Lesson 2 of 6 · Reaction Rates
Experiment⭐ 30 XP🧪 Potion KitchenConcentration, Pressure and Rate
Reaction Rates.
🎯 Your mission
Predict it first. Then prove yourself right (or wrong).
⚡ The twist
Mixing two safe things doesn't always make a safe thing.
Mind = Blown
💧 Hot water can freeze faster than cold water under the right conditions. Nobody fully understands why.
Make a hypothesis first
Predict: will the mixture get hotter, colder, or stay the same?
What You'll Learn
Raising concentration packs more particles into the same volume, so collisions happen more often and the rate rises. For gases the equivalent lever is pressure. Neither changes the proportion of collisions that succeed — only how many occur.
Key Words
Tap a word to see its definition.
Materials Needed
- sodium thiosulfate solution
- dilute hydrochloric acid
- conical flasks
- printed cross
- stopwatch
- measuring cylinders
Safety First
- This reaction releases sulfur dioxide — work in a well-ventilated room or fume cupboard, and keep anyone with asthma away.
- Goggles throughout; dispose of the cloudy mixture as directed.
Steps
Read the explanation above and note the two key terms before you start.
React sodium thiosulfate with hydrochloric acid at five concentrations, timing how long the cross under the flask takes to disappear. Plot 1/time against concentration and describe the relationship.
Record what actually happened, including anything that did not match what you expected.
Write a conclusion that answers the question this lesson opened with, and state your uncertainty.
Check Your Understanding
Question 1
1 of 2Increasing the concentration of a reactant increases the rate because:
Where you see this in real life
Your toothpaste, your soap, even your breakfast involves this.
Stretch Challenge
Try this in real life this week.
Ask a grown-up to help you mix two safe kitchen things. Predict what will happen first.
For the dinner table
“What's something we cook that mixes things together this way?”
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Concentration, Pressure and Rate
Predict it first. Then prove yourself right (or wrong).
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