Physics 1a Flashcards
(28 cards)
How does an object heat up by infa red?
It will have to absorb more radiation than emmited
What properties absorb more radiation?
Dark Matt surfaces absorb infa red better than shiny and light surfaces
How are solids formed?
The solids: strong bonds of attraction, held into place, not much energy or vibration only around a fixed position
How are liquids formed?
Liquids: weakens bonds of attraction, close together but can move past each other, form irregular arrangements, more energy and vibration, and move randomly at low speeds
How are gases formed?
Gases: almost no forces of attraction, more energy vibration and kinetic energy. Free to move , travel in random directions at high speeds
How does conduction work?
CONDUCTION IS THE PROCESS WHERE VIBRATION PARTICLES PASS ON THEIR EXTRA KINETIC ENERGY TO ITHER PARTICLES by hitting into them
Is conduction better in more or less dense solids and why?
Usually faster in denser solids new she the particles are closer together so will collide more often
Why are metals good at conduction?
They are because because they have free electrons inside the metal
What is convection?
CONVECTION OCCURS WHEN THE MORE ENERGETIC PARTICLES MOVE FROM THE HOTTER REGION TO THE COOLER REGION AND TAKW THEIR HEAT WITH THEM.
How does an immersion heater work?
The water particles near the heater heats up and gets more energy so they start vibrating more. The water gets less dense and then rises. The hot water hits the cold water CONDUCTS HEAT. The cold water gets more dense and sinks. THe water goes round in circles until all hot
What is the subject of convection currents?
CHANGES IN DENSITY
How does a radiator heat up a room?
CONVECTION
How does has turn to liquid?
When a gas cools the particles slow down and lose kinetic energy the attraction force between the particles pull closer together. WATER VAPOUR WILL CONDENSE ID IT TOUCHES A COLS SURFACE
What affects the rate of evaporation?
If the temperature is higher(each particles energy is more)
If the density is lower(the forces between the particles is lower)
If the surface area is larger(the particles will be closer to the surface)
If the airflow over the liquid is greater
What affects the rate of condensation?
If the temperature of the gas is lower( the average energy will be lower)
If the temperature of the surface the gas touches is cold
If the density is higher(the forces will be stronger between them)
If the airflow is less
What is HEAT ENERGY TRANSFER? How is it affected?
Heat energy is radiates from any surface. It can be increase by having a bigger surface area. A smaller volume will cool quicker.
How are flasks made to reduce heat transfers?
There is a vacuum between the two walls to stop convection and conduction
The walls on either side of the vacuum are silver to minimise radiation
The bottle has insulating foam in the vacuum to stop conduction
The cork is made out of plastic, cork or foam to reduce heat conduction
How to humans reduce heat transfer?
The the cold the hairs stand on end the trap insulating air around the body to limit CONVECTION
When we are hot the blood vessels go to the surface of your skin to increase RADIATION
Animals living in hot places have big ears to increase RADIATION
How can you increase energy efficiency in your house?
Cavity wall insulation reduce RADIATION AND CONVECTION
Loft insulation to reduce CONDUCTION AND RADIATION
Draft proof to reduce CONVECTION
Hot water tank jacket reduces CONDUCTION AND RADIATION
Thick curtains to reduce CONDUCTION AND RADIATION
Double glazing
What is a U-value?
U-value shows how fast heat can transfer through a material. A material with a high u-value heat can transfer quickly
What is specific heat capacity?
Specific heat capacity tells you how much energy things can store. Materials which can gains lots of energy to warm up also release lots when cooling down
What is the specific heat capacity formula?
Energy transferred= mass X SPH X temperature change
E = m × c × θ
SHC is energy divided by mass times temperature change
E (divided by) m X θ
For example, how much energy must be transferred to raise the temperature of 2 kg of water from 20°C to 30°C?
(Water SHC is 4181)
E = m × c × θ (θ = 30 – 20 = 10°C) E = 2 × 4181 × 10 = 83,620 J or 83.62 kJ
What are the nine types of energy?
ELECTRICAL LIGHT SOUND KINETIC NUCLEAR HEAT GRAVITATIONAL POTENTIAL ELASTIC POTENTIAL CHEMICAL (food, fuels and batteries)
The last three are just how energy is stored
