Flour: Liquid or Solid?

A solid is like the rock we used: definite shape, volume and mass. It was hard in the hand. A liquid is like water: no definite shape, definite volume and mass. Flour behaves much like water in some ways but not in others.

Question: Is flour a liquid or a solid?


Flour (Any flour will work as long as it is finely ground.)

2 Clean measuring cups

Materials for the Project

This Project uses flour, 2 measuring cups, a scale, a magnifying glass and a plate or tray.

2 Glasses



Tray or plate

Magnifying glass


Pour the water from one glass into the other

Examine the water.

Mass the two measuring cups separately

Measuring cup on scale

The small measuring cup has a mass of 269.4g.

The base mass of the large measuring cup is 490.0g.

The base mass of the large measuring cup is 490.0g.

Measure out 125 ml (1/2 cup) flour in one measuring cup





Examine the flour

Mass the flour and measuring cup

Measuring cup with flour

A half cup of flour raises the mass to 3326.8g.

Tap the measuring cup on your hand a dozen or more times, then check the volume again

Mass the flour and cup again

Pour the flour into the other measuring cup

Mass the flour in this measuring cup

Put a pinch of flour on the tray

Examine this flour with the magnifying glass

Measuring cup holding half a cup of flour

Dumped into the measuring cup the flour is almost half a cup.

Clean up your equipment and lab area

(If the measuring cups were very clean, the flour can be returned to the kitchen.)


Describe how the water pours:

Describe the water (taste, color, smell):

Measuring cup with a third of a cup of packed flour in it.

Tapping the cup on a hand reduces the flour to a third of a cup.

Describe the flour (taste, color, smell)

Mass of flour in first cup:

Mass of flour in second cup:

Describe how the flour pours from one cup into the other cup:

Volume of flour in cup:

Volume of flour in cup after tapping:

Describe the flour seen with the magnifying glass:

Measuring cup of flour on scale

After tapping the cup of flour, the mass is 326.7g.


Find any difference in the mass of flour in the first and second measuring cups.

Find any difference in volume of the flour before and after tapping on the measuring cup.


Compare how flour pours into the measuring cup with a liquid such as water or oil does.

Compare how flour feels to how water feels.

Flour in the large measuring cup has a mass of 547.1g.

Flour in the large measuring cup has a mass of 547.1g.

Why does the flour change when it is tapped on your hand?

Why does the flour’s mass change after it is tapped?

Why does the tapped flour pour differently from the untapped flour?

Why does the flour have a different mass n the second measuring cup?

Does the flour have a definite volume? Why do you think so?

Does the flour have a definite mass? Why do you think so?

Does the flour have a definite shape? Why do you think so?

Is flour a liquid or a solid? Use your observations to support your opinion.


Measuring cup with flour residue

A layer of flour remains in the measuring cup.

What I Found Out:

Water pours easily and smoothly from one glass to another. Water has no color or smell. It feels wet and smooth on the fingers and the tongue.

I used plain white flour so it was white. It had a clean dusty smell. It was gritty on my tongue and tasted like paste.

When I tapped the measuring cup of flour on my hand, the surface leveled out. Then it started to shrink. The volume shrank by a quarter from 1/2c to 1/3c.

When I poured the flour into the measuring cup, it slid off the scoop easily. After being tapped, the flour was stuck in the measuring cup. I had to tap on the bottom to get the flour to go into the second cup. It fill down in chunks. Some remained on the sides of the first measuring cup.

The mass went down 0.1g (from 57.4g to 57.3g) after I tapped on the flour. It went down another 0.2g (from 57.3g to 57.1g) in the second measuring cup.

When I scattered a pinch of flour on the plate, it landed in little piles. Under the magnifying glass the flour looked like tiny grains of sand.

Flour on plate with magnifying glass

Scattered flour on a plate for examination with a magnifying glass.

Flour feels gritty instead of smooth like the water. Both poured easily but the flour slid more than poured.

I think the flour had lots of air mixed in with it in the measuring cup. When I tapped the cup on my hand, the bits of flour fell together and pushed the air out. The loss of mass was the mass of the air forced out by the tapping.

After the flour is tapped, the grains are tight against each other. The air mixed in let the grains of flour slide. Without the air, the grains could not slide so the flour fell in chunks.

Some of the flour does not fall out of the measuring cup so the mass is less. Both the water and the oil did the same thing.

I think flour does have a definite volume but only if it is tapped a lot to force the air out. Flour out of the bag does not have a definite volume as it can contain different amounts of air.

Flour does have a definite mass. This can change a little due to air mixed in with the flour.

Flour out of the bag does not have a definite shape. It changes to fit the container it is in. Flour does have a definite shape if you look at the individual grains.

I think flour is a solid. It does have a definite volume, mass and shape. It acts like a liquid because the grains are so small especially when they are mixed with air.