Materials and Density

Question 1

What is a linear and non-linear relationship
between two quantities?

Answer 1

If a graph is plotted and the line of best fit is straight then we say that there is a linear relationship
between the two quantities on the x and y axes. If the line is not straight then it is non-linear.

Question 2

What is meant by a directly proportional
relationship between two quantities?

Answer 2

If a graph is plotted and the line of best fit is straight and goes through the origin then there is a
directly proportional relationship between the two quantities.

Question 3

What is the spring constant?

Answer 3

The spring constant is the amount of force needed to stretch (or compress) a material by 1 m. Its unit is N/m.

Question 4

How do you determine spring constant from
a force extension graph?

Answer 4

The spring constant is the gradient of the straight part of a force-extension graph when force is on
the y-axis and extension on the x-axis.

Question 5

What is the relationship between force,
spring constant, and extension?

Answer 5

Force = Spring Constant x Extension

Question 6

What is Hooke’s law?

Answer 6

The extension of a material is directly proportional to the force applied up to the limit of proportionality (elastic limit)

Question 7

On a force extension graph where is the limit
of proportionality?

Answer 7

The limit of proportionality on this graph is where the line stops being straight. It is the point at
which it begins to curve.

Question 8

What is meant by elastic deformation?

Answer 8

An object which is stretched (or compressed) will return to its original length when the force is removed if it hasn’t passed the limit of proportionality.

Question 9

What is meant by inelastic deformation?

Answer 9

An object which is stretched (or compressed) will not return to its original length when the force is
removed if it has passed the limit of proportionality. There will be permanent deformation.

Question 10

How do you carry out a force extension
experiment accurately?

Answer 10

Set up a clamp stand with a spring. Clamp a ruler making sure it is vertical with a set square. Make
sure the zero of the ruler is at the bottom of the spring. Add masses and record the extension of the
ruler each time. Make sure to measure the extension at eye-level.

Question 11

What is the relationship between mass,
volume, and density?

Answer 11

Density = Mass/Volume

Question 12

How do you measure the volume of regular
shaped objects accurately?

Answer 12

The volume of a regular cuboid shaped object can be found by multiplying the width, length, and
height together. Each dimension can be found accurately by repeating the measurement with a ruler
in different places along each side (and then averaging) and ensuring the ruler is at 90 degrees to the edge.

Question 13

How do you measure the volume of
irregular shaped objects accurately?

Answer 13

Fill a Eureka can to the spout with water. Add your irregular object to the water and allow the water to run
into a measuring cylinder. The volume of the water displaced is the volume of the object.

Question 14

How do you measure the mass of
an object accurately?

Answer 14

Place a digital balance on a flat surface and zero it (press the tare button) before placing the object on it.

Question 15

What do we mean by “uncertainty” in a measurement?

Answer 15

Uncertainty is the range of values in which we expect the true value of a measurement to lie.

Question 16

When a measurement is repeated, what is the uncertainty in that measurement?

Answer 16

When measurements are repeated the uncertainty in the measurement is 1⁄2 of the range. The range can be
found by taking the minimum value from the maximum

Question 17

How can particle arrangement be used to explain the differences in density between solids, liquids, and
gasses?

Answer 17

If we consider the same volume of a substance in its solid, liquid and gaseous forms then there will be much
more space between the particles in a gas than in a liquid or solid. This means that if we had the same
volume we would have much less mass of gas. Since density = mass/volume then it follows that the density of a gas is less (since mass is less for an equal volume) than a solid or liquid.

Question 18

Why does density change when a substance changes state?

Answer 18

When a substance changes state the same mass of substance will now occupy a different volume. Since
density = mass/volume it follows that density will change since volume changes.

Question 18

What do we mean by the resolution
of a measuring instrument?

Answer 18

The resolution of a measuring instrument is the smallest change that can be read from that instrument e.g. 1
mm on a ruler, or 1° on a protractor.