void setup() {
  Serial.begin(9600);
  pinMode(11, OUTPUT);
  digitalWrite(11, LOW);
}

void loop() {
  float beta = 3950;
  int analogValue = analogRead(A0);
  float celsius = 1 / (log(1 / (1023. / analogValue - 1)) / beta + 1.0 / 298.15) - 273.15;

  Serial.println(celsius);

  if (celsius > 25.0) {
    digitalWrite(11, HIGH);
  } else {
    digitalWrite(11, LOW);
  }

delay(1000);
}