Metric System

Mass & Weight• What's the difference?• Units & Measurement Tools• Reading a Balance

ReviewReview

What are two advantages to the metric system?

1. Scientists can share & compare data2. All units are based on the number 10.

ReviewReviewMatch the phrase with the correct term.Match the phrase with the correct term.

1. The SI unit for Volumee) liter

2. The SI unit for Lengtha) meter

3. The SI unit for Massb) gram

4. The SI unit for Temperaturec) Celsius

5. The SI unit for Weightd) Newton

a) Meter

b) Gram

c) Celsius

d) Newton

e) Liter

SI PrefixesSI Prefixes

MassMass

• Amount of matter in an object– how much stuff an object is made of

• Compare a basketball & a bowling ball.• Even thought they’re about the same size

(volume!), they have totally different masses.

MassMass

• Units: gram (g) or kilogram (kg)

• Think About– 1 science book = 1.3 kg– 1 large paperclip = 1

gram – 1 ml of water = 1 gram

MassMass

Measurement Tool: triple-beam balance

• The object’s mass is compared to the balance’s weights

Labeled Balance

Using a Triple Beam Using a Triple Beam BalanceBalance

• We’re going to use these in the lab today. PLEASE BE CAREFUL. They break really easily.

You Try It! You Try It! Reading a BalanceReading a Balance

1. What does this balance read?155 grams

You Try It!You Try It!

2. What does this balance read?323.5

grams

You Try It!You Try It!

3. What does this balance read?201.9

grams

MassMass

Is it affected by gravity?• NO!!!• Whether on the moon or on Earth,

your mass remains the same.

WeightWeight

• The downward force of gravity acting on an object– On Earth, the word “weight” refers to Earth’s

gravitational force on an object. – But “weight” can be applied to any amount of

gravity on any planet

WeightWeight

• Unit: Newton (N) or Pound (lb)

• Think About:– A medium apple = 1 N

– A paperback book = 1 lb

• Measurement Tool: spring scale

WeightWeight

Is it affected by gravity?• YES!!!• Weight is a measure of the force of

gravity.• More gravity? More weight!• Less gravity? Less weight!

Your Weight on other Your Weight on other WorldsWorlds

If you weigh 100 pounds…If you weigh 100 pounds…

Object Gravitational Pull (N)

Your Weight (lb)

Mercury 0.378 100 lb x 0.378 = 37.8

Venus 0.907

Luna 0.166

Mars 0.379

Jupiter 2.36

Pluto 0.067

Our Sun 27

Your Weight on other Your Weight on other WorldsWorlds

Object Gravitational Pull (N)

Your Weight (lb)

Mercury 0.378 100 lb x 0.378 = 37.8

Venus 0.907 90.7

Luna 0.166 16.6

Mars 0.379 37.9

Jupiter 2.36 236

Pluto 0.067 6.7

Our Sun 27 2700

Finding the Mass of a LiquidFinding the Mass of a Liquid

• As a group, discuss the following. How do you find the mass of 50 mL of water?

• Can you come up with 3 ways?

• Record your idea in the space.

Finding the Mass of a LiquidFinding the Mass of a Liquid

1. Find the mass of an empty container, then with water, subtract

2. Place the container on the balance, calibrate it, then find the mass of the water

3. 1 ml water = 1 gram, so 50 ml = 50 grams