Science is pure, it is about knowledge - how and why things behave the way they do.
Engineering is applied, it uses scientific knowledge to engineer a solution to some problem.
For example, a scientist might measure the strength of bars made from various materials and of various sizes, determine a law expressing how much each material deforms under various loads and then attempt to explain the law in terms of more fundamental principles. An engineer designing a window lintel could use that information to determine of what material and how large the lintel should be.
In practice, this distiction is not always clear. Engineers often perform experiments to investigate phenomena; scientists often design solutions to practical problems. Still, the desire to make this distinction between purity and practicality endures. Such a boundary is clearly indistinct.
The engineer employs imagination to envision and ultimately to create what has never been. He asks "How?" of nature, and seeks to organize its knowledge toward service to man's imagination. The scientist employs curiosity to examine and ultimately to understand what has always been, but heretofore unexamined. He asks "Why?" of nature, and seeks to expand its knowledge, and with it man's imagination and capacity to transform his material world.
Engineering designs objects such as lintels to be parts of systems like buildings and communities. Engineering is the practice of complexity, of diverse units (spars, fairings, avionics, actuators, etc.) organized as a coherent system (airplane). Science is the practice of simplicity, looking at distinct units to comprehend their function according to describable and repeatable rules.