Chapter 10: Transfer of Heat and Its Effects Flashcards
(26 cards)
How does heat/thermal energy flow between regions of different temperatures.
Heat/Thermal energy flows from a region of higher temp to a region of lower temp.
What is the definition of temperature?
Temperature is the degree of hotness or coldness of an object.
What is the S.I. Unit of temperature, as well as the common unit of temperature?
The S.I. Unit is Kelvins (K) and the common unit is degree Celsius (°C)
How does the mass, volume, and density change when something absorbs heat?
Mass = Stays the same (mass can’t change)
Volume = Increases (Expansion)
Density = Decreases (Higher Volume and same Mass)
How does the mass, volume, and density change when something absorbs heat?
Mass = Stays the same (mass can’t change)
Volume = Decreases (Contraction)
Density = Increases (Lower Volume and same Mass)
What happens when things absorb heat?
They expand and increase in volume.
What happens when things lose heat?
They contract and decrease in volume.
What is density and what is it’s formula?
Density of a substance is its mass per unit volume.
Density= mass/volume
Which substances have a higher and lower density? A: Heated,
B: Cooled
The heated substance has a lower density due to the higher volume from expansion. The cooled substance has a higher density due to the lower volume from contraction.
What happens to molecules when heated? A: They get bigger. B: They move about faster.
The answer is B. Expansion occurs because the molecules move about faster, not because they grow bigger.
Why are overhead cables hung loosely when being installed in the summer?
application!!
During winter, the cables lose heat to the environment, become colder and contract. The cables were hung loosely in summer to prevent the cables from becoming tight and snapping due to contraction.
How is a hot rivet used to join two steel sheets together?
application!!
The rivet loses heat to the environment, cools down and contracts. This pulls the steel sheets together.
A bimetallic strip made with brass, which has an expansion coefficient of 18.9, and iron, which has an expansion coefficient of 1.2. How does the bimetallic strip act when heated?
application!!!
When heated, the brass expands faster than the iron as it has a larger expansion coefficient of 18,9 compared to iron’s 1.2. This makes the bimetallic strip bend downwards.
What is conduction?
Conduction is the process of heat transfer through a medium or material without any movement of the medium or material.
Why are metals good conductors of heat?
Metals are good conductors of heat as they have delocalized electrons.
What is convection?
Convection is the transfer of heat from one place to another by the movement of fluids like liquids and gases.
How does convection occur?
Warm fluids are less dense due to expansion, and rise. Cool fluids are denser due to contraction and sink. This sets up a convection current.
Why is a handle of a pan made of plastic, but the pan itself made of metal?
Plastic is an insulator of heat and heat is passed to your hand slowly, thus allowing your hand to not get scalded. Metal is a good conductor of heat and heat is passed to the food quickly, thus the food is cooked quickly.
Explain the process of conduction of a solid material from one end to the other in terms of particles.
Particles in the solid material gain heat and vibrate more vigourously. Particles collide with each other, and transfer energy from particle to particle.
How does a convection current get set up in a room with a heater at the bottom of the room?
The heater warms up the air at the bottom of the room, which expands, becomes less dense, and rises up to the top of the room. The air at the top of the room cools down, contracts, becomes denser, and sinks down to the bottom of the room. The cycle repeats and a convection current is formed.
How does a convection current get set up in a room with an air-conditioner at the top of the room?
The air-conditioner cools the air at the top of the room, which contracts, becomes denser and sinks to the bottom of the room. The air at the bottom of the room, warms up, expands, becomes less dense and rises up to the top of the room. The cycle repeats and sets up a convection current.
What is radiation?
Radiation is the transfer of heat, in the form of electromagnetic waves, from one place to another. It does not require a medium for transmission.
How does a vacuum (NOT THE CLEANING TOOL) affect conduction, convection and radiation from transferring heat?
The vacuum prevents conduction and convection from taking place, and it does not affect radiation at all as radiation can take place in a vacuum which conduction and convection cannot.
What are the 4 factors of an object that determine whether it is a good absorber and emitter of heat, and whether it is a good reflector of heat radiation?
- Colour
- Texture
- Surface area
- Temperature difference
