🥶 Salt and freezing time: the whole packet

🥶 Salt and freezing time · 4th–8th grade · 1 day of testing · free · 240 minutes a sitting

My days, if the fair is 14 days away

Count back from your fair day and write in each date. Fewer days than this? The jobs share days, in this order; nothing is skipped.

Dates from my teacher

• My question is due
• Testing starts
• My results table and graph are due
• My board is due

In this packet

1. 🗓️ My project plan
2. 💭 My hypothesis
3. 🧺 Change, measure, keep the same
4. 🪜 My steps
5. 📊 My results
6. 📓 My logbook
7. ✅ My conclusion
8. ✂️ Board titles to cut out
9. 🏅 The judge's questions and my certificate

If I change how much salt is in the water, then how long the water takes to freeze all the way through will ________________, because _____________________________________________

What I think will happen, in my own words:

4 levels × 3 tries at each = 12 tries in all. If anything you keep the same changes, you won't know which change made the difference.

What I need

• 🥛 Clear plastic cups, all the same size: 12, the same size
• 🚰 Water from the tap
• 🧂 Salt
• 🥛 A measuring cup
• 🥄 Measuring spoons
• 🥄 A spoon
• 🍽️ A baking tray or big plate
• ⏱️ A stopwatch or a kitchen timer
• 🩹 Masking tape, to mark lines

Be safe: 💧 Water

1. Label twelve clear cups with tape: three each for no salt, a quarter teaspoon, half a teaspoon and 1 teaspoon.
2. Pour a quarter cup of tap water into every cup.
3. Stir the right amount of salt into each salty cup until it disappears. Never drink the salty water.
4. Stand all twelve cups on a tray, spaced apart, and slide the tray into the freezer.
5. Start the timer. Every 30 minutes, take the tray out for a moment and press a spoon into the middle of each cup.
6. A cup is frozen all the way through when the spoon will not push in.
7. Write the minutes when each cup was first frozen all the way through.
8. If a cup is still runny at 240 minutes, write 240.
9. Find the mean time for each amount of salt, and draw a line graph with salt along the bottom.

Write each number in your results table the moment you measure it.

I changed: Salt in a quarter cup of water   I measured: how long the water takes to freeze all the way through (minutes)

MY GRAPH (a line graph: salt in a quarter cup of water along the bottom, minutes up the side)

What I noticed: ______________________________________________

Write something every day you work on it, even the days you only gather things. More days? The three-page logbook prints from peabody.kids/science-fair/templates/logbook.

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: swap the salt for sugar, spoon for spoon, and draw both lines on one graph.

1. What made you want to ask this question? Say something like: I wanted to know: does salty water take longer to freeze?
2. What did you think would happen, and why? Say something like: I thought changing how much salt is in the water would change how long the water takes to freeze all the way through, and I wrote down why.
3. What did you change, and what did you measure? Say something like: I changed how much salt is in the water (No salt, A quarter teaspoon, Half a teaspoon, 1 teaspoon) and measured how long the water takes to freeze all the way through in minutes.
4. What did you keep the same, and why does that matter? Say something like: I kept a quarter cup of water in every cup and the same kind of cup the same, so only how much salt is in the water was different.
5. How many times did you test it? Say something like: 3 times at each of my 4 levels, and I found the middle number.
6. What did you find out? Show me in your numbers. Say something like: Look at my table: No salt and 1 teaspoon gave different numbers, and here's the pattern.
7. Was your hypothesis right? How do you know? Say something like: My numbers show whether I was right, partly right or not, and I can show you where.
8. Did anything go wrong, or surprise you? Say something like: One try was odd, so I did it again and wrote it in my logbook.
9. If you did it again, what would you change or test next? Say something like: I'd change a second thing: swap the salt for sugar, spoon for spoon, and draw both lines on one graph.