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Molecular kinetic theory and internal energy
This is a mind map about molecular kinetic theory and internal energy. The main contents include: specific heat capacity, internal energy and heat, and molecular kinetic theory.
編輯於2024-02-05 11:46:40
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Molecular kinetic theory and internal energy
molecular kinetic theory
Objects are made up of a large number of molecules
Molecular characteristics: small, invisible to the naked eye.
Molecules are the smallest substances that maintain the chemical properties of matter.
Note: Viruses and microorganisms are not molecules
Molecules are constantly moving in an irregular manner
diffusion
definition
The phenomenon of different substances entering each other as they pick up each other due to molecular motion
Diffusion speed
Gases diffuse the fastest, followed by liquids and solids.
Nature
The essence of diffusion is microscopic but the phenomenon of diffusion is macroscopic
The phenomenon of diffusion explains
1. Molecules are constantly moving irregularly
2. There are gaps between molecules
There are interactions between molecules
molecular interactions
Gravity Example: Tension spring - produces gravitational force
Repulsive force Example: Compression spring - generates repulsive force
The simultaneous attraction and repulsion between molecules are collectively called forces
molecular kinetic theory
Objects are composed of a large number of molecules. The molecules are constantly moving irregularly. There are attraction and repulsion forces between the molecules.
Key point: Memorize every word without landing it.
At a certain range, gravity and repulsion exist simultaneously, but they can be ignored when the distance is too large.
Internal energy and heat
Temperature and thermal motion
Temperature reflects the intensity of molecular motion, so people call the irregular motion within an object thermal motion.
internal energy of object
definition
The sum of the kinetic energy of all molecules of an object and the potential energy of intermolecular interactions
! ! ! Special note: The molecules of all objects are constantly moving irregularly, so all objects have internal energy [Note: it is all objects] and the internal energy cannot be 0
How to change internal energy
heat transfer
The direct transfer of internal energy from one object to another
The premise is that there must be a temperature difference
acting
Convert other forms of energy into internal energy or internal energy into other forms of energy
The essence is the mutual conversion of mechanical energy and internal energy
focus
1. For the same substance, the internal energy will definitely increase as the temperature increases, but the temperature does not necessarily increase as the internal energy increases. Example: Ice melts into water.
2. When work is done on an object, the internal energy increases and the temperature rises. The temperature of an object that performs work on the outside decreases
Burn: release heat
calorific value
Definition: We call the ratio of the heat Q released by complete combustion of the fuel to the fuel mass m, called the calorific value of this fuel. The symbol is represented by q.
q=Q/m
The unit of q is: J/kg
The unit of Q is: J
The unit of m is: kg
The calorific value of fuel is only related to the type of fuel (the calorific value of different fuels is generally different)
Specific heat capacity
An object’s ability to absorb heat
Experimental exploration: Comparing the heat absorption capabilities of different substances
Method: Control variable method
The mass is equal, the temperature is the same, the heating time is the same
Conclusion: The amount of heat an object absorbs is not only related to its mass and temperature changes, but also related to the substance it is.
Specific heat capacity
Definition: Specific heat capacity represents the ability of an object to absorb heat
Calculation formula: c=Q/mΔt
The unit of c is: J/(kg.℃)
The unit of Q is: J
The unit of m is: kg
The unit of Δt is: ℃
Notice
1. Specific heat capacity is a characteristic of a substance and is only related to the type and state of the substance.
2. Different substances generally have different specific heat capacities.
3. The specific heat capacity of liquids is generally greater than that of solids