Gas

from tkinter import *
import random
import math
import pickle

SIDE=500
DIAM=5
dt=.001

R=8.314
n=5
T=100
m=1


class Particles:
    def __init__(self,x,y,part_num):
        self.shape=[x,y,x+DIAM,y+DIAM]
        self.vel=[(math.sqrt(2*(2*T*part_num/n)/m))/math.sqrt(2),(math.sqrt(2*(2*T*part_num/n)/m))/math.sqrt(2)]
    def move(self):
        self.shape=[self.shape[0]+self.vel[0]*dt,self.shape[1]+self.vel[1]*dt,self.shape[0]+self.vel[0]*dt+DIAM,self.shape[1]+self.vel[1]*dt+DIAM]
    def vert_wall(self):
        self.vel[0]=-self.vel[0]
    def hor_wall(self):
        self.vel[1]=-self.vel[1]
    def collide(self,other_particle,angle,dist):
        a=self.vel
        b=other_particle.vel
        a=[a[0]*math.cos(-angle)-a[1]*math.sin(-angle),a[0]*math.sin(-angle)+a[1]*math.cos(-angle)]
        b=[b[0]*math.cos(-angle)-b[1]*math.sin(-angle),b[0]*math.sin(-angle)+b[1]*math.cos(-angle)]
        (a[0],b[0])=(b[0],a[0])
        a=[a[0]*math.cos(angle)-a[1]*math.sin(angle),a[0]*math.sin(angle)+a[1]*math.cos(angle)]
        b=[b[0]*math.cos(angle)-b[1]*math.sin(angle),b[0]*math.sin(angle)+b[1]*math.cos(angle)]
        self.vel=a
        other_particle.vel=b
        
        

parts=[]
i=0
space=int(SIDE/(2*DIAM))
for x in range(1,space):
    for y in range(1,space):
        if i<n:
            parts.append(Particles(x*2*DIAM,y*2*DIAM,i))
        i+=1

for t in range(100):
    for part in parts:
        part.move()
        if part.shape[0]<0 or part.shape[2]>SIDE:
            part.vert_wall()
        if part.shape[1]<0 or part.shape[3]>SIDE:
            part.hor_wall()
    for a in range(len(parts)):
        for b in range(a+1,len(parts)):
            ax=parts[a].shape[0]
            ay=parts[a].shape[1]
            bx=parts[b].shape[0]
            by=parts[b].shape[1]
            dist=math.hypot(bx-ax,by-ay)
            if dist<DIAM:
                try:
                    angle=math.atan((by-ay)/(bx-ax))
                except:
                    angle=math.pi/2
                parts[a].collide(parts[b],angle,dist)