Thermal energy Concepts

Question 1

What is thermal energy?

Answer 1

Thermal energy is the energy stored in hot objects due the movement (vibration) of the particles.

Question 2

What is heat?

Answer 2

Heat is an energy transfer method of thermal energy.

Hot to cold objects (TRAVELS)

Question 3

What is temperature?

Answer 3

Temperature is the average kinetic energy of the object.

Question 4

What is specific heat capacity?

Answer 4

Specific heat capacity is the amount of energy required to raised 1kg of a substance by 1 degree celcius.

E= mcT

Question 5

What is specific Latent heat?

Answer 5

The amount of energy required the change phases of a substance, while the temperature stays the same. (HEATING)

The amount of energy released to change the phase of a substance and the temperature stays the same. (COOLING)

Question 6

How is heat energy transferred?

Answer 6

When something is heated (heat source), the particles it contains all are given energy.

1. They gain kinetic energy and move around faster. (this is what the thermometer measures).
2. They gain potential energy when the particles move father apart.

Question 7

What does the thermometer measure?

Answer 7

The temperature, average kinetic energy of the substance.

Question 8

Why does objects expand when they get hotter?

Answer 8

This is because when solids, liquid or gas is heated the particles gain kinetic energy and vibrate faster which takes up more space. Thermal expansions and thermal contraction is due to the kinetic energy of the particles.

Question 9

If objects are the same temperature why do they feel different?

Answer 9

This is because of the conductivity level of the material. Thermal conductors conducts heat much faster that is why you feel these objects hotter or colder than insulators like paper.

Question 10

What is thermal equilibrium?

Answer 10

Objects are at thermal equilibrium when they are at the same temperature. No energy is transferred between their thermal store.

Question 11

What are the properties of a solid?

Answer 11

The particles are in fixed arrangement (lattice)

• Small vibration but the particles are fixed due to strong forces of attraction
• Fixed shape and volume

Question 12

What are the properties of a liquid?

Answer 12

• Particles can flow through each other.
• No fixed shape but fixed volume.
• Lattice

Question 13

What are the properties of a gas?

Answer 13

• Particles have high kinetic energy and move around
• No fixed shape or volume
• Can be compressed

Question 14

What is thermal conduction?

Answer 14

Thermal conduction is the movement of heat (thermal energy) through a material.

Question 15

What is thermal conductivity?

Answer 15

Thermal conductivity is a measure of how well a material allows heat (thermal energy) to pass through.

Question 16

What are conductors?

Answer 16

Conductors are materials that allow heat to pass through (high thermal conductivity).

Question 17

What are insualtors?

Answer 17

Insulators are materials that does not allow heat (thermal energy) to pass through. They have low thermal conductivity.

Question 18

Why are insulators good to prevent heat loss?

Answer 18

Since insulators are materials that does not allow heat the pass through, it prevents heat from escaping like jackets.

THIS IS BECAUSE heat always travel from hot temperature to cold temperature.

Question 19

Why is the thickness of an insulator important?

Answer 19

Thickness of an insulator is important as the thicker the insulator material the better it will stop the thermal energy from conducting.

Question 20

What is conduction?

Answer 20

Conduction is a the process of heat transfer in solid through vibration of particles passing along the kinetic energy to the neighboring particles.

Question 21

Why are metals good conductor of heat?

Answer 21

Metals are a good conductor of heat due to delocalised electrons.

Question 22

What is convection?

Answer 22

Convection is the process of heat transfer in fluids through convection current (hotter fluid are less dense and rises)

Question 23

What is radition?

Answer 23

Radiation is the process of heat transfer through electromagnetic waves.

It is the process of heat transfer through infrared waves.

Question 24

What colour material are good emitters and absorbers of infrared radiation?

Answer 24

Dark, matt surfaces are good absorbers and emitters of infrared radiation.

Light, shiny surfaces like silver are poor absorbers and emitters of infrared radiation. (REFLECTS THE RADIATION).

Question 25

What is the strong forces of attraction between the particles called?

Answer 25

Inter-molecular forces

Question 26

What is lantent fusion?

Answer 26

Latent fusion is the lantent heat require to change states between solid and liquid.

Question 27

What is latent vaporisation?

Answer 27

Latent vaporisation is the latent heat required to change states between liquids and gases?

Question 28

Why is latent vaporisation greater than latent fusion?

Answer 28

Latent vaporisation is greater that latent fusion. This is because latent heat is the amount of energy absorbed or released by the substance during a state change, while the temperature remains the same. Therefore, to change states from solid to liquid only a few amount of energy is required to loosen the intermolecular forces to allow the particles to flow through. And vice versa, to change from liquid to solid only few amount of energy needs to be released to tighten the intermolecular forces. However, to change from liquid to gas or gas to liquid a large amount of energy needs to be realeased or absorbed as the intermolecular foreces needs to be completely broken for gas.

Question 29

What is thermal energy formula

Answer 29

E= m * specific heat capacity * change in temperature

Question 30

What is change in energy formula?

Answer 30

Delta E= Power * time

Question 31

What is latent heat formula?

Answer 31

E (thermal)= mL

Question 32

What is the difference between positive heating and negative heating?

Answer 32

Positive heating is when energy is being added to the object and it will become hotter.

Negative heating is when energy is being removed from the object and it becomes colder.

Question 33

Hand indicator concept?

Answer 33

When we touch an object we feel it hot or cold depending on how energy is transferred.

• If energy is transferred into our hands, the objects feel hot.
• If energy is transferred from our hand to the object, then our hands feel cold.

Question 34

What are the properties of an incandscent light?

Answer 34

1. High melting point
2. Small specific heat capacity
3. High resistence

Question 35

How does an incadscent light works?

Answer 35

When an incandscent light bulb is connected to a power source the elctrical current flows through the filament. Resistence in the filament cause it to heat up (collisions). As the filament heats up and reaches high temperatures; it begins to glow and emit light.

Question 36

What is thermal expansion?

Answer 36

Thermal expansion is when materials are heated the particles it contains gains more kinetic energy which means the object will expand in all directions, potentially increasing it’s volume. This is because due to higher kinetic energy the particles vibrate/move harder and faster causing it to separate more from each other, which takes up a larger space.

The average distance between them increase.

Question 37

What is it meant by when objects have reached thermal equilibrium?

Answer 37

The heat only flows if two objects have a difference in temperature (average kinetic energy of the particles in the substance). Heat flows from hot to colder objects. After the heat flow, when both objects are at the same temperature, it means they have reached thermal equilibirum. So, no more heat transfer will take place.

Question 38

What is the difference between boiling and evaporation.

Answer 38

Both boiling and evaporation are types of vaporization, when a substance change state between liquid and gas.

In boiling, it changes between liquid to gas at the boiling point. Boiling happens throughout the substance (observed as bubbles).

Evaporation is a change of state between liquid and gas that can happen at any temperature between the melting and boiling point. It takes place only at the surface of the liquid.

Question 39

When to material are at the same temperature describe the energy?

Answer 39

When two materials are at the same temperature both material average kinetic energy of the particles are the same because temperature is a measure of the average kinetic energy of the particles of the substance.

However, the state determines the state energy (potential energy) of the matter. This is because the state energy of the liquid or gas is higher than solid because the particles are future apart which means they store greater potential energy.

Question 40

What is the energy changes that happens in heating or changing states?

Answer 40

During heating/cooling of substance (which is represented as the diagonal lines in heating or cooling curves) the temperature changes which meant the average kinetic energy of the particles changes so the kinetic energy of the matter changes which state energy remains the same.

However, during a phase change (plateau in cooling and heating curves) the temperature remains constant as the energy is used to strengthen/loosen the inter molecular forces and change the distance between the particles. Thus, the state energy (potential energy) changes while the kinetic energy remains constant.

Question 41

What is the difference between sea breeze and land breeze?

Answer 41

Sea breeze is the wind blown from the sea to the land during the day. This is because during the day the land heats up more (through the heat energy provided by the sun) than the sea because water has higher specific heat capacity. Thus, the warmer air particles over the land rises and the cooler air particles over the sea blows to the land, creating a convection current.

During the night land breeze happen. This is because the land cools down faster as the sea (water) has abosorb more energy so it cools slower. This means that the colder air particles over the land blows to the sea. While, the warmer air particles over the sea have more kinetic energy and is less dense so it rises. Creating a convection current.

THIS IS ALSO LINKED WITH THE PRESSURE.

Question 41

Why does steam cause more burns that boiling water at the same temperature?

Answer 41

Water vapour holds more energy at 100 degree celcius that equivalent of the water particles. This is because water vapour absorbs more energy in the form of latent heat of vaporisation, while boiling water particles have only energy absorb to heat- up the water. Thus, when we touch steam it releases larger amount of heat than liquid.

Question 42

How does evaporation cools down a liquid?

Answer 42

Evaporation allow energy to leave the system, so the temperature of the water will not be as high. Evaporation occurs when more energetic particles moving near the surface of the liquid have enough kinetic energy to break the bonds and become gas and escape to the surrounding. Additionally, the water molecules that evaporate have required energy to change state from liquid to gas. Thus, when the particles with the most energy leaves, they takes the energy with them out of the system. The average kinetic energy of the liquid is reduced (reduce in temperature). Therefore, liquids is cooled by evaporation.