CHEM Knewton Alta 3.4 Energy

Heat capacity depends on __________.

the composition of the substance the amount of the substance

An object that is classified as having a low temperature will have __________ thermal energy.

low

The energy an object has by virtue of its position in a field is called:

potential energy Whether a gravitational field or an electromagnetic field, the energy an object has because of its position with respect to an attracting object is called potential energy.

Which is the largest unit of energy?

Calorie The Calorie, or food calorie, is 1,000 calories, each of which is larger than a joule. Remember that 1 calorie corresponds to 4.184J. Therefore, a calorie (cal) "contains" several joules. Joules is the smallest unit of energy in the list.

A chef places a cold glass of water into a hot pan. Which of the following is true about the heat flow between these two bodies?

Heat will flow from the pan to the water, making the water warmer and the pan colder until they are both the same temperature. Heat is the transfer of thermal energy between two bodies at different temperatures. Heat flows from substances with high temperatures to substances with low temperatures, thus making the warmer object cooler and the cooler object warmer. Remember that heat NEVER flows from the cooler object to the warmer object. The warmer object becomes cooler because it is losing heat energy to the cooler object.

What is the amount of energy required to raise one gram of water by 1∘ C?

a calorie

Which of the following is true regarding heat capacity?

all of the above Heat capacity is determined by the amount and type (composition) of substance that releases and absorbs heat. It can be calculated by using the equation C=q/ΔT.

Thermal energy flows spontaneously between objects from __________.

high temperature to low temperature

When a rubber band is stretched and waiting on your fingers, this is ______________ energy, and when you let the rubber band fly off of your fingers, this is ____________ energy.

potential, kinetic Potential energy is the energy an object has by virtue of its position in a field, while kinetic energy is the energy of motion.

A calorie is equal to the amount of energy required to __________.

raise the temperature of one gram of water by one degree Celsius

If an object absorbs heat, one would expect its temperature to __________.

increase When objects absorb heat, their temperatures rise (or increase). For instance, a frying pan absorbs heat from the stove so that it gets hot (its temperature increases).

What is the definition of energy?

the capacity to supply heat or do work

A small iron pan takes 382 J to heat up by 38 ∘C, while a large iron pan requires 2,933 J to heat up the same amount. Which pan will have the higher heat capacity?

the large iron pan Heat capacity depends on the amount, or mass, of the object. In this case, the large iron pan will have a higher heat capacity given that C(small pan)=382J/38 ∘C=10.05J/∘C C(large pan)=2,933J/38 ∘C=77.18J/∘C.

Which amount of water would have the greatest heat capacity?

the ocean Heat capacity depends on the amount or mass of the substance with which we are dealing. The ocean is an extremely large body of water (the largest amount of water from the given choices), so it would take an immense amount of heat energy to be dispersed throughout in order to raise the temperature of the entire body of water by one degree Celsius compared to the other choices.

Why are chemists interested in studying thermochemistry?

-Heat is often absorbed during reactions. -Heat is often released during chemical reactions. Heat is often absorbed and released during chemical reactions as a way of energy changing forms. Therefore, chemists study thermochemistry as a way to understand what is happening during certain chemical reactions.

The heat capacity of an object depends on its __________.

-composition -mass

Heat energy is measured in units of __________.

-joules -calories The units we use for measurements of heat energy are calories or joules. Degrees Celsius and degrees Kelvin are units of temperature, not heat energy.

David is cooking a brisket and needs his casserole dish to be exactly 150∘C. It takes 32,000 J to heat the casserole dish from 0∘C to 150∘C. What is the heat capacity of the dish in joules per degrees Celsius?

213 J/∘C

If a frying pan has a heat capacity of 500J/∘C and it absorbs 25,000 J of heat, what will be the change in temperature in degrees Celsius?

500 degrees Celsius C=qΔT ΔT×C=q ΔT=q/C ΔT=25,000 /J500 J/∘C ΔT=50∘C

An object absorbs 17,000 J of heat and, as a result, its temperature is raised from 45∘C to 75∘C. What is its heat capacity?

567J/∘C C=q/ΔT=(17,000 J)/(75∘C-45∘C)=567J/∘C.

Most thermometers use what property of metals to measure temperature?

ability to expand with rising temperature Mercury thermometers and bimetallic thermometers use the expansion of metals (or other substances) to measure temperature. This is done by firstly calibrating the device carefully and then measuring the level of the mercury or the degree of coiling in a metal strip.

Which object has the most gravitational potential energy?

an airplane in mid-flight An object's gravitational potential energy increases with increasing height and with increasing mass. Thus the plane, having both the highest altitude and greatest mass, will have the greatest potential energy.

The kind of energy stored within the bonds of molecules is called:

chemical potential energy The energy stored within covalent chemical bonds is called chemical potential energy, which is what is used to power our bodies in their day-to-day motion.

When an object's temperature __________, it will most likely contract.

decrease When an object's temperature decreases, it will most likely contract. Most (but not all) substances behave this way.

A cold pack utilizes what kind of reaction to cool your skin?

endothermic The chemical reaction in a cold pack absorbs heat from your skin, which is why it has this cooling property.

What is the SI unit of heat, work, and energy?

joules

In a car engine, chemical energy is transformed into:

mechanical energy Chemical energy is transformed into mechanical energy in a car engine. Mechanical energy is what makes the pistons in the engine move, which is what powers the car.

Which of the following is an example of an endothermic process?

melting ice cubes Melting ice cubes are an example of an endothermic process. The ice cubes absorb heat energy from the air around them and any other object (with more thermal energy than the ice cubes) with which they may be in contact. Burning sugar and a candle burning are both chemical reactions which give off heat energy, so they are both exothermic. When water vapor condenses, more energetic gas molecules become less energetic liquid molecules; the heat energy from the more energetic molecules in the gas phase is given off to the environment, making it an exothermic process.

An indirect measure of the thermal energy of an object is __________.

temperature

Which of the following objects has more kinetic energy than it does potential energy?

the pendulum of a grandfather clock at the lowest point of its arc of motion Kinetic energy is the energy of motion. Each of the objects above are motionless—with stored potential energy—except for the clock. At the bottom of its arc it will have the greatest kinetic energy, which is then converted to potential energy as it swings back up to one side.