Science exam answers Lesson 4

Using the correct terminology explain why a

water strider is able to stay on top of the

surface of water.

Cohesion is responsible for the surface

tension (strong attraction

between the surface particles of a fluid).

Water striders are able to stay on the surface

of the water

because of surface tension

Describe each method for determining the volume

of an object. Explain when you would use each

one.

A) We can find the volume through displacement.

We use this technique

when finding the volume

of an irregular shaped

solid object.

B) We can find the

volume by reading. We

can use this technique

for measuring liquids.

The curved line is called the meniscus.

Read the bottom of the meniscus.

Bring the eye down so it is level with the bottom

of the meniscus and read.

C) When dealing with regular shaped solids (e.g.

cube) we can use a formula e.g. V = l x w x h

Explain the mathematical relationship between

mass, volume and density.

The mathematical relationship between mass, volume, and density is that for calculating density you would use this formula:
D = m/V

If you wanted to get V (volume), you would switch with D so that it would look like this:
V = m/D

If you wanted to get m (mass), you would switch with V in this situation and change the sign from division to multiplication so that it would look like this:

m = V x D

Recall the particle theory and use it to explain the

difference between the densities of solids, liquids

and gases.

The tighter the particles are packed together in a

substance, the greater the density. The particles in

solids are tightly packed. The particles of gases are

spread apart and have the least density.

What units can be used to measure density?

Mass (grams) per unit volume (Liters/cm^3)

A characteristic property is one that is specific to

a particular substance and can be used to identify

it. Why is density considered a characteristic

property?

Each pure substance has a specific density.