Can I use whatsapp with a number belonging to another phone I currently have a Samsung S5 phone but find it bulky to carry and as I use it mainly for old fashioned calls I was thinking of moving my simcard (and therefore phone number) to my old Motorola Razr. 
I understand that the S5 will effectively become like a small tablet and the email will still work on the S5 but will whatsapp if I am using the number on another phone?
Will my whatsapp contacts notice any difference or will it work exactly as it currently does?
Thanks
Answer is 'Yes', you can use it on your S5 seamlessly while using SIM in another device.

• Your Whatsapp contacts doesn't see any change.

• Remember Whatsapp can only be use on single device at a time(not whatsapp web) that means if you try to open it in your Moto device than you Galaxy device 's account will be closed.