concatenating string in the property being observed in the observer

components.ui-slider.js

import Ember from 'ember';

export default Ember.Component.extend({
  propChanged: function(){
    console.log('prop changed');
  }.observes('prop')
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle'
});

routes.application.js

import Ember from 'ember';

export default Ember.Route.extend({
  m:{age:25,salary:1000},
  model(){
    return this.get('m');
  },
  actions:{
    changeAge(){
      console.log("change age");
      this.set('m.age',100);
    }
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
{{model.age}} 
<button {{action 'changeAge'}}>Change Age</button>
<br>
{{ui-slider prop=model.age}}
{{outlet}}
<br>
<br>

templates.components.ui-slider.hbs

{{yield}}

twiddle.json

{
  "version": "0.9.2",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.6.0",
    "ember-data": "2.6.0",
    "ember-template-compiler": "2.6.0"
  }
}