Love scenes and sex scenes are not necessarily the same, although they can be. The most poignant love scene can play out without either partner touching. Conversely, a sex scene can take place without any love, such as lust between strangers or a rape.
Either way, the writer's responsibility is to describe what is happening from point of view (POV) of the characters and to connect the reader to what's at stake in the story's plot and theme. In other words, both love and sex scenes are tied in to the plot of the story and a character's story arc; otherwise they are superfluous and may appear hollow, shallow or pointless.
The key to writing an effective scene from a passionate lusty romp to a bittersweet lover's fairwell that involves no sex, lies in the language of emotion. In his 1995 book, "Stein on Writing" by St. Martin's Griffin (New York), Sol Stein wrote that "the main flaw in most love scenes is [that[ the reader's emotions have been insufficiently considered by the writer. The primary erogenous zone is in the head, and that's where the reader experiences writing." ultimately both sex scene and love scene must engage a reader's emotions.
Use Conflict
"The most essential ingredients in love scenes," says Stein, "are tension and tenderness." Like any good scene, the main ingredients are: arouse interest; delay; then finally reward. Conflict of any kind provides the essential delay aspect that grips the reader in the story. Hence, the love triangle, or misunderstanding, betrayal, or lack of trust, etc. Conflict heightens emotions and creates tension that moves the pages. When conflict and sexual tension are tied in with overall plot and theme, then the story will engage the reader more deeply.
Use Sensual Language
Sensual writing lies at the heart of a love scene as well as a sex scene; without the emotional tie-in provided by sensual language the narrative is simply describing the act. Some of the best love scenes were written by classic writers like Thomas Hardy and D.H. Laurence, who used vivid imagery, metaphor and powerful evocative verbs to arouse the emotions of the reader – without ever describing the sexual act.
Using the POV of the omniscient voice in his 1891 novel "Tess of the d'Urbervilles", Thomas Hardy evokes powerful images of sexuality in a simple bucolic scene of Southwest England:
"Amid the oozing fatness and warm ferments of Frome Vale, at the season when the rush of juices could almost be heard below the hiss of fertilization, it was impossible that the most fanciful love should not grow passionate. The ready hearts existing there were impregnated by their surroundings."
Every verb, noun and modifier provides a compelling image of sensuality, passion and urgency. Words such as "oozing fatness" "warm ferments" "rush of juices" "impregnated" evoke deep emotions within the reader. What's interesting is that Hardy evokes such strong sexual emotions without even mentioning sex (though he does mention love).
Use Metaphor & Imagery
D.H. Lawrence provides some of the most evokative love scenes in his 1928 novel, "Lady Chatterley's Lover" with powerful metaphor and imagery: "And softly, with that marvelous swoon-like caress of his hand in pure soft desire, softly he stroked the silky slop of her loins, down, down ... and she felt herself melting in the flame." Lawrence's metaphoric imagery remains as powerful today as it was when written several decades ago.
Both Hardy and Lawrence apply metaphor, vivid images, strong verbs and suggestive setting to create rich and compelling scenes that readers will enjoy at many levels.