my laptop is heating for normal usage like browsing should i reinstall zorin os
This greatly depends on the hardware configuration. On older laptops, you may experience heat up on simple tasks. Most of what is available today in software and web content is based on newer hardware. Simple ads, animations, photo rendering, carousels and even client/server communication can be enough to tax 7+ year old hardware.
On top of that, if you have a gpu card in use constantly, instead of on demand, this will increase your pc's temperature as well. You shouldn't need your gpu to render web content. This is one of the first things I'd check and change in order to reduce your pc's temperatures.
You may also want to check that all fans are working.
If you are overclocking you should expect this. It's also one of the reasons that overclocking reduces the life of cpu's and gpu's.
Without access to your machine or more information this is about as close to a solution as will ever be available.
bro before i had no issue but after reinstalling iam having this issue my ram usage 1.5 gb without any apps open
Gnome, by itself will use about a gig of ram. Xfce won't be much better at 700mb. This goes up depending on number of virtual workspaces, monitors and what was accessed recently.
Increase your swap file size and decrease the access time if you have less than 12gb of ram. Keep the number of tabs open in Chrome to a minimum. Don't open to many other applications. Trade using your favorite applications to less memory intensive applications. Increase the amount of ram in your computer.
Those are the main ways to increase ram efficiency.
Most software today is going to use more ram because of the "better graphics" provided. This isn't just in software developers because the developers of the graphics libraries are basing their minimal requirements in machines that aren't that old.
System specs please
Laptops have poor ventilation and are prone to dust accumulation. Try cleaning the inside.
Along with the suggestions above (Clean the vents), ensure that you have TLP and thermald installed:
sudo apt install --reinstall thermald tlp