, then how cold the ice water gets after 10 minutes will ______, because ______.
You fill in the blanks. Think about what happens when something dissolves in the water around the ice. A guess is a good because: the test finds out.
Change, measure, keep the same
CHANGE
what is stirred into the ice water: Nothing, Sugar, Salt
MEASURE
how cold the ice water gets after 10 minutes, in degrees
KEEP THE SAME
- two tablespoons in every cup that gets something
- six ice cubes and half a cup of cold water in every cup
- the same kind of cup
- ten stirs every two minutes
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
- Ice cubes, all from the same tray: 18 cubes for each round
- Clear plastic cups, all the same size: 3, the same size
- Cold water from the fridge: half a cup for each cup
- A measuring cup
- Salt: 2 tablespoons for each round
- Sugar: 2 tablespoons for each round
- Measuring spoons
- A spoon
- A thermometer (digital, or the red-liquid kind)
- A stopwatch or a kitchen timer
- Masking tape, to mark lines
Steps
- Label three cups with tape: nothing, sugar and salt.
- Put six ice cubes and half a cup of cold water in each cup.
- Stir two tablespoons of sugar into the sugar cup and two of salt into the salt cup.
- Start the timer, and stir each cup ten times every two minutes.
- At 10 minutes, hold the thermometer in each cup for 30 seconds, then read it.
- Write the three temperatures in your table, rinsing the thermometer between cups.
- Pour everything away and do it twice more with fresh ice.
- Draw a bar graph with one bar for each cup.
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: Which makes ice water colder: salt or sugar?
I changed: What goes in I measured: how cold the ice water gets after 10 minutes (degrees)
| What goes in | Try 1 (degrees) | Try 2 (degrees) | Try 3 (degrees) | Mean |
|---|---|---|---|---|
| Nothing | ||||
| Sugar | ||||
| Salt |
MY GRAPH (a bar graph: what goes in along the bottom, degrees 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: Which makes ice water colder: salt or sugar?
If I change what is stirred into the ice water, then how cold the ice water gets after 10 minutes will ________________, because _____________________________________________
| I CHANGE | I MEASURE | I KEEP THE SAME |
|---|---|---|
| What goes in: Nothing, Sugar, Salt | how cold the ice water gets after 10 minutes (degrees) |
|
What I think will happen, in my own words:
Name ______________________ Fair day ____________
Question: Which makes ice water colder: salt or sugar?
| Date | What I did | What I saw | What I think |
|---|---|---|---|
Name ______________________ Fair day ____________
Question: Which makes ice water colder: salt or sugar?
| Date | What I did | What I saw | What I think |
|---|---|---|---|
Name ______________________ Fair day ____________
Question: Which makes ice water colder: salt or sugar?
| Date | What I did | What I saw | What I think |
|---|---|---|---|
Name ______________________ Fair day ____________
Question: Which makes ice water colder: salt or sugar?
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: try one, two and three tablespoons of each, and graph a line for salt and a line for sugar.
Why it works
Anything that dissolves in water lowers the temperature at which it freezes, so sugar and salt can both make ice water colder than plain ice water. Spoon for spoon, salt puts far more tiny pieces into the water than sugar does, and the number of pieces is what matters, so salt usually makes the bigger change.
Going further (7th and up): Change a second thing: try one, two and three tablespoons of each, and graph a line for salt and a line for sugar.
Board layout
- ❓ Question (10 × 8 in): Which makes ice water colder: salt or sugar?
- 💭 Hypothesis (10 × 9 in): If I change what is stirred into the ice water, then how cold the ice water gets after 10 minutes will ______, because ______.
- 🧺 Materials (10 × 12 in): 11 things: see your list.
- 🪜 Steps (22 × 9 in): 8 steps, three tries at each level.
- 📊 Results (22 × 16 in): Your table (What goes in 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: Ice cubes, all from the same tray; Clear plastic cups, all the same size; Cold water from the fridge; A measuring cup; Salt; Sugar; Measuring spoons; A spoon; A thermometer (digital, or the red-liquid kind); A stopwatch or a kitchen timer; Masking tape, to mark lines.
Bring photos or drawings of your test. Nothing wet, hot, powered or alive on the table.
This project at your grade
| 1st–3rd grade | Tries: three at each level (one is fine at a first fair). The table: levels and tries, numbers or pictures. The graph: a picture, or a simple bar graph. The conclusion: what happened, in their words. |
|---|---|
| 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. |
From 4th grade up, the table gets a mean column. See every project for 2nd grade, or print a blank results table.
What a judge will ask
- What did you change, and what did you measure? I changed what is stirred into the ice water and measured how cold the ice water gets after 10 minutes, in degrees.
- What did you keep the same, and why does that matter? I kept two tablespoons in every cup that gets something and six ice cubes and half a cup of cold water in every cup the same, so the only difference was what is stirred into the ice water.
- 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 try one, two and three tablespoons of each, and graph a line for salt and a line for sugar.
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.
Try next
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