You have probably heard the old trick question,

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You have probably heard the old trick question,

• Which is heavier?
• a pound of feathers
• or
• a pound of bricks?

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Why do you think so many people blurt out the
answer bricks?

• Why do the bricks seem heavier?

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Now take a look at the empty balance

• Imagine that on the right side of the balance you
  are going to place a pound of bricks. How much
  space would they occupy?
• Now, imagine placing a pound of feathers on the
  left side. How much space would they occupy?
• Take a minute to sketch what you have imagined.
• This is not an art contest you can simply use a
  rectangle to represent the space occupied by the
  bricks and another rectangle for the space
  occupied by the feathers.
• Make sure you label your rectangles.

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So what is the biggest difference between a pound
of feathers and a pound of bricks?

• Space occupied by each of them

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2.1 Measuring mass

• Mass describes the amount of matter in an object.
  
• The SI unit for mass is the kilogram (kg).
• The kilogram is too large a unit to be convenient
  for small masses.

One gram (g) is one-thousandth of a
kilogram. What is the estimated mass of ONE zinc
nut?
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2.1 Matter

• Matter is anything that has mass and takes up
  space.
• All matter has mass.
• Steel, plastic, rubber, and glass are different
  kinds of matter.

A car has a lot more of each kind of matter than
a bike.
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2.1 Mass and weight are different

• We tend to use the terms mass and weight
  interchangeably, but they are not the same thing.
  
• Mass is the amount of matter in an object.
• Weight is a measure of the pulling force of
  gravity on an object.

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2.1 Mass and weight are different

• A 2.3 kg bag of flour has a mass of 2.3 kilograms
  no matter where it is in the universe.
• The weight of the bag of flour is less on the
  moon.

The 5 lb bag of flour on Earth weighs only .8 lbs
on the moon!
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2.1 Volume

• Volume is the amount of space an object takes up.
• The fundamental unit of volume in SI is the cubic
  meter (m3).
• More convenient smaller units are cubic
  centimeters (cc or cm3), liters (L) and
  milliliters (mL).

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2.1 Volume

• Measuring the volume of liquids is easy.
• Pour the liquid into a graduated cylinder and
  read the meniscus at eye level.

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Mass and weight

• Can someone tell me the difference between mass
  and weight?
• mass is a measure of the amount of matter in an
  object, whereas
• weight is a measure of gravitational force
  between an object and (in our case) Earth.

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2.1 Displacement

• You can find the volume of an irregular shape
  using a technique called displacement.
• Put the irregularly shaped object in water and
  measuring the amount of water displaced.

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2.1 Comparing mass and volume

• Mass and volume are two different properties of
  matter.
• Size does not always indicate an objects mass!
• How the matter is packed into space is more
  important.

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