Unit 1 - Matter and Energy - Energy & Heat - Regents Flashcards
Energy
Ability to do work
Potential Energy
Stored Energy
Kinetic Energy
Energy of Motion
Five Forms of Energy
- Heat
- Light
- Electrical
- Nuclear
- Chemical
What occurs to energy in a physical and chemical change?
A change in energy occurs
What is the first law of thermodynamics?
Energy can never be created or destroyed, it can only transfer and change form.
What is Heat (5)
- Form of Energy
- NOT Temperature
- Heat flows from high heat to low heat
- Flow is never ever affected outside forces
- Measured in Joules (J)
(4 is the second law of thermodynamics)
1 Cal = ____ J
4.187 Joules
What is Temperature?
Measure of the average kinetic energy of a material.
What’s the celcius scale?
Based on water’s freezing point (0°C) and boiling point (100°C)
What’s the Kelvin Scale?
Zero Kelvin is absolute zero, where all energy is ceased.
Faranheit?
NEVER USED IN SCIENCE
Specific Heat Definition (1)
The amount of energy it takes to raise 1 gram of a substance by 1°C
Specific Heat: Crucial Info (5)
- Physical Property
- Units: J/g°C
- Specific Heat of Water: 4.18 J/g°C
- Different Materials respond differenly to heat
- Solid metals have a MUCH lower specific heat
Why is q = mc∆t used?
Determines amount of heat gained or lost when there is a temp. change
Vaporization
Liquid to Gas
Sublimation
Solid - Gas
Ex: Freeze Dried Food
Deposition
Gas to Solid
Ex: Frost in freezer and grass
Fusion
Liquid to Solid
What is true about the melting point and freezing point?
The temperature of MP and FP will always be equal.
Why is q = mHf used? (3)
- Used to calculate the heat transfer
- Only used when a phase change occurs
- Melting and Freezing
Why is q = mHv used? (3)
- Used to calculate heat transfer
- Only used when a phase change occurs
- Boiling and Condensing
Describe the motion of particles and phase changes of a graphical heating curve (4/6)
- Substance starts off as a solid
- Heat was added
- Increases the kinetic energy
- Increases speed of particles
- Substance goes through a phase change
- Heat was added
- Kinetic Energy stays the same
- Particle Speed stays the same
- Heat energy is focused on breaking the forces that hold molecules in place
- Potential Energy increases
Definition of Reactant
The starting material in a chemical reaction that is transformed.
Definition of Product
The transformed reactant as a result of a chemical change
Definition of Chemical Reaction
Chemical changes occur
When is there a chemical change in compounds? (2)
- Compounds are formed or decomposed
- Reactant disappear and products appear
What is the relationship between energy and chemical bonds? (3)
- Stored energy (potential) is found in bonds
- When bonds are broken & formed, amount of potential energy changes
- Reactants and Products don’t have same amount of energy
Definition of Enthalpy
Definition, how to calculate, what is used for measure
- Amount of heat absorbed/released
- DURING A CHEMICAL CHANGE
- Δ H can be calculated by:
Enthalpy of the Product - Enthalpy of Reactant - Measured in Joules (Heat energy)
Definition of Exothermic Reactions (4)
- A chemical/physical reaction
- Releases heat energy
- Products have less energy than reactants
- As a result, it produces heat to its surroundings
- Energy is seen on the product (right) side
Examples:
Δ H - Negative
Freezing and Condensation
Definition of Endothermic Reactions (5)
- A chemical/physical reaction
- Products have more potential energy than reactants
- Extra energy needs to be absorbed from surroundings
- As a result, heat is removed from surroundings
- Extra Energy is on the reactant (left) side
Examples:
Δ H - Positive
Melting and Boiling
Why are Exothermic and Endothermic Reactions chemical AND physical?
The absorption and release of energy can be physical or chemical, depending and how that occured
Exo. Chem. Reaction: Combustion of Gas
Exo. Phys. Reaction: Freezing
Endo. Chem. Reaction: Photosynthesis
Endo. Phys. Reaction: Boiling
Why does licking the back of a fridge feel like burning?
When your skin is in contact with very cold surfaces, there is a rapid loss of heat. Your nerves interpret this as a burning sensation.
(REMEMBER: IN CHEM, YOU DO NOT MATTER, THIS IS AN ENDOTHERMIC REACTION BECAUSE THE REFRIDGERATOR IS GAINING ENERGY FROM THEIR SURROUNDINGS. WE ARE THE SURROUNDINGS!!!!)
Definition of Boil
When the vapor pressure = atmospheric pressure
What is activation energy? (2)
- Amount of energy required to initiate a chemical reaction
- Amount of energy needed to reach the activation complex
What does activation energy ensure about molecular collisions?
Molecules collisions have enough energy to react and become products.
Definition of the Activation Complex
- Middle step during chemical reaction
- Highest PE
- Most Unstable
Definition of Forward Reaction
Process where reactants are turned into products
Definition of Reverse Reaction
Process where products are converted back into reactants.
How do you read a potential energy diagram?
(Reactant, Product, Activate Complex, Activation Energy, Enthalpy/Delta H)
Reactant - On far left
Product - On far right
Activated Complex: Peak found in middle
Activation Energy for Forward Reactions: Vertical distance of the peak & reactant
Activation Energy for Reverse Reactions:
Vertical distance from peak & product
Enthalpy: Difference between product and reactant
How do you know the strength of bonds based on potential energy? (3/3)
Lower Potential Energy:
- Strong bonds
- Atoms are Stable
- Takes a lot of energy to separate them.
Higher Potential Energy (Shallow Well):
- Weak bonds
- Atoms are Unstable
- Takes less energy to separate the
Definition of Catalyst (3)
- Speeds up chemical reaction without the catalyst going through a chemical change
- Activation energy AND ACTIVATION COMPLEX decreases
- Energy of Reactants and Products stay the same
