 # Unit Review Boyce.

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Unit Review Boyce

Questions 1-2 6 forms of energy 5 Sources… I say 3!
Potential energy (PE) Kinetic energy (KE) Chemical Potential Energy (CPE) Mechanical Energy (ME) Electrical Energy (EE) Radiant Energy (RE) Thermal Energy (TE) 5 Sources… I say 3! Sun (Fusion) Core (Fission) Moon (Gravity)

Questions 3-4 All life on Earth needs the Sun
Photosynthesis Food Light Heat We create “things” like light bulbs and motors to convert energy from a form we can not use into a form that we can: A light bulb converts EE into light and heat! A hydroelectric dam converts KE into EE!

Questions 5, 6,7,8 = SKIP, 9, 10 Question #5
The Law of conservation of Mass Mass can not be created or destroyed, it can only be changed into different forms The First Law of Thermodynamics Energy can not be created or destroyed; energy is transferred between source and its surroundings; energy is accounted for through heat and work! Question 9 Plants use energy from the sun (light) to make food! This is done through PHOTOSYNTHESIS! Question 10 In regards to energy, the Earth is an open system, it constantly receives and releases energy. In regards to resources, the earth is a closed system…the amounts of minerals that are on Earth do not increase or decrease, they just move around

Question 11, 12, 13 Question 11,12 A calorie is the amount of ENERGY required to change the TEMPERATURE of 1 gram of WATER by 1 degree CELSIUS. A CALORIMETER is used to collect and measure HEAT ENERGY. Question 13 Heat (calories) = Mass of Water (g) x Temperature Change of Water (oC) x 1 cal/g oC HEAT = 15g x 76˚ x 1 cal/g oC HEAT = 1,140 cal

Question 14, 15 Question 14 Energy Content (cal/g)= Heat Given off (cal)/Mass of fuel burned (g) 8,000 cal/2.1 g = cal/g Question 15 This is tricky… 1.8g of candle wax burns and raises the temperature of 100g of water by 18˚C; what is the heat (cal) per gram of candle wax? Heat=100g x 18 ˚=1800cal Heat/Gram of mass burned =1800cal/1.8g=100cal/g

Questions 16, 17 What does efficiency describe?
Efficiency describes how well a system changes energy from one form to another. We use systems (machines) to change energy from a form that is not useful to a form that is useful. Are any energy transitions 100% efficient? NO! In fact, as the complexity of a system increases, the efficiency of that system decreases.

Efficiency Problems Efficiency = (Energy Out/Energy In) x 100 Eff.=(986/3578) x 100 Eff.=27.6%

History of Fuel… In the early 1800’s = WOOD In the late 1800’s = COAL
In the early 1900’s = OIL Today = OIL Tomorrow = wind?, solar?, nuclear? hydro?

Energy Use/Value We use different resources based on…
Availability Price Fuel Content Technology We measure the value of fuel… Energy content Calorie/gram

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