Monday, October 1, 2007

Energy in Food: Day 2

Bellwork:
1) We get energy from __________.
2) We ______________ the cheese ball to show it has energy.
3) Certain foods might have more energy than others because _______________.

Review:
- Heat is energy.
- Food has energy.
- We burned the cheese ball to prove that food has energy AND to measure how much energy there is in the cheese ball
- We will finish the "Measuring Food Energy" worksheet on workbook page 53

Calories
- One calorie is the amount of heat it takes to raise the temperature of 1 mL of water by 1°C
- 1) If we multiply the volume of water we used by the temperature change caused by the burning cheese ball, we get the number of calories in the cheese ball
20 mL x ____°C = __________ calories
- People measure food energy in calories - this is shown on food nutrition labels
- A middle school students needs 2000 calories a day to survive
2) If we divide the amount of calories a student needs (2000) by the number of calories in a cheese ball, we get the number of cheese balls we need to eat a day to survive
2000 calories ÷ ________ calories = ____________ cheese balls a day
- The number of cheese balls we calculated to eat a day is too low to survive on. This is because there are heat calories and food Calories. 1000 heat calories = 1 food Calorie
3) Multiplying the number of cheese balls we thought we needed (#2) by 1000, we get the number of cheese balls we actually need to eat a day to survive
__________ cheese balls x 1000 = ________________ cheese balls a day

Lecture:
- Carbohydrates (carbs, sugars) give us the most energy of any food
- Plants make carbohydrates when they make their own food