Modeling Matter Chapter 2 Test Review

Why did the sugar and citric acid dissolve when mixed with the water?

• The sugar and citric acid molecules were not attracted to the water molecules.

• The sugar and citric acid molecules were attracted to the water molecules.

Why did the pepper and cumin not dissolve when mixed with the water?

• The pepper and cumin molecules were attracted to the water molecules.

• The pepper and cumin molecules were not attracted to the water molecules.

Which would allow attraction between molecules?

• Molecules separating

• Molecules mixing

• Molecules forming a sediment

• Molecules forming a layer

Answer explanation

Remember, in our experiment, the sugar and citric acid evenly mixed because their molecules were attracted to the water molecules.

Tags

NGSS.MS-PS2-5

Choose all that apply for molecules of a solid:

• molecules are far apart

• slowest moving molecules/don't vibrate much

• molecules are very close together

• molecules move fast

Answer explanation

This is an example of molecules of a solid. The molecules are tightly compacted which means they won't move or vibrate very much and if they do move, it would be very slowly.

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

Choose all that apply for molecules of a liquid:

• molecules "slide" around one another

• slowest moving molecules/don't vibrate much

• molecules are very close together

• molecules are fastest moving of the three states of matter

Answer explanation

This is an example of molecules of a liquid. The molecules are not as tightly compacted as a solid which means they would "slide" around one another. They would move faster than a solid's molecules, however that wasn't an answer choice :)

Tags

NGSS.MS-PS1-4

Choose all that apply for molecules of a gas:

• molecules "slide" around one another

• slowest moving molecules/don't vibrate much

• molecules are very far apart compared to the other states of matter

• molecules are fastest moving of the three states of matter

Answer explanation

This is an example of molecules of a gas. The molecules are very far apart from one another. This extra room allows for the molecules to move faster than molecules of a solid or a liquid.

Tags

NGSS.MS-PS1-4

In Solving Dissolving, we read about Maya who was wondering why the sugar disappeared when it was mixed with water. They decided to sit the cup of sugar water in the window. After a dew days, what did Maya observe and why?

• Maya observed nothing left in the cup. All the water and sugar evaporated.

• Maya observed water still in the cup but no sugar. The sugar evaporated.

• Maya observed small grains of sugar left in the cup. The water evaporated.

• Maya observed sugar and water still in the cup. Nothing evaporated.

Answer explanation

Evaporation is one way to separate a mixture.

Tags

NGSS.5-PS1-2

NGSS.5-PS1-4

Select all that apply. Which are too small to be seen with your own eyes?

• Particles

• Substances

• Atoms

• Molecules

• Mixtures

Answer explanation

Particles and atoms are the same thing. They are too small to be seen with our own eyes because they are at the nanoscale level. Molecules are combinations of 2 or more atoms or particles, but are still too small to be seen with our own eyes. We can see substances like water and salt with our own eyes because there are millions of molecules that compose that substance. Mixtures are combinations of substances so we can see those with our own eyes as well.

Select all that apply. How can you remove DISSOLVED solids from mixtures such as sugar water or sea water?

• Filter

• Evaporation

• Creating another mixture and combining it

• Boiling

Answer explanation

They weren't asking you to separate the salt from the water in the sea water. They were asking how to separate a solid substance that had dissolved. Think back to the book Solving Dissolving. They put the sugar water in a cup and put it in the window for it to evaporate. That left behind sugar. Something else they could have done was boil the sugar water and that would have left behind the sugar as well just as evaporation did.

True or False: In evaporation, the water and the dissolved solid both evaporate and disappear.

• True

• False

Answer explanation

In Solving Dissolving, when Maya placed the sugar water cup in the window sill, after a few days, only the water had evaporated. It left behind the sugar that had dissolved in the water.

Tags

NGSS.MS-PS3-4