Mixing substances of different temperatures
Lesson details
Learning outcome
I can predict the resulting temperature when two substances of different temperatures are put together.
Key learning points
- Mixing hot water with cold water results in water cooler than the hot water and warmer than the cold.
- When hot and cold water are mixed, the temperature is closer to that of the water there was more of.
- A cold object placed in hot water makes the water particles move more slowly and those in the object move more quickly.
- A hot object placed in cold water makes the water particles move more quickly and those in the object move more slowly.
Keywords
Volume - the amount of space an object takes up
Particle model - the idea that all objects are made of tiny particles that are in constant motion
Temperature - the higher the temperature of an object, the faster its particles move and the hotter it is
Collide - when two objects bump into each other
Common misconception
When samples of water are added at different temperatures, some pupils add or subtract the temperatures, applying a mathematical process without appearing to think about what is happening.
Ask pupils to predict changes to the resulting temperature using water at a range of starting temperatures and then demonstrate each one, measuring the temperature of the resultant mixture each time.
Teacher tip
Marbles shaken in a tray can be useful model for a liquid, but their (relative) spacing must be made greater than it would be in a liquid to give the marbles space to move and collide. Emphasise the fact that particles in a real liquid are much closer together.
Content guidance
Risk assessment required - equipment
Supervision
Adult supervision required
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.A rectangular block of steel has a length of 8 cm, a width of 4 cm and a height of 3 cm. What is the volume of the block in cm³?
Q2.Which of the following pieces of equipment can measure the volume of a liquid most precisely?
Q3.In which state of matter do the particles in water move the fastest?
Q4.How close together are the particles of a liquid?
Q5.What happens to the particles that make up a gas when it is heated to a higher temperature?
Q6.Why would touching a very hot piece of solid metal burn your skin?
Assessment exit quiz
6 Questions
Q1.50 cm³ of water at 80°C is mixed with 50 cm³ of water at 40°C. What will be the resulting temperature of the mixture?
Q2.100 cm³ of water at 60°C is mixed with 50 cm³ of water at 30°C. What will be the resulting temperature of the mixture?
Q3.100 cm³ of water at 80°C is mixed with 300 cm³ of water at 40°C. What will be the resulting temperature of the mixture?
Q4.What word describes the directions in which particles of water move in the liquid or gas state?
Q5.What happens when faster moving particles of a hot solid collide with slower moving particles of a cold liquid?
Q6.Why does a cube of solid water (ice) melt when it is put into a glass of lemonade at room temperature?
To help you plan your 7 science lesson on: Mixing substances of different temperatures, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 7 science lesson on: Mixing substances of different temperatures, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
Our video is a tool for planning, showing how other teachers might teach the lesson, offering helpful tips, modelled explanations and inspiration for your own delivery in the classroom. Plus, you can set it as homework or revision for pupils and keep their learning on track by sharing an online pupil version of this lesson.
Explore more key stage 3 science lessons from the Heating and cooling unit, dive into the full secondary science curriculum, or learn more about lesson planning.