In a five-fold serial dilution of a 20 ug/ml solution, all tube dilutions are 1/5. what is the substance concentration in the third tube of this series?

In the third tube, the concentration is 0.16 ug/mL

Explanation:

In the first step, the solution is diluted by 5. Then, the concentration will be

20 ug/mL / 5 = 4 ug/mL

Then, in the second step this 4 ug / ml solution is diluted by a factor of five again:

4 ug /ml / 5 = 0.8 ug/mL

This solution is then diluted again by 5 and the concentration in the third tube will be then:

0.8 ug/mL / 5 = 0.16 ug/mL

Another way to calculate this is to divide the original concentration by the dilution factor ( 5 in this case) elevated to the number of dilutions. In this case:

Concentration in the third tube = 20 ug/mL / 5³ = 0.16 ug/mL

When the student left the jar outside, the molecules were moving in place. Later, the molecules were moving around each other

Explanation:

There are 4 states of matter:

Solid state: In this state of matter, the particles are closely packed and they do not have any space between them. Thus, this state of matter has the highest intermolecular forces of attraction between them.

They have the lowest kinetic energy and the particles do not move freely.

Liquid state: In this state of matter, the particles are present in random and irregular pattern. The particles are closely arranged but they can move from one place to another. The intermolecular forces between the particles are less as compared to the solid state.

They have the high kinetic energy than solid and less than gases and the particles move freely.

Gaseous state: In this state, the particles are loosely arranged and have a lot of space between them. Thus, this state of matter has the lowest intermolecular forces of attraction between them.

They have the highest kinetic energy and the particles move freely.

As, the solid particles do not move freely. They move in their own place. The liquid particles are not closely packed. So, they move around the place.

Hence, when the student left the jar outside, the molecules were moving in place. Later, the molecules were moving around each other