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Effects Of Heat Energy
- 1. Effects of HeatEnergy Pages 118 to 125
- 2. Think, pair, shareWhy you think that there are gaps in between the railway track?
- 3. Objectives 1 Statethe forces of expansion and contraction in solids State examples and applications of heat energy in solids
- 4. Heat Energy Objectsheated – Size increase, EXPANSION Objects cooled – Size decrease, CONTRACTION Expansion and contraction occurs in all 3 states of matter – solid, liquid and gas
- 5. Effect of heatenergy - Solid Expansion and contraction of solids are so small Different metals expand and contract at different times and by different amounts Examples Railway tracks will expand on hot days if no gap very dangerous, train can derail and endanger passengers Bridges have fitted rollers to allow for expansion and contraction, allow bridge to slide over them smoothly when expanded Overhead cables and telephone lines expand during hot and contract and become taut on cold days. Hang loosely.
- 6. Effect of heatenergy - Solid Examples Concrete surfaces such as road and paths expand when heated, small gaps found every few meters in the concrete roads and paths Pipes carrying water or steam are looped at intervals to allow for expansion. If not the pipes will burst
- 7. Applications of heatenergy - Solid Rivets are used to join two steel plates together. Hot rivet is driven through the hole in the plates. One end of the rivet is hammered to form a new rivet head. When cool, the rivet will contract and held the two plates tightly together http://www.bbc.co.uk/schools/ks3bitesize/science/chemistry/particle_model_5.shtml
- 8. Applications of heatenergy - Solid Bimetallic strips made up of two different metal, steel/iron and brass Hotter bend downwards, colder bend upwards Both metals expand and contract by different amounts. Brass expands and contracts more than steel
- 9. Applications of heatenergy - Solid Bimetallic strips is use in thermostats in refrigerators, ovens, irons and heaters Regulate the temperature of these appliances It is also used in fire alarms, when the strip gets hot, it bends and completes an electrical circuit. A bell in the circuit rings to warn of a fire
- 10. Review Questions DoCheckpoint Question 1 pg 120 Do Inquiry time Question 1 pg 121 Do Checkpoint Question 2 pg 122
- 11. Objectives 2 Statethe forces of expansion and contraction in liquids State examples and applications of heat energy in liquids
- 12. Effect of heatenergy - Liquid Almost all liquids expand when heated and contract when cooled Drink factories need to allow space when filling up their bottles or cans No allowance will caused the bottles or cans to burst
- 13. Application of heatenergy - Liquid Liquid in glass thermometer Mercury or alcohol thermometers Thermometer is filled with mercury or alcohol in the bulb When in contact with cold substances mercury/alcohol will contract and the mercury/alcohol thread will drop When in contact with hot substances mercury/alcohol will expand and causing the mercury/alcohol thread to rise
- 14. Unique quality ofwater Water expand when it is being cooled from 4 ˚ C to 0 ˚ C Starts to contract when heated from 0 ˚ C to 4 ˚ C It reaches its minimum volume and maximum density at 4 ˚ C
- 15. Objectives 3 Statethe forces of expansion and contraction in gases State examples and applications of heat energy in gases
- 16. Effect of heatenergy - Gases Gases expand when heated and contract when cooled Gases expand and contract much more than solids and liquids of the same volume for the same change in temperature
- 17. Effect of heatenergy - Gases Example, we should not pump car tyres to the maximum pressure on hot days – may burst
- 18. Application of heatenergy - Gases Hot balloon uses the expansion of gases Filled with heated air As volume of air increases (expansion), the density of air decreases Warm air less dense this it rises and carries the balloon upwards
- 19. Application of heatenergy - Gases Baking bread or cake, baking powder is added Carbon dioxide gas is released from the baking powder expands Causing the dough to rise
- 20. Review Questions DoCheckpoint Question 2 pg 120 Do Checkpoint Question 3 pg 122
- 21. Objectives 4 Explainusing a particulate model for expansion and contraction
- 22. Expansion and ContractionWhen substances expand or contract, the particles stay the same size Only the spaces between the particles changes The particles in the solid vibrate more when it is heated thus take up more room - EXPANSION Similar to liquid and gases when heated
- 23. Expansion and ContractionThe particles in solid will vibrate less when it is cold thus take up less space – CONTRACTION Similar to liquid and gases when cooled
- 24. Review Questions (page125) Do it now!