October 5 A. Bell Work B. Have 4.2 Notes I Out for a stamp C. Today we will work on 4.2 Notes II D. Homework: 4.2 Notes II (due tomorrow end of

Transcription

1 October 5 A. Bell Work B. Have 4.2 Notes I Out for a stamp C. Today we will work on 4.2 Notes II D. Homework: 4.2 Notes II (due tomorrow end of class) Read 4.3 and take notes (due Monday)

2 4.2 Key Concept: Energy Flows from warmer to cooler objects

3 In Your 4.2 Notes II Create a small section titled Heat Transfer Demo Draw the Set Up Describe Result

4 Demo: Feeling Heat Transfer 1. Place one hand in the cold water and the other hand in the hot water. 2. Wait 20 seconds 3. Move both hands to the room temp water

5 Demo: Feeling Heat Transfer In your Notes Describe the Result: Which hand gains thermal energy from the room temp water? Which hand gives thermal energy to the room temp water?

6 Demo: Feeling Heat Transfer In your Notes Describe the Result: Which hand gains thermal energy from the room temp water? Cold hand Which hand gives thermal energy to the room temp water? Warm hand

7 Heat: The flow of energy from an object at a higher temp to an object at a lower temp

8 E E E E E E E E Warm Object Cold Object Energy moves from warm cold

9 E E E E E E E E Warm Object Cold Object Thermal Energy moves from warm cold We call this transfer heat

10 Heat vs. Temperature Heat is the flow of energy, temperature is a measure of it

11 Cold is not a Thing Get lots of $ = rich Lose your $ = poor I cannot give you poor. I can only transfer money

12 Cold is not a Thing Get thermal energy = hot Lose thermal energy = cold I cannot give you cold. I can only transfer thermal energy. The transfer is called heat

13 Cold is not a Thing We don t keep out the cold But we can try to keep thermal energy from leaving

14 Iron & Water Demo Draw this set up, leave room to write an explanation next to it Hot Iron Cold Water

15 Iron & Water Demo In your Notes show or explain 1. How thermal energy was transferred 2. How the temperature of the Iron changed 3. How the temperature of the water changed Hot Iron Cold Water

16 -and-thermodynamics

17 Iron & Water Demo In your Notes show or explain 1. How thermal energy was transferred iron to water 2. How the temperature of the Iron changed iron decreased temp 3. How the temperature of the water changed water increased temp Hot Iron Cold Water

18 Thermal Energy: The energy an object has due to the motion of its particles. The total KE of an object s particles * We cannot calculate an exact number for thermal energy but we can infer its relative magnitude

19 Temperature vs. Thermal Energy Temperature = Average KE Describes the average movement of a particle in that substance Thermal Energy = Total KE Describes the total movement of all the particles combined

20 Lake vs. Cup of Water (an example of Temperature vs. Thermal Energy)

21 Imagine I scoop a cup of water from the lake. The cup of water and the lake water are the same temperature. 1. Which one has more thermal energy? 2. Why?

22 Imagine I scoop a cup of water from the lake. The cup of water and the lake water are the same temperature. 1. Which one has more thermal energy? 2. Why? More mass means more particles. More TOTAL Kinetic Energy

23 Match vs. Iceberg Which has higher temperature? Which has more thermal energy? You can t melt an iceberg with a match

24 Match vs. Iceberg Which has higher temperature? the match. Particles are moving faster, have greater average KE Which has more thermal energy? the iceberg. Particles move slowly but there are more of them! So the total KE is much greater than that of the match.

25 Heat can be measured When we want to know how much chemical energy is in food we burn the food and measure the heat (energy flow) that results

26 calorie: the amount of energy needed to raise the temp of 1g of water by 1 degree Celsius a special machine that measures the thermal energy release of food

27 calorie: the amount of energy needed to raise the temp of 1g of water by 1 degree Celsius In U.S. our calorie is actually a kilocalorie (kcal)

28 Joule: the standard scientific unit in which energy is measured 1 calorie = 4.18 Joules Some countries use Joules on food labels instead of calories

29 Some substances change temperature more easily than others