3-5 Calculations (p 116 3.2)

Calculations (p 116) 3.2
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Slide 1: Diapositive
NatuurkundeMiddelbare schoolhavo, vwoLeerjaar 2

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Calculations (p 116) 3.2

Slide 1 - Diapositive

Slide 2 - Vidéo

Energy
  • During combustion energy is released in the form of heat and light.
  • Your body also releases energy during the combustion of food. This is used to move and to heat up the body. 

Slide 3 - Diapositive

Joule
Energy is measured in joule (J).
1 joule is a very small quantity so we rather work in kJ and MJ
1 kJ = 1 000 J
1MJ = 1 000 000 J

Slide 4 - Diapositive

Energy
  • Walking up one fight of stairs uses = 10 kJ
  • Running 1 km = 200kJ
  • 20% of energy used is by the brain
  • 14 year old person uses about
        11 000 kJ per day. 
  • Boys use a bit more.

Slide 5 - Diapositive

Food
  • On the label of food it is written how much energy is released during combustion.
  • 100 gram penutbutter = 2 690 kJ
  • Energy in food is also  
       indicated in the unit 
       kilocalories (kcal)
        1kcal = 4,2 kJ

Slide 6 - Diapositive

Heat of combustion
  • 1kg dry wood releses 16 MJ heat
  • 1kg coal releases 29 MJ heat/ energy
  • Heat of combustion - 
        The amount of energy that is released when buring 1kg
        of fuel.
  • Liquids are measured in liters and gasses in m3

Slide 7 - Diapositive

Natural gas
Hydrogen gas
Petrol
Diesel
Dry wood
Coal
Type of fuel                          Ammount.                           Energy                 HEAT of combus.

Slide 8 - Diapositive

Calculations using the table
How much energy is released when you burn 20 kg of dry wood?
(from the table you see the heat of combustion = 16 MJ)



Therefore it will be 16 x 20 = 320 MJ
Amount
1kg
20 kg
Heat
16 MJ
?

Slide 9 - Diapositive

Energy in food
  • This is mostly indicated per 100 gram (kJ/100g) and liquids in kJ/100ml
  • Nutritional value=  heat of combustion of food
  • Of all the food you eat the body uses:
           Carbohydrates, fats and protein
  • 1g protein/ carbohydrate = 17kJ
  • 1g fat = 38 kJ

Slide 10 - Diapositive

Nutritional value is the same as heat of combustion.
A
true
B
false

Slide 11 - Quiz

1kcal equals 4,2 kJ
A
true
B
false

Slide 12 - Quiz

The body uses carbohydrates, fats and hydrocarbons in foods.
A
true
B
false

Slide 13 - Quiz

The heat of combustion of a fat is higher that that of a hydrocarbon.
A
true
B
false

Slide 14 - Quiz

One liter of petrol has more energy than one liter of diesel.
A
true
B
false

Slide 15 - Quiz

Convert:
0,85 MJ =
A
0,000 85 kJ
B
0,85 kJ
C
850 kJ
D
850 000kJ

Slide 16 - Quiz

Convert:
250 000 J =
A
250 000 MJ
B
250 MJ
C
0,25 MJ

Slide 17 - Quiz

730 J =
A
730 000 kJ
B
730 kJ
C
0,73 kJ
D
0,000 73 kJ

Slide 18 - Quiz

Now do the following questions
29, 31, 32, 33 (blz 117)

Of question 31 insert a picture on the next slide.

Slide 19 - Diapositive

Insert a photo of your answer to question 31

Slide 20 - Question ouverte

How did the lesson go?

Slide 21 - Question ouverte