It is a big question because when we a in love with some opposite gender our heart and mind wishes to have a physical relation with that partner. When we are having physical relations that is called sex and a very emotional feeling flows through heart, mind and whole body during the period of physical relations. THAT FEELING MAY BE CALLED LOVE.
The other angle of love and sex depends on age of person’s involved in the relation. If they are new young teenagers they will have more attractions and wish towards physical relations (SEX) because of their hormonal changes in their body and it is a new world for them however if both partners are of middle age group they will wish for physical relations with emotional bond between them. If partners are in their 40’s they will have more emotional and social bondage between them and less physical relations and if partners are in 50’s then there are more then 90% social and emotional relations and only 10% chances of physical relations because in 50’s normally hormones and body of human beings are on declining sides and energy levels are low compared to their young age. Also in 50’s peoples have more maturity and surrounded with responsibilities. 
It can be said that age is a very big factor deciding about LOVE AND SEX. As per age of person involved it has different meaning of LOVE AND SEX for them. Also society gives recognition to love but not to sex(illegal or unsocial).