Is an object moving around earth (orbiting) at a constant speed accelerating

I swear my teacher loves to ask tricky questions!!! I'm in a basic astronomy class and we're learning about Newton's Laws (gravity etc). One of the questions my teacher has asked on homework is, "An object in orbit around the Earth, like the Space Station, moves with a constant speed called the circular velocity. Is an object moving around the Earth at a constant speed accelerating? Explain why or why not." I want to say that the object is not accelerating because it is at a constant speed... Acceleration refers to how rapidly the change in velocity happens and if the speed is constant, then there is no change in velocity occuring. Is that right??? Can anyone explain this to me?

You are wrong. Speed is not velocity. It is a "trick" question but it is one of the most important elements of mechanics/kinematics.

Although the SPEED is constant, the velocity is not.
Velocity is a vector and it has both speed and direction. It takes a force to change direction just as it does to change speed.

If you doubt that, take a car on an icy road and suddenly turn the steering wheel.
guess what? You don't turn. You go straight ( off the road half the time). You have not got sufficient friction to apply the necessary force and accelerate the car in its new direction.

So if the direction of the velocity is altering then there is a force and F=ma so there is also an acceleration.

Alternatively if you know that difference = final - initial
You can draw the velocity vector at some point in time then subtract the velocity vector that occurred a little while earlier. You will see that there IS a change in velocity and so that there must be an acceleration.

This was the starting point for Newton and his apple. Realizing an acceleration and a force was needed to keep the moon orbiting around the earth, or the earth around the sun he was pondering what could that force be.