Ch 10: Temperature & Heat
Whenever a gas is compressed
work must be done on the gas
When you apply an alcohol swab to your skin, it feels cool because
your skin transfers a bit of heat to the liquid alcohol and the alcohol evaporates
The amount of heat needed to raise the temperature of 1 gram of water by 1°C is
41.9 joules
When 10 grams of hot water cool by 1°C, the amount of heat given off is
41.9 joules
Room temperature on the Kelvin scale is about
300 K.
A box of graham crackers is labeled "120 Calories per serving." Assuming this means 120 kcal, and recalling that 4.16 J = 1 cal, the energy of a serving of the graham crackers is about
5 × 10^5 J
While studying for this quiz you realize that you still have 100 g of lukewarm coffee at 40°C left in a paper cup. When you pour 20 g of boiling water into the cup, the temperature of the resulting coffee-like mixture will be now
50°C.
A mixture consists of 70 g of ice and 60 g of liquid water, both at 0°C. (The latent heat of fusion of water is 80 cal/g and the specific heat capacity of water is 1.0 cal/g C°.) The amount of heat that must be added to melt all of the ice is about
70 x 80 = 5600 cal
The temperature of 100 g of water is to be raised from 10°C to 90°C. The energy needed to do this is about
8 × 10^3 cal
Which unit represents the most energy?
Calorie
Which temperature scales have equal sized degrees?
Celsius and Kelvin
Which temperature scale has the smallest sized degrees?
Fahrenheit
Which of the following units is not an energy unit?
Horsepower
Water freezes at 273° on the ________ scale
Kelvin
A temperature difference of 10 Celsius degrees is also equal to a temperature difference of 10 on the
Kelvin scale.
Which object is hotter?
Object 1 at T = 0° C
Objects A and B are at the same temperature. Object A now has its temperature increased by one Fahrenheit degree, while B has its temperature increased by one Kelvin degree. Which object now has higher temperature?
Object B
The temperature of a 50 g sample of aluminum is raised from 20 C to 60 C when 440 cal of heat are added. The specific heat capacity of the aluminum is
Q = (m)(s)(t) 440 = (50)(s)(60-20) S = 440/(50)(40) S = 0.22 cal/g C°
which process does not transfer heat energy between objects?
Reflection
Four samples of steel, lead, alcohol, and glass all have the same mass and are all initially at 20°C. After 100 calories of heat are added to each sample, the final temperatures are 38.2°C for the steel, 85.6°C for the lead, 23.4°C for the alcohol, and 30°C for the glass. Which of these four materials has the largest specific heat capacity?
The alcohol
Two identical objects, one light colored and the other dark colored, are at the same elevated temperature, 50°C. You now place them in a dark, much cooler room. Which object will reach the room's temperature first?
The dark colored object
Two identical objects, one light colored and the other dark colored, are at the same cool temperature. Then, you place them outside, on a warm day, in direct sunlight. Which object will warm up faster?
The dark one
compare the internal energy of one gram of steam to that of one gram of water if both are at 100°C
The internal energy of the steam will be higher
On a cold winter's morning you awake and step out of bed. One foot is on the tile floor and the other is on a rug on the floor. Which statement is true?
The tile feels colder because it conducts heat more rapidly away from your foot
The lowest possible temperature a body can approach is called
absolute zero
Pour a liter of water at 40°C into a liter of water at 20°C and the final temperature of the two becomes
at or about 30°C.
Absolute zero is the temperature
at which an ideal gas would exert zero pressure
In which is the temperature greater?
boiling-hot tea in a fire-engine pail, boiling-hot tea in a cup (both the same)
Hot cider is poured into a metal cup. Shortly thereafter the handle of the cup becomes hot. This is due to the process of
conduction.
As a piece of metal with a hole in it cools, the diameter of the hole
decreases.
The term heat in physics is
energy transferred to a body because of a difference in temperature
Heat is a form of energy, and it has long been known that heat energy will naturally flow
from hot to cold objects.
When you touch a hot potato with your finger, energy flows
from the potato to your finger.
When you touch a cold piece of ice with your finger, energy flows
from your finger to the ice.
After working hard outside on a hot summer day, placing a towel soaked in cold water on your head can feel very good. The reason the towel feels cold to you is that
heat conducts from your head to the towel, lowering your temperature
The moderate temperatures of islands throughout the world has much to do with water's
high specific heat capacity.
The amount of heat is often measured in calories. If I add 1 calorie of heat energy to 1 gram of water, the temperature of the water will
increase by 1°C
When the temperature of the air in a balloon is raised, the volume of the balloon
increases
Heat energy is measured in units of
joules, calories (both of these)
When an iron ring is heated, the hole becomes
larger.
One of water's interesting thermal properties is that when heated it takes a relatively
long time in changing temperature
The fact that desert sand is very hot in the day and very cold at night is evidence that the specific heat capacity of sand is relatively
low
The quantity of heat that a substance can transfer relates to its
mass, specific heat capacity, change in temperature (all of the above)
Pour two liters of water at 40°C into one liter of water at 20°C and the final temperature of the two becomes
more than 30°C
Heat energy travels from an object with a high
temperature to an object with a lower temperature
