Effects Of Heat Energy

59,515 views

Published on

2 Comments
13 Likes
Statistics
Notes
No Downloads
Views
Total views
59,515
On SlideShare
0
From Embeds
0
Number of Embeds
391
Actions
Shares
0
Downloads
719
Comments
2
Likes
13
Embeds 0
No embeds

No notes for slide

Effects Of Heat Energy

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

×