Science year 2.2: energy effects

• Natuur, Leven en Technologie
• Middelbare school
• havo
• Leerjaar 2

2.2 Energy Effects

Learning goals

Learning goals

- Explain the three different types of heat transfer

- Identify which type of transfer is present in a situation

- Explain the difference between conductors and isolators and describe how they should be used

- Identify if a reaction is endothermic or exothermic

- explain the effect of catalysts on chemical reactions

Conduction

Conduction = heat transfer via direct contact.

Example = a pan transfers heat to food

Conduction

Heat transfer through direct contact between the particles in a substance

Insulators: not good at conducting heat 

plastic, cork, air, wood

Conductors: good at conducting heat

metals; copper, silver

Convection

Convection = heat transfer via air or water. 

Example = radiator warms the air in a room

Hot air has a lower density than cold air, therefore it will rise upwards

Cold air has a higher density than hot air, therefore it will sink

Radiation

Heat transfer in all directions through electromagnetic waves

Radiation does not need a medium to go from one place to another

Radiation can move through space 

Radiation

moves in all directions

does not need medium

when a chemical reaction needs heat, it's called endothermic

chemical reactions that release thermal energy(heat) to the environment are called exothermic

exotherm

endotherm

Catalysts

Each reaction needs energy to get started → activation energy

             Example: Heat is needed to start a fire (ignition temperature)

The activation energy can be lowered by catalysts (certain molecules) 

There are also catalysts in your body, they are called enzymes

convection is heat transfer through...

1. solid materials
2. fluids and gasses
3. nothing
4. glass

a catalyst makes is harder for a reaction to happen

1. true
2. false

Burning coal on a barbecue is an exothermic reaction

1. true
2. false

what is needed for conduction

1. molecules that can move around freely
2. no molecules at all
3. molecules very close to each other
4. al lot of different types of molecules

homework

Make: 12 until 21

Pages 18 until 22