Atom Frenzy – Lesson 8 – Hot and Sticky
Students test the viscosity (or ‘runniness’ and ‘stickiness’) of very cold, room temperature and warm honey and use what they have learnt about atoms and molecules to explain their observations.
1. Introduction: Introduce Lesson 8 by indicating students will build on what they learnt in Lesson 7 and examine the viscosity of a liquid at three different temperatures. They will relate how the forces between the molecules in the liquid are affected by temperature. Then introduce the Lesson 8 learning intentions using the Atom Frenzy Lesson 8 PowerPoint.
2. Discussion – Cold honey: The teacher reviews the learnings concerning viscosity from Lesson 7. They will discuss how they measured viscosity and how they made sure their activity was a ‘fair test’ in each case.
3. Activity – Exploring effect of temperature on viscosity: Exploring the effect of temperature on viscosity: as a whole class demonstration or group activity, students take one of the liquids (e.g. honey) and investigate its viscosity when it is cold, at room temperature and warm. This is achieved by allowing a set volume of the liquid at the three different temperatures to flow through a small funnel or from a teaspoon until it stops dripping.
4. Discussion – How temperature affects viscosity: Review findings of both investigations: the flow rate of different liquids and the flow rate of the same liquid at different temperature. Then, through questioning, ask students to use the molecular model to explain why different liquids flow at different rates and also why they flow more freely when they are warmer. Encourage students to relate explanations to the strength of the electrical forces between the molecules, how much the particles are vibrating and moving when heat energy is added, and also the size of the molecules.
5. Review: Review the main things learnt about viscosity including an explanation of different flow rates and new words and write them on the class Word Wall. Introduce and prepare students for the post-test.
Students will:
- know that viscosity is a measure of the ‘runniness’ of a liquid
- with guidance, plan and conduct a scientific investigation to explore viscosity
- explain that the viscosity of liquids is affected by temperature.
- Use either liquid honey or golden syrup for this activity.
- Use squeezy containers to fill the small measuring cups or the depressions in the plastic board. If using the plastic board just use holes 1, 3 and 5.
- three labelled squeezy bottles of the same type of honey (per station)
- small, graduated plastic medicine glass (30 mL) or viscosity boards (per station)
- access to ice to make an ice/water bath to cool the honey
- access to warm water to warm the honey
- timer or tablet (per group)
- three spirit thermometers (per station)
Remind students that in last week’s lesson they examined a property of liquids called viscosity.
- Who can spell ‘viscosity’? Ask all students to attempt writing it down.
- Who can remember how we measured viscosity? How runny or sticky a liquid is – how hard it is for the liquid to flow, and we timed how long each liquid took to flow.
- How does the viscosity relate to the forces between the molecules that are in each liquid? The forces between the molecules affects how sticky liquids are and how easily they flow.
Present the learning intentions for this lesson from the Atom Frenzy Lesson 8 PowerPoint.
Review what the class learned in Lesson 7 when you talked about pouring honey or maple syrup on toast or pancakes on a cold winter morning. Remind students about the key observation that honey flows even slower when it’s cold.
In this lesson’s activity students will use the same method as in Lesson 7 to measure the viscosity of cold, room temperature and warm liquid. Students should also use the same viscosity scale to record the results:
-
- flows very easily (like water)
- flows easily (but not quite as runny as water)
- flows slowly
- flows very slowly
- hardly flows at all
We recommend viewing the final part of the activity video on the right before reading the detailed activity instructions that below.
Note: If time is short, this may be completed as a teacher demonstration in preference to a student activity.
Place three squeezy bottles of the liquid to be tested (e.g. honey) at each of three workstations:
- one sitting in an ice bath
- one on the table which will be at room temperature
- the third in a warm water bath
A thermometer should be placed in the ice bath, on the bench near the honey at room temperature and in the warm water bath.
The teacher explains what students will do at each workstation. Use an additional set of workstations if you think it is necessary.
Groups could use either Method 1 – ‘The last drop’ – or Method 2 – ‘Runny races’ to test the viscosity of their cold, room temperature and warm liquid.
As with Lesson 7, the activity will take teamwork. Make sure each team member knows their role.
When everything is ready, teams conduct the investigation.
If completed as a teacher demonstration, the teacher should manage the demonstration and use student helpers as needed.
When the three trials are completed and results have been added to a results table in students science journals, have students place all small plastic measuring cups or the viscosity boards into a bucket of warm soapy water.
In Lesson 7 students saw how different liquid foods flow: some flowed easily, like water, and others hardly flowed at all, like glucose syrup.
Then review the class’s findings for the same liquid at different temperatures.
- How easily did the cold honey flow? How long did it take to flow between cups or down the board to the line?
- How easily did your honey at room temperature flow? How long did it take to flow between cups or down the board?
- How easily did your warm honey flow? How long did it take to flow between cups or down the board?
- Did everyone get the same results?
- Now, to finish the lesson, use your knowledge about how atoms and molecules move when they are cold compared to when they are hot to explain our findings. Discuss your answers in your groups.
- Who would like to volunteer their group answer to the class?
What were the main things we learnt today?
- What is viscosity? Viscosity is a measure of how much a fluid resists flowing due to the forces between molecules.
- Why do liquids flow at different rates when the temperature is different? As temperature rises, the molecules are bouncing around faster and faster. This makes it more difficult for the electric forces between molecules to grab onto each other which means the molecules can flow around each other more easily.
If you are intending to assess students understanding of the extension material in Lessons 7 and 8, then prepare for the post-test containing Questions 1-7. Alternatively, if you have already completed the post-test containing Questions 1-6, then conclude this lesson by supplying the standalone Question 7 test.