Do particles act like waves on large scales? I've seen illustrations of particles being particles and then becoming waves momentarily on impact before going back to being particles. But I picture it as particles behaving like waves on the grand scale. Are the particles and waves measured on the same scale? Basically what I'm trying to say is, is saying lightwave particle duality anything like saying $H_{2}O$ molecule water wave duality? Or is that just the classical interpretation?
 A: Particles do not become waves, nor waves waves become particles, nor any other thing in the between.
The terminology of being a particle or a wave is, in the classical literature, addressed to the solutions of the Newton's equations and the D'Alambert equation, respectively, but nevertheless has no direct experimental meaning, even in the classical picture (without going to quantum mechanics). In fact, keep in mind that the equations are only a way to predict and describe quantities that can be measured in a laboratory, and the latter ones are the characteristics that really matter. For example, although counterintuitive, you may think that a ball is a particle because you somehow see it, but what actually happens is that your eyes absorb the photons scattered by the ball: in this respect a ball in no more of a particle than anything else you can scatter photons on. Likewise when you measure energy, momentum and so forth. 
Equations in quantum mechanics and quantum field theory tend to be D'Alambert like, therefore people tended to use the unfortunate terminology of particles behaving like waves (or anything else of that sort). However, the mathematical description is nothing but a framework and a language that allows you to predict the quantities that you will eventually measure in a laboratory. In particular, the observables that one deals with are most of the times scattering amplitudes and transmissions coefficients. Such quantities naturally arise out of an elegant description that makes use of fields as operators on some Fock spaces acting on elements of a system; in order to obtain finite quantities many mathematical constructions are necessary and sometimes people tend to address physical meaning to each of those steps, although they have none, being only a language that allows us to describe and precisely predict new outcomes.
In this respect, many equivalent formulations of the same theory may arise, some making use of this and some of that other description and formalism; as such, every interpretation of the mathematics is equally correct (or incorrect). When in a laboratory, you only measure the outcomes, that is, a number (energy, momentum, scattering amplitudes), however this number has been generated. The bottom line is that the terminology used in these contexts is sometimes misleading because it tries to make sense of a mathematical formulation, whilst from the point of view of the physics the only true quantities are the ones you can directly measure, no matter the name you want to give the underlying formalism.
A: 
I've seen illustrations of particles being particles and then becoming waves momentarily on impact before going back to being particles.

This is  a misleading description of what happens at the microscopic level, the underlying level of nature, where quantum mechanics reigns.
When talking of particles with dimensions smaller than nanometers ($10^{-9}~\text{m}$) one does not really have particles, but quantum mechanical entities. The dual nature misrepresented in the sentence above is described by the mathematics of quantum mechanics. On impact and towards impacting, a wave function describes the behaviour, a solution of the quantum mechanical boundary problem for the scattering. This wavefunction squared gives the probability of the scattering happening. It is this probability that has a wave nature, i.e. many instances have to be gathered of the impact and then the wave nature can be seen in the "probability of impact" distribution.
Take an electron and send it to pass through two slits:

One at a time a random hit is seen in the top frames. After an accumulation an interference pattern appears. This is the wave nature of the electron, the dots are the particle nature since they can be imagined as coming from a small billiard ball. But particles at that size are quantum mechanical entities, not classical particles.

But I picture it as particles behaving like waves on the grand scale.

No. The quantum mechanical scale is controlled by the size of $\hbar$ , a tiny number . It is only in very special set-ups that the quantum mechanical nature may appear in synergy. For example lasers, or superconductivity. 

Are the particles and waves measured on the same scale?

No. The electron in the example above is supposed to be a point particle and experimentally  a very tiny limit exists. The wave like undulations of the  probability distribution appear at a few microns or so.

Basically what I'm trying to say is, is saying lightwave particle duality anything like saying H2O molecule water wave duality? Or is that just the classical interpretation?

The $H_2 O$ is an underlying framework for the appearance of the energy wave on water. As explained above the wave nature of elementary particles is not a matter wave or an energy wave , but a wave in the probability of interaction pattern.
