Chemistry Test 5-1-2015
1 Cal equals how many calories?
1 Cal= 1000 calories
How many joules in 1 Cal?
1 Cal= 4184 joules
Carbohydrates/Proteins are how many kJ's and how many Cal's?
17 kJ/g and 4 Cal/g
How many calories are in 1 pound(454 grams) of proteins/Carbohydrates?
1816 calories
Fats are how many kJ's and how many Cal's?
38 kJ/g and 9 Cal/g
1 calorie equals how many joules?
4.184 joules
Specific heat of water?
4.184 joules/grams * Celsius
How many calories are in 1 pound (454 grams) of fat?
4086 calories
Delta H
A change in enthalpy signals a change in energy for the system (energy has been absorbed or released)
Which has more energy: a pound of fat or a pound of carbs(Proteins)?
A pound of fat
If Delta H is positive then the reaction is...
Absorbed(Endothermic)
When ammonium chloride dissolves in a beaker of water, the beaker becomes cold to touch. Why?
All of the heat energy was absorbed and used up in the reaction (endothermic)
Heat capacity
Amount of heat needed to raise the temperature of an object by 1 degree Celsius
Temperature
Average motion of molecules
Why is the joule the SI unit for energy and heat?
Because heat is the flow of energy
C means
Cal
A " " is a well insulated container used to measure temperature changes
Calorimeter
The study of heat flow and heat measurement is called
Calorimetry
The study of heat flow and heat measurement is called....
Calorimetry
On the average, " " suppy 17j/g*c (4 Cal/g) of energy
Carbohydrates
The symbol Delta H litterally means a " " in enthalpy
Change
Endothermic reactions
Consume heat in order for the reaction to go forward
Different types of food contain...
Different amounts of energy(Different types of bonds)
How can enthalpy be calculated for an equation where the coefficients have be doubled?
Double the enthalpy as well
If the coeficcients of a balanced equation are doubled, the enthalpy change for the reaction is
Doubled
A reaction that has a positive enthalpy can be described as...
Endothermic
The delta H for an " " reaction will always be a positive sign
Endothermic
The enthalpy of a substance is similar too, but not exactly the same as, the....
Energy
The heat absorbed or released in a reaction depends on a quantity called...
Energy
Energy is equal too....
Enthalpy and Heat
What does Hess's law say about the enthalpy changes for a net reaction?
Enthalpy for a net reaction can be determined by summing up all of the enthalpys for the individual steps
Combustion
Example of an exothermic reaction
Combustion reactions (burning hydrocarbons) would be classified as
Exothermic
T or F "Bond breaking" in a chemical reaction releases energy
False Bond forming
T or F Heat is transferred between two objects that are "the same temperature"
False Different
T or F An "exothermic" reaction absorbs heat from the environment
False Endothermic
T or F If a reaction is endothermic, the amount if heat appears on the "right" side of the arrow in the balanced equation
False Left
Tf means
Final temperature
Explain how a calorimeter is used to determine the quantity of heat transferred in a chemical reaction.
First, a Calorimeter takes the heat of water that is in it. After placing a metal in the water, the Calorimeter takes the difference between the last and first temperatures (Tf-Ti) to find the amount of heat transferred
Provide an analogy that explains why bond breaking requires energy
Force's of energy are required to break things (Ex. Putting hands together/pulling them apart)
The words calorimeter ,calorimetry, and calorie are all derived from the Latin word calor, which means....
Heat
The amount of heat needed to raise an objects temperature depends on its ....
Heat capacity
The amount of heat needed to raise the temp. Of a container of water (of any size) from 14 degrees to 15 degrees is
Heat capacity
Specific heat
Heat capacity of 1 gram of a substance
______ law describes how to find the net enthalpy changes for a series of reactions
Hess's law
Heat always travels from...
High to low concentration
Provide two examples from daily life that demonstrates how heat us transferred from one object to another
Holding hands Camp fires Cooking food Opening a refrigerator Straightening hair
Hess's Law
If series of reactions are added together, the enthalpy change for the net equation will be the sum of the enthalpy changes for the individual steps
Ti means
Initial temperature
Enthalpy
Is the sum of potential(stored) and kinetic(used) energy of a system
Explain why Hess's law is useful in the chemistry lab
It allows for enthalpy to be calculated for reactions that can not be performed directly
BONUS Who's the coolest person you know?
Johniah :3
In an exothermic reactions, products will always be " " than reactants.
Less
If Delta H is negative then heat is...
Let go(Exothermic)
Good conductors have..
Lower heat capacity The ability to transfer energy quickly Allows them to transer(or gain) heat easily
m means
Mass
General equation for finding heat?
Mass * delta tempuratue* specific heat
You must know the number of " " of reactants involved in a reaction to calculate delta H
Moles
What is meant by the standard state of an element?
Most stable form of an element under standard conditions (1 atm and 25 degrees celsius)
The prefix exo- in the word exothermic means?
Outside
Foods are reacted with " " in a labratory calorimeter to determine there energy values
Oxygen
Conditions such as temperature, " ", and the physical states of the substances in a reaction can affect delta H
Pressure
Exothermic reactions
Produce heat,will be in product. Heat,like energy, is measured in joules
Compare the enthalpy of the reactants and the products in both exothermic and endothermic reactions.
Products are lower than that of reactants for exothermic reactions
Qsur means
Q of surrounding
Qrxn means
Q reaction
Finding Delta H for a reaction?
Qrxn= -qsur Or Qsur=-qrxn The heat transfered in a reaction, qrxn, is equal in magnitude but opposite in sign to the heat absorbed by the surrounding
What happens to enthalpy if a reaction is reversed?
Signs are changed Ex: positive to negative Or Negative to positive
Why does your body store unused proteins(cabrs) as fats?
Since proteins(carbs) has 4 Cal per gram and fat has more (9 Cal per gram) the unused proteins are more efficiently stored as fat
Every substance has a " " which tells you how much heat is necessary to raise the temperature of 1 gram of the substance by 1 Celsius degree....
Specific heat
The enthalpy change measured at 1 atm and 25 degrees Celsius,when the reactants and products are in their standard states, is called a " "
Standard enthalpy change
Insulators
Take large amounts of energy to heat or cool (Water,antifreeze)
A transfer of heat is detected by measuring a " " change
Tempuratue
Joule
The SI unit for energy
Food labels are measured in..
The amount of energy to consume this amount of food
Heat of vaporization
The amount of heat required to move from liquid to gas states
Heat of Fusion
The amount of heat required to move from solid to liquid states
Heat
The energy that is transferred from one object to another
How is enthalpy of a substance related to the energy of a substance?
The enthalpy os a substance is simillar but not exactly the same as the energy of a substance
Thermochemistry
The study of changes im heat in chemical reactions
Calorimetry
The study of heat flow and heat measurement *Calorimetry experiments can determine heat of reactions, or enthalpy changes, by making accurate measurements of temperature changes in a calorimeter*
If the total number of calories is not "burned" then...
They are stored by the body
Heat
Transfer of energy
T or F All combustion reations are "exothermic"
True
T or F Energy can be stored in the "chemical bonds" of a substance
True
T or F It is "energy" that maintains your body temperature close to 37 degrees
True
" " has one of the highest specific heats of any common substance
Water
Can a reaction proceed in more then one direction?
Yes because energy can go in reverse
If you were given delta H of a reaction could you determine wheter the reaction was exothermic or endothermic?
Yes, if delta H is positive then the reaction is endothermic. If delta H is negative them the reaction is exothermic