1. Measuring Energy Changes What a great way to spend block day!

2. Let’s get some units up in here! calorie: the amount of energy you need to raise the temperature of 1g of water by 1°C. –Different from Calorie (used for food) which is actually a kilocalorie (1000 cal) Joule: 1 cal = 4.184 J Conversion Factor!!!

3. Yay Practice! Ex. Express 34.8 cal of energy in Joules. 34.8cal 4.184 J = 146 J 1 cal You do one! Express 47.3 J in calories.

4. Check It! 47.3 J 1 cal = 11.3 cal 4.184 J

5. Does It Get Harder? Maybe… Specific Heat: the amount of energy needed to raise the temperature of 1g of a substance by 1 °C. –For water, we said this was 4.184 J/g °C

6. What If I Need More than 1°C? Ex. Determine the amount of energy in joules required to raise the temperature of 7.4g of water from 29.0°C to 46.0 °C. Use Q= m∙c∙∆T: m=7.4g c water =4.184 J/g °C ∆T= (big-little) = (46.0 °C – 29.0 °C) = 17.0 °C =(7.4g) x (4.184 J/g °C) x (17 °C) = 526J

7. Yay More Practice Calculate the joules of energy required to heat 454g of water from 5.4 °C to 98.6 °C.

8. Check It! Q=m∙c∙∆T m = 454g c water = 4.184 J/g °C ∆T = (98.6 °C – 5.4 °C) = 93.2 °C = (454g) x (4.184 J/g °C) x (93.2 °C) = 1.77x10 5 J or 177,000 J