Chapter 3 - Obtaining Energy from Fuels

Question 1

Carbohydrate

Answer 1

Nutrients made from carbon, hydrogen and oxygen that can be broken down into glucose for cellular respiration.

Question 2

Fats

Answer 2

Large non-polar molecules (triglycerides) that store energy in the body, which can then be oxidized to release energy.

Question 3

Protein

Answer 3

Molecules that have long chains of amino acids. Rarely used as an energy source for the body unless other stores are used up.

Question 4

Bomb Calorimeter

Answer 4

An apparatus which is used to measure the heat of combustion of fuels by burning a fuel in an insulated container and measuring the temperature change of the surrounding water.

Question 5

Calibration Factor

Answer 5

The amount of energy (in joules) required to raise a certain amount of water in a calorimeter by one degree celsius.

Question 6

Calorimetry

Answer 6

An experimental technique in which the amount of heat released or absorbed by a chemical reaction is calculated by measuring the temperature change of the surrounding water.

Question 7

Dietary Fibre

Answer 7

Also ‘cellulose’; an indigestible substance which makes up plant cell walls and provides no energy to the body.

Question 8

Energy Transformation

Answer 8

The process through which one type of energy (e.g. electrical) is converted to another (e.g. heat).

Question 9

Energy Efficiency

Answer 9

The percentage of energy from a source which is converted to useful energy.

Question 10

Limiting Reactant

Answer 10

The reactant that is completely used up in a reaction, which limits the amount of products that can be made.

Question 11

Solution Calorimetry

Answer 11

Calorimetry which measures the temperature change of the water for a reaction in solution (e.g. dissolving in water).

Question 12

Reagent

Answer 12

A substance added to a system to cause a chemical reaction (e.g. catalysts or enzymes).

Question 13

Thermal Energy Transferred Formula

Answer 13

q = mc∆T
q = energy (J)
m = mass (g)
c = specific heat capacity (4.18 J g⁻¹K⁻¹)
∆T = temperature change (°C or K)

Question 14

Energy of Electrical Calibration Formula

Answer 14

E = VIt
E = energy (J)
V = voltage (volts)
I = current (amps)
t = time (seconds)

Question 15

Energy of Chemical Calibration Formula***

Answer 15

E = n x ∆H (note: energy is in kJ)

Question 16

Calibration Factor Formula

Answer 16

CF = Energy Added / ∆T (note: CF is in J °C⁻¹)

Question 17

Energy of a Reaction Formula (using CF)***

Answer 17

E_{rxn = CF x ∆Trxn (note: E is in J)}

Question 18

Enthalpy of a Reaction Formula

Answer 18

∆H = E_{rxn / n (note: E is in kJ)}

Question 19

Percentage Energy Efficiency Formula***

Answer 19

% Energy Efficiency = Useful Energy / Energy Input x 100

Question 20

Greenhouse Gas

Answer 20

Gases found in the atmosphere that raise the surface temperature of the planet. For example, carbon dioxide and methane.

Question 21

Energy Content of Food Formula***

Answer 21

Energy Content = (energy transferred to water) / (change in mass of food during combustion) x 100

Question 22

Electrical Calibration

Answer 22

A method of calibrating a calorimeter by running a fixed current and voltage through a high resistance wire to heat water.

Question 23

Chemical Calibration

Answer 23

A method of calibrating a calorimeter by performing a reaction of known energy and measuring the temperature change of the surrounding water.