4 - Energy and Matter Flashcards
What is energy?
Energy is the ability to effect a change in matter. It can also be defined as the ability or capacity to perform work.
EX: Heat
What is Matter?
Matter is the building blocks of the universe. Everything we can touch is made up of matter. Matter exists in three states: solid, liquid, and gas.
EX: Deez nuts
What is Potential Energy?
Potential energy is stored energy.
Examples of potential energy are water behind a dam, electrical energy in a batter, and a suspended weight that can fall or drop.
What is Kinetic Energy?
Kinetic energy is energy doing work.
Examples are water flowing over a dam, a battery lighting a bulb, and a falling weight.
What is stated under the Law of Conservation of Energy?
Energy cannot be created or destroyed; it is simply changed from one form to another.
EX: Liquid water absorbing heat to vaporize into a gas, then rejecting heat energy to the surrounding air to condense back into a liquid.
What is weight?
Weight is the gravitational force exerted by the earth on an object. USA uses the US Customary units of weight: Ounce, Pound, and Ton.
What is mass?
Mass is the quantity of material within a material regardless of weight.
EX: The amount of iron in one 1”^3 of iron
What is the conversion rate of one pound to one kilogram?
2.2 lb = 1 Kg
What is density?
Density is a substance’s mass per unit of volume. This refers to the amount of a substance within a given amount of space.
What is Avogadro’s Law?
This states that at equal pressures and temperatures, a specific number of molecules of one gas will take up the same space as the same number of gas molecules of a different gas, regardless of mass.
What is Specific volume?
In order to compensate for the volume differences between different gasses due to different masses, we use a measurement called specific volume. This is the volume of a specific amount of gas under standard conditions, which is 68F/20C and 14.7 psia/101.3kPa)
Ex: (Specific volumes of 1kg)
- Dry, clean air = 0.849 m^3
- Hydrogen = 11.17 m^3
If a gas has a greater specific volume than air, the gas is called a light gas. If it occupies more, it is classified as a heavy gas.
Specific volume can be conceptualized as a the inverse of density. The higher a specific volume, the lower its density.
What is Specific gravity?
Specific gravity is the ratio of the mass of a certain volume of a liquid or a solid compared to the mass of an equal volume of water, which has a specific gravity of one. Objects with a lesser SG than one will float on water, objects with a greater value will sink.
What is Relative Density?
Relative density is defined as the ratio of the mass of a certain volume of a gas as compared to the mass of an equal volume of hydrogen.
What is Force?
Force is energy applied to matter that, unless counteracted by opposing forces, causes a change in the matter’s velocity.
FORMULA: Force = Mass X Acceleration due to gravity
What is Work?
Work is force multiplied by the distance through which it travels. The US Customary unit of work is called the foot-pound. This is the amount of work done in lifting a 1-lb weight a vertical distance of 1 ft.
FORMULA: Work = Force X Distance
EX: Calculation for lifting a weight of 2,000 lb a vertical distance of 10’
20,000 ftlb = 2,000lb X 10’
What is Power?
Power is the rate at which work is performed. The US Customary unit of mechanical power is horsepower.
CONVERSION: 1 hp = 550 ft-lb/s
FORMULA: Power = Work/Time
EX: A 2000 lb weight is lifted 10’ in two minutes
166.7 ft-lb/s = 20,000 ft-lb / 120 s
What is heat?
Heat is a form of energy that results in the motion of atoms. As the motion of atoms increased, so does heat. Heat always travels from a substance at a higher temperature to a substance at a lower temperature. Adding heat in a substance may greatly affect the nature of the substance. For example, heat causes most substances to expand; .
What is cold?
Cold means low temperature or lack of heat. Cold is the result of removing heat. A refrigerator produces cold b drawing away heat from the inside of the refrigerator cabinet.
What is temperature?
Temperature is a measure of the heat intensity or heat level of a substance.
What are the freezing and boiling temperatures of water for Fahrenheit and Celsius?
Fahrenheit: (Freezing: 32F, Boiling: 212F) Celsius: (Freezing: 0C, Boiling: 100C)
What is the conversion formula for Celsius to Fahrenheit and vise versa?
F = 9/5 X C + 32
C = (F - 32) X 5/9
What is Ambient Temperature?
Ambient temperature is the temperature of the air surrounding an object.
What is specific heat capacity?
The specific heat capacity of a substance is the amount of heat added or released to change the temperature of one pound of a substance by 1F.
What is a BTU?
BTU stands for British Thermal Unit. It is the US Customary unit of heat, and defines the amount of heat required to raise the temperature of 1 lb of water by 1F.
What is Enthalpy?
What is specific Enthalpy?
Enthalpy, as it is used in refrigeration work, is the total amount of heat in a substance, calculated from an accepted reference temperature.
Acceptable reference temp (32F /0C for water, -40F/-40C for refrigerant)
Specific Enthalpy is enthalpy per unit of mass. It is measured in BTUs per lb.
FORMULA: h = H/m
What is Radiation?
Radiation is the transfer of heat by heat rays.
Ex: Rays of light, heat from the sun
What is Conduction?
Conduction is the flow of heat through a material due to molecular vibrations in the material
EX: One end of an iron rod gradually transferring heat to the other end.
What is Convection?
Convection is the movement of heat from one place to another by way of a liquid or gas
Ex: A forced air furnace moves heated air from the furnace to the interior of a home
What is a solid?
A solid is any physical substance that keeps its shape even when not contained.
What is a liquid?
A liquid is any substance that has no definite shape but has a definite volume. A liquid takes the shape of its container.
What is a gas?
A gas is any physical substance with no definite shape or volume, which expands to fill its container.
What is latent heat?
Heat that brings about a change of state with no change in temperature is called latent heat. When a substance is condensing from a vapor to a liquid for example, any heat introduced that induces this change is called latent heat, because it does not change the actual temperature, only the state.
What is sensible heat?
Heat that causes a change in the temperature of a substance is called sensible heat. When heat is added to a substance and the temperature rises as the heat is added, the increase in heat is sensible heat.
How is sensible heat related to superheat / subcool?
Superheat and subcool are simply sensible heat when applied to the working concepts of a refrigeration circuit. When liquid refrigerant vaporizes in the evaporator and becomes fully vapor, any additional heat introduced raises the temperature of the refrigerant and is known as superheat. Vise versa, when compressed vapor condenses in the condenser and becomes a liquid, any additional heat taken out of the refrigerant is known as subcool.
What is a ton considered in refrigeration?
A ton of refrigeration represents the amount of heat energy absorbed when one ton (2000 lb) of ice melts during one 24-hour day.
How is refrigeration tonnage converted to BTUs?
1 ton = 12,000 BTU/hr
