The Scientific MethodThe Scientific MethodMr. Luis A. Velazquez

What is the scientific method?

• Is a step by step process to understand nature.

• Scientists use an experiment to search for cause and effect relationships in nature.

• In other words, they design an experiment so that changes to one item cause something else to vary in a predictable way.

What are the steps in the scientific method?

• Define the problem • Gather information • Make an hypothesis• Test your hypothesis• Review your results • Make a conclusion

• In an experiment these changing quantities are called variables, and an experiment usually has three kinds:

• independent• dependent• control

What are variables?

The control variable

• Controlled variables are quantities that a scientist wants to remain constant, and he must observe them as carefully as the dependent variables. Why?

• Most experiments have more than one controlled variable.

• Some people refer to controlled variables as "constant variables."

The Independent Variable

• The independent variable is the one that is changed by the scientist.

• In an experiment there is only one independent variable.

The dependent variable

• The dependent variable changes in response to the change the scientist makes to the independent variable.

• The number of dependent variables in an experiment varies, but there is often more than one.

Examples:

• “For example, if you open a faucet (the _________ variable), the quantity of water flowing (__________ variable) changes in response-the water flow increases.”

How to identify the dependent variable?

• To be predicted• The response variable• The outcome• A variable that is not under the

experimenter's control.

Difference between Variables

• Dependent– One or more– Output– Response var– Results and

data– Not controled

– Effects

• Independent– Only one– Input– Manipulated

var– Is under the

control of the Experimenter

– Cause

• The cause• The input• The manipulated variable• The variable that is changed on

purpose in an experiment.

How to identify the independent variable?

• if we want to measure how much water flow increases when we open a faucet, it is important to make sure that the water pressure (the controlled variable) is held constant.

• That's because both the water pressure and the opening of a faucet have an impact on how much water flows.

• If we change both of them at the same time, we can't be sure how much of the change in water flow is because of the faucet opening and how much because of the water pressure.

• Most experiments have more than one controlled variable.

The SI Unit SystemThe SI Unit SystemMr. Luis A. Velazquez

PREFIX SYMBOL FACTOR

yotta Y 1024

zetta Z 1021

exa E 1018

peta P 1015

tera T 1012

giga G 109

mega M 106

PREFIX SYMBOL FACTOR

kilo K 103

hecto H 102

deka D 101

deci d 10-1

centi c 10-2

milli m 10-3

micro 10-6

nano n 10-9

pico p 10-12

femto f 10-15

atto a 10-18

zepto z 10-21

yocto y 10-24

Prefix• Kilo 10x 10 x 10 = 1000 = 103

• Hecto 10 x 10 = 100 = 102

• Decka 10x1 = 10 = 101

• deci 1/10 = 0.1 = 10-1

• centi 1/100 = 0.01 = 10-2

• milli 1/1000 = 0.001 = 10-3

1x1 = 1 = 100

How to remember?

• King • Henry • Died

• Drinking• Chocolate • Milk

Basic unit

K

H

D

dc

m

mass, length, volume

Kilo

Hecto

Decka

deci

centi

milli

Basic Unit

Grams, Liters, meter

Left

Right

Practice Problems

Kilograms are bigger than Grams So you need to multiply this means you

move the decimal to the right How many times? 3

5 Kg =_______ g

Answer 5000

5000

Practice Problems

centigrams are smaller than grams So you need to divide this means you

move the decimal to the left

How many times?2

.045 cg =_______ g

Answer .00045

.00045

Practice Problems

Dekagrams are bigger than grams So you need to multiply this means you

move the decimal to the right

How many times?1

36 Dg =_______ g

Answer 360

360

Practice Problems

milligrams are smaller than Kilograms So you need to divide this means you

move the decimal to the left

How many times?6

7 mg =____________ Kg

Answer 0.000007

0.000007

Practice Problems

Liters are bigger than milliliters So you need to multiply this means you

move the decimal to the right.

How many times?3

9 L =_______ mL

Answer 9000

9000

Answer tofollowing Problems

• 35L = .035 KL• 46 g = .46 Hg• 0.000015mg = .0000000015 Dg• 9.53 mm = .00953 m• 7.908 cL = .07908 L• 0.521 Hm = 5210

cm

• 35L = .035 KL Liter are smaller than Kiloliters so

you divide or move your decimal to the left.

You move your decimal to the left three times

The answer is .035 KL

• 46 g = 0 .46 Hg

Grams are smaller than Hectograms so you divide or move your decimal to the left.

You move your decimal to the left two times .

The answer is 0.46Hg or .46 Hg

0.000015mg = .0000000015 Dgmilligrams are smaller than Decagrams

so you divide or move you decimal to the left.

You move your decimal to the left four times.

The answer is .0000000015 Dg

9.53 mm = .00953m millimeters are smaller than meter

so you divide or move you decimal to the left.

You move your decimal to the left three times

The answer is .00953 meters

• 7.908 cL = .07908L centiliters are smaller than Liters

so you divide or move you decimal to the left.

You move your decimal to the left two times.

The answer is .07908 Liters

0.521 Hm = 5210 cm

Hectometer are bigger than centimeters so you multiply or move you decimal to the right.

You move your decimal to the right four times.

The answer is 5210 cm