The dawn of Common Core, and the emphasis on math and language arts, has made finding decent workbooks on elementary science difficult. I have spent countless hours pouring and testing what's out there and available to families. The news isn't great. Students overwhelmingly resist the workbooks currently on the market, insisting that they are boring, dry, and pointless.
I have found that students have generally liked and benefited from using just one series of science workbook, Read and Understand Science, published by Evan-Moor. Remember, It cannot be emphasized enough the importance of literature and other materials to supplement any science workbook you choose.
Evan-Moor Read and Understand Science (K - 6) - This series combines reading, workbook style activities, and hands-on science into one. It is easy to implement, but may require a bit more oversight than your typical workbooks because of the hands on component. Hands-on activities do not require the use of anything beyond a few simple household items.
Amazon tends to have the best price, but if you will be using one level with more than one child, the Evan-Moor website sells an ebook version which may be a better value in some circumstances.
In many cases, it can be best to forego workbooks for science and social studies altogether in favor of literature based alternatives.