MAP Science Practice Test (Grades 3–5)

Explanation: 

Some mixtures can be separated back into their original parts, and some cannot. It depends on whether the materials actually change or just sit together. 

1) Marbles + Water: Yes [reversible]. 
Marbles don’t dissolve in water. They just sit at the bottom of the jar. You can simply pour off the water or pick out the marbles. 
The marbles and the water are both exactly the same as before you mixed them – this is a very easy-to-separate mixture. 

2) Salt + Water: Yes [reversible]. 
When you put salt in water, it dissolves. The salt seems to disappear, but it’s still there! If you heat the salt water and let the water evaporate, the salt crystals will be left behind. By covering the container (keeping the wather vapor gas trapped) you can get both materials back. 
This might take a little more work than separating marbles, but can be done. 

3) Yellow paint + Blue paint: No [irreversible]. 
When you mix yellow and blue paint together, you get green paint. The colors blend completely and you cannot separate the yellow from the blue again. No matter what you try, you can’t “un-mix” the green paint back into yellow and blue. This is an irreversible change. 

The correct answers: B, C.

Why B is correct: The stars aren’t actually moving in circles — it’s the Earth that’s spinning! Earth rotates (spins) on its axis once every 24 hours. Because we are standing on Earth and spinning with it, it looks to us like the stars are the ones moving across the sky, just like how trees seem to move past you when you spin around on a carousel.

Why C is correct: Look at the center of the circular pattern in the photo. There’s one point that doesn’t seem to move at all – everything else circles around it. That point is Polaris, the North Star. Polaris appears to stay still because it is located almost exactly above Earth’s North Pole – the point around which Earth spins. Since Earth’s axis points directly at Polaris, that star doesn’t seem to move while everything else circles around it, like the center of a carousel stays still while the edges spin.

➤ The circular trails in the photo are our evidence that Earth is rotating. If Earth stood still, the stars would appear as fixed dots, not arcs. The longer the exposure, the longer the arcs – which tells us Earth kept spinning the entire time the camera was open.

Why are the other answers wrong?

A: The stars are not physically flying in giant circles through space. They only appear to move that way because Earth is rotating. This is similar to sitting in a car and feeling like the trees are moving backward – but it’s actually you who is moving forward. Stars are actually extremely far away and barely move at all (relative to us).

D: Stars don't orbit the Moon. The Moon is much smaller than stars and orbits Earth, it has nothing to do with other stars apparent motion.