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Chapter 2Measurement and Calculations

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Chapter 2Measurement and Calculations

The marshmallow test

The marshmallow test study description and conclusionshttp://www.youtube.com/watch?v=amsqeYOk--w&NR=1

http://youtu.be/QX_oy9614HQ

Qualitative: Use descriptions to explain data Ex: small, white, puffy, smells good,

quiet, wiggly

Quantitative: Use numbers to describe data Ex: 4 cm, 5.30 grams, 15.65 minutes

Observing and Collecting Data2.1 The Scientific Method

System – a specific portion of matter in a given region of space that has been selected for study during an experiment.

2.1

Example: In Marshmallow Test, the system is the child, the marshmallow, the plate, and everything in the room.

Surroundings – everything outside of the system.

Example: In the Marshmallow Test, the surroundings are everything outside of the room.

2.1 The Scientific Method – a review

A hypothesis is a testable statement(it really is not just an educated guess)

A hypothesis is often written as an if – then statement

Formulating Hypotheses2.1

Ex. If phosphorus stimulates plant growth, then plants treated with phosphorus fertilizer should grow faster than plants not treated with phosphorous fertilizer (all other variables held constant).

Sometimes we add more detail to the hypothesis:• Plants that receive more phosphorus should

grow faster than those that receive less phosphorus.

Testing Hypotheses2.1

In Science, there is a commitment to follow the evidence, wherever it leads. If a hypothesis is not supported by data, it must be rejected.

There must also be a willingness to accept that new evidence may require us to modify or change our ideas about what we thought to be true.

So, was the hypothesis about phosphorus fertilizer correct?

Theorizing2.1

In everyday language, the word “theory” is often misused when a more accurate term would be “hypothesis.”

Example: I have a theory that it always rains after I wash my car.

This is really a hypothesis. It has not been, but could be tested. A theory would have already been vigorously tested, generated consistent results, and would offer an explanation of why the event occurs.

Theorizing2.1

A theory is a broad generalization that explains a body of facts or observations.

Theories are well documented and proved beyond reasonable doubt.

Scientists continue to tinker with the component parts of each theory in an attempt to make them more exact. Theories can be tweaked, but they are seldom, if ever, entirely replaced.

Always contain two parts number unit

Both parts must be present for the measurement to be meaningful.

Quantitative Measurements

2.2 Units of Measurement

SI Measurement2.2

A quantity is something that has magnitude, size or amount.The units of measurement must be standardized for the measurement to make sense to everyone.

A standardized system of measurement is one in which everyone agrees upon the size of the unit. Early systems of measurement were based upon the size of the king’s foot, or length of arm, for example.

But this type of system has problems:•What happens if you want to communicate

measurements to someone in another country?•What happens when you get a new king?

2.2

Mass- • a measure of the amount of matter in an object• standard unit is the kilogram (but we often use grams)• not the same as weight

Remember this?Weight is a measure of the pull of gravity on the object, so the stronger the gravitational pull, the higher the weight.

SI Base Units

2.2

Length- • a measure of distance• standard unit is the meter • we often use mm, cm

SI Base Units

2.2

Volume- • the amount of space an object takes up

• standard unit for liquids is the liter (L) but we often use mL (1/1000 of a liter)

• we also use cm3 (for solids)

SI Base Units

It is very helpful to know that 1 mL and 1 cm3 are equal volumes

1 cm3 = 1mL

Used for solids Used for liquids

2.2

The SI Units of Measurement (le Système International, SI)

You do not need to be concerned with Amperes and candelas this year

2.2

The SI Units of Measurement (le Système International, SI)

Prefixes are added to these base units to show quantities in larger or smaller amounts.

(you will have the ones you need on a handout)

2.2

Here are a few of them:Tera T 1012 1 000 000 000 000Giga G 109 1 000 000 000Mega M 106 1 000 000Milli m 10-3 1/1000Nano n 10-9 1/1 000 000 000