Is there any easy way to tell the difference between impressionism, realism and abstrct

There are no hard and fast rules in my experience and what one person thinks is impressionist can be abstract for someone else. It is difficult to make general statements about categorising paintings, and there are many categories and sub categories available for the debate. However, taking a deep breath and the three categories in you question I would define Realism as a painting that tries to depict a scene exactly as it appeared in life including all the detail, Impressionism I think can be roughly defined as painting that depicts scenes from life but leaves out some detail and what the artist sees as extraneous matters resulting in a painting that tries to convey the 'atmosphere' of the scene (that could trigger another debate about defining atmosphere in a painting!), Abstract painting is generally painting that is not bound by the shape of scenes or objects or their hue and tone etc. but sets out the artist's thoughts about the subject matter in whatever manner he/she decides is appropriate. There is a whole body of art literature discussing the different styles of painting but I find the best style(s) is that that makes you feel 'wow' when you see it regardless of any category. Stands back and waits to be taken to task!

Not going to take you to task, Stub, I think you've described the differences very well. Impressionism does cover a very wide field - Cézanne, Monet, Renoir, Sickert?, Sisley, for instance. Do we include van Gogh? I suppose so, but of course the differences between these painters are vast. And some Impressionists became abstract artists - not actually that many, but arguably Piet Mondrian, Matisse, and others who wander into other genres as well. I've always thought of abstract painters as those who might base their work on things they've seen, but "abstract" it - so that their work isn't necessarily recognizable as whatever inspired it. And then you have Picasso, who moved between genres; and Dalí - who was in many technical ways quite a traditional painter: it was his subject matter that wasn't. I suppose I do wonder if it matters very much: it's all painting, of course. I think the big change, and the one that interests me most, isn't so much the external appearance, theme or subject matter, but the profound technical change that occurred when painters embraced the alla prima approach, from which few subsequently have departed, moving away from the slow build up of coloured glazes over monochrome studies. What's really interesting about that - well, I think - is the fact that acrylic really lends itself to that older method, because of course you don't have to wait an age for layers to dry, and (barring disasters) they won't crack either. This is also of interest when you move on to highly realistic painting - the best way to achieve that always was to work the painting up in layers over an accurate base study; and glazes score heavily here over the looser applications offered by alla prima painting in opaque colour.