The document explains the concept of mass, which is the amount of matter in an object and remains constant, while weight varies depending on gravity. It discusses how mass is measured using balance scales and expressed in grams or kilograms, emphasizing the differences in weight experienced on different celestial bodies like the moon. Additionally, it includes practical examples of using balance scales to determine the mass of various objects.

1. Measuring Mass
By Moira Whitehouse PhD

2. Another thing scientists measure is mass. Mass
is the amount of matter or “stuff” in something
and is very closely tied to its weight.

3. Another thing scientists measure is mass. Mass
is the amount of matter or “stuff” in something
and is very closely tied to its weight.
The mass of the matter that makes up
something cannot change, but its weight can.
The reason its weight can change is that weight
depends on gravity.

4. Another thing scientists measure is mass. Mass
is the amount of matter or “stuff” in something
and is very closely tied to its weight.
The amount of “stuff” inside of something
cannot change but its weight can. The reason its
weight can change is that weight depends on
gravity.
And the amount of gravity on each moon and
planet is different.

5. Photo courtesy of NASA
The astronaut
in the picture
on the left is
wearing a
heavy space
suit and
carrying a lot
of really heavy
equipment.
However, wearing all this extra stuff on the Moon, he can
jump much higher than he can on Earth because every-
thing weighs less on the Moon than it does on Earth.

6. The mass or the
amount of stuff inside
of him, his space suit
and his equipment has
not changed, just his
weight.
The Moon has 1/6 as much gravity as Earth.
Photos courtesy of NASA
It all weighs less
because there is less
gravity on the Moon
than on Earth.

7. Similarly,
astronauts
float
weightless in
outer space
and on the
shuttle but
their mass--
the amount
of stuff in
them does
not change.
Photos courtesy of NASA

8. The mass of an object is measured:
•with a tool called a balance scale

9. •and in units
called grams (g)
and kilograms (kg).
1 kilogram = 1000 grams
1kg = 1000 g
500 g 200 g
20 g
100 g
50 g 2g10 g 5 g 1g

10. How did we get this standard unit for mass?
By using the mass of a cubed centimeter of
water.

11. How did we get this standard unit for mass?
By using the mass of a cubed centimeter of
water.

12. =

13. The two fossils in the left pan balance with
the larger sponge in the right pan. That
means that they have the same mass. Do
they have the same volume? Which has the
greater volume?

14. The metal balls in the right pan balance with
the larger sponge in the left pan. This means
that they have:
a. the same mass b. the same volume

15. These two fossils in the left pan and the steel balls
in the right pan balance on the scale. What can
you say about the mass of the two fossils and the
steel balls?

16. Notice that the
brass masses that
balance both the
metal balls and
the sponge are
exactly the same.
On the next page
you will see an
enlarged picture
of these masses.

17. So all three things—the sponge, the two fossils
and the metal balls all have the same mass.
Their mass is:
10 + 10 + 5 + 2 + 1 = 28 g

18. In the left pan of the balance scale is a quartz crystal.
In the yellow pan are the masses that balance the
mass of the crystal.
What is the mass of
the quartz crystal?

19. Yes, it would be
100 + 50 + 10 = 160 g

20. In the left pan of the balance scale is a gourd. In the
yellow pan are the masses that balance the mass of
the gourd.
What is the mass of
the gourd?

21. Yes, it is 10 + 5 + 2 + 1 = 18 g

22. In the left pan of the balance scale is a barite
crystal. In the yellow pan are the masses that
balance the mass of the crystal.
What is
the mass
of the
crystal?1g

23. Yes, it is 200 + 50 + 20 + 10 + 10 + 5 + 2 + 1 = 298
g
1 g

24. Is this scale balanced?
Which side is down—the left or the right?

25. The right side is down.
This means that the mass of the geode is
a. more than 400 g
b. less than 400 g

26. The geode has a mass of less than 400 g.

27. Is this scale balanced now?
Which side is down—the left or the right?

28. This means that the
mass of the geode is
a. more than 300 g
b. less than 300 g
This time
the left
side is
down.

29. The geode has a mass of more than 300 g.

30. Now the scale balances. What is the mass of the geode?

31. The geode has a mass of 356 g.

32. Now suppose you
see at setup like
the one on the left
with an ammonite
and 50 g in the
left pan and a
series of masses in
the right pan.
The total of the masses in the
right pan is:
100 + 50 + 10 + 10 + 5 + 2= 177g

33. 177 g177 g
Remember if the scale balances, the total
mass of all the items in the left and right
pan must equal 177 g. If this is true, then
how might you figure out the mass of the
ammonite in the left pan?

34. Your number sentence would look like this:
50 g + the mass of the ammonite = 177 g
OR
177 g – 50 g = the mass of the ammonite
177 g177 g

35. So the mass of the ammonite would be
176 – 50 = 126 g

36. So how about this one.
How would you find the mass of
the piece of coal in the left pan?
What would you do first?

37. The total mass in the right pan is
100 + 100 + 10 + 10 + 10 + 10 + 5 + 2 =
Yes, the first thing you would do would be to
figure the total mass in the right pan.
Now, what would you do?

38. Yes, you would subtract 10 g from the
total of 247 g . This will give you the mass
of the piece of coal.
247 – 10 = 237 g
The piece of coal has a mass of 237 g

39. Another kind of balance scale Is a triple beam
balance. The masses you slide along the arms of
the scale balance with the object you place on
the scale. Here is a picture of a triple beam
balance with a crystal on it.

40. You read this scale by noticing which number
each slider is on and adding those numbers
together. What is the mass of the crystal?

41. 100 + 60 + 1 = 161 g
The crystal has a mass of 161 g.

42. photo courtesy NASA
Study
science
and when
you grow
up you
may get a
chance to
go to the
moon
where:
you can
leap high
and weigh
less, but
don’t
forget,
your mass
will still
be the
same.