The Physical Sciences

Chapter One: What Physics and Chemistry are About

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1.1 The Physical Science in Your Life

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1.2 Describing the Physical World

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1.3 Energy, Matter, and Change

Investigation 1B

Measuring Mass and Length •

How do scientists measure mass and length?

1.2 Describing the Physical World

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Energy

is how the universe changes. • A fast ball has more energy than a slow ball.

1.2 Describing the Physical World

• Up-down, right-left, and forward backward are three directions of space.

• To completely understand the motion of a ball we need to know its exact path.

1.2 Describing the Physical World

• Time is our reference for understanding change. • As time goes on, each change causes other changes, which cause still more changes.

1.2 Mass

• Mass is measured in

kilograms (kg) .

One gram (g) is one-thousandth of a kilogram.

How many grams is each item above?

1.2 Mass

• For small amounts of mass, the kilogram is too large a unit to be convenient.

• In the laboratory you will usually measure mass with a

balance

. • The balance displays mass in grams.

1.2 Length and Distance

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Distance

is the amount of space between two points.

• Distance is measured in units of length.

1.2 Length and Distance

• Some of the commonly used units of length include inches, feet, miles, centimeters, kilometers, and meters.

1.2 Length and Distance

• The names of units in the metric system are based on multiplying by ten.

• Almost all fields of science use metric units because they are easier to work with.

1.2 Measuring Length

• For ordinary lengths you must measure in the laboratory a

meter stick

is the most convenient tool to use.

• For very small lengths, such as the size of a bacteria, scientists use measuring instruments that fit into a microscope.

1.2 Time

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Time

has two important meanings.

–

What time is it?

–

How much time?

1.2 Time

• •

Units for time include:

– – –

seconds minutes hours The second is the basic unit of time in both the English and metric systems

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1.2 Mixed units of time

• Time is often expressed in mixed units. • This timer shows the time for a race as 2 hours, 30 minutes and 45 seconds.

1.2 Mixed units of time

• A microwave oven can program time in either mixed units (minutes and seconds) or in a single unit (seconds).

Explain how 1:30 and 0:90 will result in the same cooking time.