Physics 1A (Energy) Flashcards
Describe the three ways that Heat Energy can be transferred?
1) Conduction. Heat energy is transferred when free electrons in a solid gains extra kinetic energy (KE) and collide with other free electrons to pass on heat energy.
2) Convection. When a fluid is heated each particle gains KE and move around faster. Their distance increases and it expands and becomes less dense. As it rises it displays the cooler dense fluid.
3) Radiation. Heat energy is transferred by infra-red (IR) radiation which involves objects emitting electromagnetic waves.
Explain why solar hot water panels have a Matt black surface?
A matt black surface adsorbs and emits infrared radiation more efficiently than lighter surfaces, ideal for heating water.
True or false?
1) Does an object that’s cooler than its surroundings emit more radiation than it adsorbs?
2) Does an object that’s hotter than its surroundings adsorb more radiation than it emits?
1) false
2) false
Describe the arrangement and movement of the particles in:
1) solids
2) liquids
3) gases
1) Particles are held close together by strong forces of attraction in a fixed regular position. They don’t poses much energy and only vibrate about their fixed positions.
2) Particles held close together but with weaker forces of attraction and can move past each other, forming irregular arrangements. They move in random directions at low speeds.
3) Almost no forces of attraction between particles. Particles have more energy than liquids or solids and are free to move in random directions at high speeds.
1) What is the name of the process where vibrating particles pass on their extra kinetic energy to neighbouring particles?
2) what type of heat transfer occurs in solids?
1) Kinetic Theory of Matter.
2) Conduction.
1) Describe how the heat from heater coils is transferred throughout the water in a kettle.
2) what is this process called?
1)
i) Heat energy from the coil is transferred to the water particles by conduction(particles collisions).
ii) Their energy increases so they start moving around faster making the distance between them increases.
ii) The water expands and is less dense causing the hot water to rise above the denser, cooler water.
iv) As hot water rises particles take heat energy with them and displaces the colder water making it sink towards the coil.
V) The cold water gets heated by the coil and the circulating cycle continues until boiling occurs.
2) Convection process (convection currents are all about CHANGES IN DENSITY).
How do the densities of liquids and gases change as you heat them?
To complete
1) What happens to the particles of a gas as it turns to a liquid?
2) What is the name given to the process where a gas turns to a liquid.
1)
i) As a gas cools the gas particles SLOW DOWN and LOOSE KINETIC ENERGY.
ii) The ATTRACTIVE FORCES between the particles pull them CLOSER together.
iii) When the TEMPERATURE gets cool enough and the gas particles get close enough together the gas changes state and becomes a liquid.
2) CONDENSATIONS.
Why does evaporation have a cooling effect on a liquid?
Liquid particles need enough KE for them to escape the liquid surface. The particles require LATENT heat which other particles close to the surface provided for them to escape. These loose heat and the liquid cools.
Describe two features of a vacuum flask that makes it good at keeping hot liquids hot?
i) Flask has double wall with a vacuum in between. This stops conduction and convection through the sides.
ii) The walls either side of vacuum are silvered. This reduces heat loss by radiation.
1) what can you tell from a material’s U value?
2) what property of a material tells you how much energy it can store?
3) Do heaters use materials that have a high or low heat capacity?
1) Shows how fast HEAT can TRANSFERS through a material.
2) Specific Heat Capacity. (Amount of energy needed to raise the temperature of a 1kg of a substance by 1 degC).
3) High (they need to store LARGE amounts of heat energy.
Name 9 types of energy and give an example of each.
1) ELECTRICAL - whenever a current flows.
2) LIGHT - from the Sun, light bulb etc.
3) SOUND - from loudspeakers or anything noisy.
4) KINETIC or MOVEMENTS - car, atoms, anything that’s moving.
5) NUCLEAR - released from nuclear reactions.
6) THERMAL or HEAT - flow from hot objects to cooler ones.
7) GRAVITATIONAL POTENTIALS - possessed by anything which can fall.
8) ELASTIC POTENTIAL - stretched springs, elastic, rubber bands etc.
9) CHEMICALS - possessed by food, fuels, batteries etc.
State the principle of the conservation of energy.
ENERGY can be TRANSFERRED usefully from one form to another, STORED or DISSIPATED - but it can never be CREATED or DESTROYED.
List the energy transformation that occurs in the following:
1) Electrical devices i.e television.
2) Batteries.
3) Electrical Generation (wind turbine).
4) Potential Energy (firing a bow and arrow).
5) Battery Powered toy car.
1) Electrical energy ➡️ Light, sound and heat energy.
2) Chemical energy ➡️ Electrical and heat energy.
3) Kinetic energy ➡️ Electrical and heat energy.
4) Elastic potential energy ➡️ Kinetic and heat energy.
5) Chemical energy ➡️ Electrical and sound / heat energy.
What is the useful type of energy delivered by a motor? In what form is energy wasted?
i) Kinetic energy.
ii) Heat energy.
