Why does my Mac not work with the wifi if I stop using it for a while?

Whenever I stop using my Mac and it goes into sleep mode, I find that when I come back google chrome will not load, or anything else that uses my wifi. No matter how long I wait or refresh the page it always says it cannot load the page, my Mac is also not even 6 months old .I usually have to restart it then it will work again, does anyone know how I can fix it??