CHAPTER 1World of Physical Science

Section II – The Scientific Method

Though the scientific method has several steps, real scientists may take the steps in different order, skip steps or repeat steps in order to try to find the answer to a question.

Ask a question (Step 1)

1. Questions are usually asked after scientists have made a lot of

observations.

a. Observations are any use of the senses to gather information. (Sometimes this is called Qualitative data)

b. Measurements are observations made with instruments.(Sometimes this is called Quantitative data)

From a Hypothesis (Step 2)

1. A Hypothesis is a possible explanation or answer to a question.

a. Scientists generally form hypotheses that can be tested. Where observations and can be made and information can be gathered.

Hypothesis that cannot be tested are neither right or wrong because there is no way to support or not

support them.( these hypothesis exist but are neither right or wrong but

are not considered valid, because to be valid, they must be testable and supported by evidence that means proven right!)

Test the hypothesis (Step 3)

1. After a hypothesis is formed, you must test it to determine if it is a reasonable answer to your

question.

2. One way to test a hypothesis is a controlled experiment.

a. A controlled experiment hasIndependent variable- the part of the experiment you

manipulate.

Dependant variable – the part of the experiment that changed because of what you changed.

Controlled factors- What other things in the experiment must be held the same so that it does not mess up the results.

Analyze the results (Step 4)

1. All of the collected data needs to be studied to see if the test supports

the hypothesis.

2. Putting information into tables and graphs helps to make the relationships between the information easier to see.

Draw conclusions (Step 5)

1. After looking at the data you must decide if the information supports your hypothesis or not.

a. If it does support the hypothesis you can ask

further questions.

b. If it does not support the hypothesis you can check you results for errors or modify your hypothesis.

Communicate results (Step 6)

1. Most scientist publish their results in magazines and academic papers.

2. Most students publish results in a lab paper.

REMEMBER-NOT all scientists use the scientific method.

Scientific Method Video Courtesy: http://www5.unitedstreaming.com/index.cfm

DEVELOP A MEMORY TRICK

• A

• H

• T

• A

• C

• C

Lab design Imagine you are conducting an experiment in which you are testing the effects of the height of the ramp on the speed at which a toy car goes down the ramp.

Hypothesis - what is the relationship you are trying to discover?

Independent variable- the part of the experiment you manipulate.

Dependant variable – the part of the experiment that changed because of what you changed.

Controlled factors- What other things in the experiment must be held the same so that it does not mess up the results.

Lab design

A doctor has developed a new headache medicine. How should he set up his test trials to figure out if it works?

Hypothesis

Independent variable

Dependant variable

Controlled factors

Lab designMed 1 Med 2 Med 3 No med

People with headaches out of 100

5 20 30 20

What to the results tell you about the different medicines?

Why is a group with no medicine included?

Building scientific knowledge.

1. Answers in sciences are rarely final answers. As our understanding

grows our ideas about the world around us changes.

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2. A Scientific Theory is a unifying explanation for a broad range of hypothesis and observations that have been supported by testing (Often explains why). It can be changed as new observations are made and new hypothesis are tested.

3. A Scientific Law is a summary of many experiments and observations. They tell you how things work. They only explain what happens, not why.

• What is the difference between a theory and a law?

• A theory is based on supported hypothesis's where as a law is based on the results of the experiment instead of the hypothesis

• A _____ is a summary of many different experimental results and observations

• Law

III. USING MODELS IN SCIENCE (p.20-23)

A. What is a model?1. A model is a representation of an object or

system. Including scientific ideas and objects

2. They can be used to make predictions or explain observations.

3. Models are never exactly like the object or system.

4.They can be tools used to conduct an investigation

5.They can illustrate theories

In what other ways might models be helpful?

IV. MEASUREMENT AND SAFETY IN SCIENCE (p.24-27)

A. The International System of Units

1. It helps scientists compare their information.

2. All units are based on the number 10.

SI Video Courtesy: http://www5.unitedstreaming.com/index.cfm

3. Length – The Meter is the basic unit of length. Other SI units of length are larger or smaller than meters by multiples of 10. The tool used to measure length is a meter stick or ruler

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1. 10 meters is equal to how many cm? 1000cm How many mm? 10,000mm

2. 500 meters is equal to how many km?0.5 km3. 500 cm is equal to how many meters?5 metersHow many mm? 5000mm How many km?0.005 km

4. Volume- the amount of space that something occupies. The tool used to measure volume is a graduated cylindera. Volume of liquids is expressed in Liters (L).

b. Liters are based on the meter, 1000 liters will fit into a cubic meter.

c. A milliliter (ml) will fit in to a box one centimeter (cm) on a side.

1. How many ml in one cm3 ? one

2. How many ml in a liter? 1000

d. Volumes of solid objects are expressed in cubic meters (m3) smaller objects are expressed in cm3 or mm3.

e. To find the volume of a rectangular shape, multiply length x width x height.

f. To find the volume of an irregularly shaped object, measure how much liquid it displaces.

What is the label or unit for the volume of a rock?cm 3 because it is a solid

What is the label for a volume of gasoline? ml because it is a liquid

What is the volume of a box that is 3 cm long, 10 cm tall and 3 cm wide?3 x10 x3 = 90cm3

There is 30 ml of water in a graduated cylinder. After a rock is placed in the cylinder the water level measures 45ml. What is the volume of the rock?

15 cm3

5. Mass- the amount of matter something is made of. The kilogram is the basic unit of mass. Grams are used to measure smaller objects. 1000 kg is a metric ton.

The tool used to

Measure mass is

A balance.

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6. Temperature- how hot or cold something is. Scientist usually uses the Celsius scale (Co) to measure temperature. Kelvin is the SI unit of temperature. Fahrenheit is the most common unit of temperature in the United States.

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B. Derived Quantities- formed from a combination of other measurements.1. Area- a measure of how much surface an object has. It is determined by multiplying length time’s width.2. Density- is mass per unit volume

D = m/v

(Demonstrate triangle equation)

1. A cereal box has the dimensions of 27 cm x19cm x 6 cm. What is the area of the front of the box. ( Hint; how can you tell which numbers to use?)

27cm x 19 cm =513cm2

2. What is the volume of the box?27cm x 19 cm x 6 cm = 3078 cm3

3. If the box has a mass of 340 g what is the density of the box?340g / 3078 cm3= 0.110g/cm3 ( three significant figures)

C. Safety rules-

1. Pre read labs and read the safety information on p.622.

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