P2- Energy Transfer by heating

What is a conductor ?

a material that allows energy to move easily through it

What is an insulator ?

a material that doesn't allow energy to move easily through it

Describe what happens to the particles when energy is transferred by conduction in a metal.

The particles gain kinetic energy
From this kinetic energy, particles vibrate faster
The vibrating particles transfer energy to neighboring particles in the metal through collision until the whole metal is heated

Name 3 insulators ?

Glass, wood and plastic

Name 3 conductors?

Steel, Aluminium and Copper

Why does conduction occur in solids rather than in gases/liquids?

Conduction occurs in solids rather than in liquids/gases because the particles are more closely packed together than in comparison to liquids and gases that have particles that move freely.

Define thermal conductivity?

the measurement of how well a material conducts heat ( the ability to conduct heat )

The higher the thermal conductivity of a material, the higher _______

The higher the rate of energy transfer by conduction across material

Which material has a lower thermal conductivity : glass or metal

Glass, insulators have a low thermal conductivity

3 Factors that affect the rate of energy transfer by conduction?

thickness of material
the thermal conductivity
the temperature difference across the material

2 ways to reduce energy transfers? (unwanted heat loss) ?

using a thick material
using a material with a low thermal conductivity that can trap air ( insulator )

Define Specific heat capacity?

The specific heat capacity of a substance is the amount of energy it takes to increase the temperature of 1kg of the substance by 1degree C

Which material has a lower thermal conductivity ? Non metals or metals?

Non metals, low thermal conductivity = high specific heat capacity ( more energy required to increase temperature 1kg of substance by 1 degree)

What is the difference between thermal energy and temperature?

Thermal is the sum of the kinetic energy of particles in an object and is measured in Joules
Temperature is the measure of the average kinetic energy of particles and it is measured in Degrees

Why does an iceberg have higher thermal energy than a matchstick?

An iceberg has a larger sum of the kinetic energy of particles than a matchstick therefore icebergs have higher thermal energy than matchsticks.

How much thermal energy does a 2 kg steel block (c = 450 J/kg°C) lose when it cools from 300°C to 20°C?

252000 J

How hot does a 3.5 kg brick get if it’s heated from 20°C by 20,000 J (20 kJ)? SHC=840

26.8 C

If the temperature of a material increases, the increase in temperature depends (3):

mass of material
type of material
amount energy input into material

Why is it better to have a window made of two layers of glass with a layer of air trapped between them?

Both glass and air are insulators because they have low thermal conductivities.
The layer of air has the lowest thermal conductivity which reduces overall thermal conductivity. This makes it harder for energy to leave the window

Why is loft insulation so effective?

It traps air which helps to reduce heat lost from the home

The walls of houses are often built out of brick with an inner and an outer layer; there is a gap between the layers. Sometimes this gap is filled with a solid insulating material such as foam. Why is the foam effective in reducing heat loss?

The insulating material ( foam) as it has a lower thermal conductivity than the air it replaces

What happens to a material when it is heated up ( talk about particles and kinetic energy)?

When a material is heated up, the particles gain kinetic energy and start moving faster. This results in an increase in temperature and the material getting hotter

What colour surfaces are the best emitters of infrared radiation ?

Matt Black surfaces

What colour surfaces are the best reflectors of infrared radiation?

Shiny Silver surfaces

All objects emit radiation however, the hotter the object is the more___

infrared radiation it emits and the visible light

Both wavelength and intensity of radiation depend on____

the temperature of the object

Which wavelengths are the hottest?

Short wave lengths

What properties does a perfect black body have?

Perfect black bodies absorbs all infrared radiation
It also emits all the radiation
doesn't reflect or transmit radiation

What happens to the temperature of a body that absorbs and emits infrared radiation at the same rate?

It remains constant

What happens to the temperature of a body that absorbs infrared radiation faster than it emits?

It increases

What gases in the atmosphere change the balance of infrared radiation absorbed and emitted by the Earth?

greenhouses

Factors affecting the earths temperature?

concentration of greenhouse gases
infrared radiation absorbed by earths surface/atmosphere
infrared radiation emitted by earths surface/atmosphere

Explain. in terms of particles, how evaporation causes the cooling of water?

Particles gain kinetic energy and speed up
The fastest particles escape through then surface of the water
the remaining particles decrease in energy
This means the total thermal energy is decreased therefore the temperature decreases too

How do greenhouse gases keep the earth warm?

Infrared radiation from the sun warms the earth ground. The ground then emits long-wavelength infrared radiation. Greenhouse gases absorb it and then emit into the earths surface.

The specific heat capacity of aluminium block is 913 J per kg per °C and its temperature is increased by 10 °C. 4565 J of energy is transferred. Calculate the mass of the aluminium block.

500g

Why are data logs better than glass temperature

more precise/sensitive
reduces instruments random error