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