Physics Ch. 15 Questions

6 September 2022
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question
What are the temperatures for freezing water on the Celsius and Fahrenheit scales? For boiling water?
answer
Water freezes at 0°C//32°F water boils at 100°C//212°F
question
What are the temperatures for freezing water and boiling water on the Kelvin temperature scale?
answer
water freezes at 273 K water boils at 373 K
question
What is meant by "translational" kinetic energy?
answer
Kinetic energy of motion that carries a molecule from one place to another (random molecular motion) defines Temperature temperature is proportional to translational kinetic energy
question
Which forms of energy determine temperature? Translational kinetic energy, rotational kinetic energy, vibrational kinetic energy, or all of these?
answer
Translational Kinetic Energy determines Temperature. Vibrational KE and Rotational KE (plus potential energy) contribute to overall energy of the substance.
question
What is meant when we say that a thermometer is in thermal equilibrium with another object?
answer
Heat no longer flows between the object and thermometer when both are at the same temperature. *When it is in thermal contact with something to be measured, energy will flow between both until their temps are equal; thermal equilibrium is established.
question
Is there a distinction between thermal energy and internal energy? Which term do physicists prefer?
answer
Thermal energy emphasizes heat flow (link between heat and temperature), whereas internal energy is the grand total of all energies inside a substance. Physicists prefer internal energy. *heat: energy in transit. Once transferred, it is no longer heat.
question
In which direction does heat flow spontaneously between hot and cold objects?
answer
From high temperature to low temperature. Ex.) touching ice; energy transfers from warm skin to cooler ice. *Heat: energy in transit. Once transferred, it is no longer heat.
question
Does a hot object contain internal energy or does it contain heat?
answer
A hot object contains nternal energy, not heat. Object contains translational KE of jostling molecules, rotational KE and other KE and PE from molecular forces.
question
How is heat similar to and different from internal energy?
answer
They are both forms of energy, but heat flows, whereas internal energy does not. Internal energy is only summation of all the substance's energies.
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What role does temperature have in the direction of heat flow?
answer
Heat flows spontaneously from high temperature to low temperature.
question
How is the energy value of foods determined?
answer
The food is burned and the energy released is measured.
question
Distinguish between a calorie and a Calorie.
answer
A Calorie is 1000 calories.
question
Distinguish between a calorie and a joule.
answer
1 calorie = 4.19 joules
question
How many joules (J) are needed to change the temperature of 1 gram of water by 1°C?
answer
4.19 J
question
Which warms up fastest when heat is applied: water, iron, or silver?
answer
Silver warms up faster than iron. Iron warms up faster than water. Ag: lowest specific heat capacity Fe: low spec heat capacity H2O: high spec heat capacity
question
Does a substance that heats up quickly have a high or a low specific heat capacity?
answer
A low specific heat capacity heats up quickly cools off quickly
question
Does a substance that cools off quickly have a high or a low specific heat capacity?
answer
A low specific heat capacity
question
How does the specific heat capacity of water compare with the specific heat capacities of other common materials?
answer
Water has a higher specific heat capacity than most common materials.
question
Northeastern Canada and much of Europe receive about the same amount of sunlight per unit area. Why, then, is Europe generally warmer in the winter?
answer
The gulf stream carries warm, high heat capacity water past the west coast of Europe.
question
According to the law of conservation of energy, if ocean water cools, then something else should warm. What is it that warms?
answer
The cooling ocean warms the air.
question
Why is the temperature fairly constant for landmasses surrounded by large bodies of water?
answer
Water has a high specific heat capacity.
question
Why do substances expand when their temperature is increased?
answer
Higher-temperature substances have greater molecular motion.
question
Why does a bimetallic strip bend with changes in temperature?
answer
The two metals expand at different rates.
question
Which generally expands more for an equal increase in temperature: solids or liquids?
answer
Liquids generally expand more than solids. *H2O ice is the weird one!
question
When the temperature of ice-cold water is increased slightly, does it undergo a net expansion or a net contraction?
answer
Contraction ice cracks, tries to shrink
question
Why is ice less dense than water?
answer
Ice crystallizes with an open structure, and the gaps that form between the water molecules in ice increase its volume.
question
Does "microscopic slush" in water tend to make it more dense or less dense?
answer
Less dense greater volume
question
What happens to the amount of "microscopic slush" in cold water when its temperature is increased?
answer
The amount of microscopic slush decreases as the temperature increases. melts, obviously!
question
At what temperature do the combined effects of contraction and expansion produce the smallest volume for water?
answer
4°C
question
Why does all the water in a lake have to be cooled to 4°C before the surface water can be cooled below 4°C?
answer
When water is cooled to 4°C, it sinks and deeper, warmer, water rises to the surface.