Chapter 2: Thinking Like a ScientistFoundationsMs. Johnson

Objectives• Science is studied by using observations and

inferences.• Observations are made by the senses.• Inferences are conclusions or predictions based on

observations.• Larger numbers of observations produce better

inferences.• Inferences may be tested through experiments.• Limiting the number of variables in an experiment

produces better inferences.• Graphing observed data aids us in making

inferences.

Vocabulary•Observation•Inference•Variables•Experimental Sample•Control•Line graph•Bar graph

Observation and Inference• The primary learning tools of the scientist are:

▫Observation: anything we notice though one of our five senses.

▫Inference: a conclusion or prediction based on an observation or a series of observations.

• For example, if you walk into a room and say, “It stinks in here! Something must have died!”▫You have made both an observation using your

sense of smell, and an inference based off that sense.

• Once an inference has been made, it is generally tested through further observations.

Observation or Inference?1. The sun rose at 6:30 this morning

Observation

Observation or Inference?2. The plant on the right is growing more because it has been receiving more water.

Inference

Observation or Inference?3. Dinosaurs died out when they could not adapt to the changing climate.

Inference

3 Observations and 2 Inferences?

Making Valid Inferences• Make careful

observations.• Base an inference on

a large number of observations.▫The greater the

number, the more likely the inference is to be correct.

• Limit the number of variables.▫Variables: changeable

conditions that can affect observations.

▫An experiment that tests the limit of just one variable is called a controlled experiment. Control: the portion of an

experiment that is not changed Experimental sample: the

portion of an experiment that is changed

Organizing Observations•When we want to draw an inference

based on a large number of observations, it is important to organize our observations in a logical way.▫Bar Graphs▫Line Graphs

•The next slide will show you how organizing observations is important.

Time Needed to Collect 50mL of Oxygen from Identical Solutions of Hydrogen PeroxideTable A

Run Temp. (Celsius)

Time (minutes)

1 30 8.0

2 50 2.1

3 10 33.0

4 20 16.0

5 40 4.1

Table B

Temp. (Celsius)

Time (minutes)

10 33.0

20 16.0

30 8.0

40 4.1

50 2.1

When comparing these two tables, you can see that table A has more data because it shows the order these observations were made.However, that extra data is not important or needed.

In Table B, it is easier to observe a trend and draw inferences and create data tables.

Using Line Graphs• By graphing our observations,

we are able to infer values that lie between and beyond our measured points.

• The greater the number of observations, the more reliable the inferences.

• Plotting the data from Table B, we can plot the points and create a line graph of temperature vs. time.

• The 5 points show the observations, all other points along the graph are inferences.

Using Bar Graphs• Bar graphs are also used to help organize and

illustrate observations.• They are used to make clear and dramatic

comparisons (in line graphs, the x- and y-axis show amounts, in bar graphs only the y-axis shows amounts).

Using Bar Graphs

Colum

bus, O

H

Cincin

nati,

OH

Hon

olul

u, H

I

Seattl

e, W

A

0

10

20

30

40

50

60

70

Average Annual Rainfall (inches)

Average Annual Rainfall (inches)

Inches

per

year

With the bar graph, we can quickly observe which city has the most rainfall and which has the least.

Chapter 3: Science Safety ProceduresFoundationsMs. Johnson

Objectives• Many chemicals found at home and in the laboratory can

be dangerous if not used properly.• Dangerous chemicals include those that are toxic

(poisonous), flammable (burn), and/or caustic (destroy skin).

• Never perform experiments without a supervising adult’s permission.

• When working in the laboratory, observe proper safety precautions, including eye protection, safe clothing, and proper equipment.

• In case of an accident, inform the teacher immediately.• Never clean blood spills yourself. Report these to the

teacher.

Vocabulary•Vapors•Flammable•Toxic•Caustic•Corrosive

Safety at Home•Household substances that can be hazardous

include: bleach, ammonia, lye, paint thinner, some kinds of glue, and all medications.

•The most dangerous are those that give off Vapors: fumes or gases▫Vapors can be flammable, toxic, or both.

•Flammable: a substance that burns quickly▫Ex: gasoline and paint thinners (these

substances explode from the touch of a spark)

Safety at Home cont.•Toxic: substances that are poisonous.

▫Breathing these can cause serious illness or death

▫Ex: ammonia, paint thinners, and some kinds of glue

•Toxic and flammable substances should be used in well-ventilated areas and away from flames.

Safety at Home cont.•By law, these types of chemicals have to

have a warning label.

Safety at Home cont.•Some substances are dangerous to touch.

▫Caustic: substances that can destroy living tissue such as skin

▫Corrosive: substances that eat through skin, clothing, and most metals Ex. lye found in oven cleaners and drain

openers, acid from car batteries•Avoid combining household chemicals

(they can sometimes form more dangerous chemicals or cause explosions).

Safety at Home cont.•Be careful also around pressurized cans

(hair spray, spray paint, whipped cream cans) because these cans can explode if exposed to heat.

•All chemicals and drugs should always be stored out of the reach of children and pets.▫Ex. aspirin is generally a safe drug, but

children have died from overdose because they did not know what they were.

Preparing Lab Work• To avoid accidents in labs, take necessary

precautions:▫Tie back long hair, wear closed shoes, and clothes

that cover▫Wear goggles and lab coats▫Avoid dangling jewelry (earrings and necklaces)

• NEVER bring food and drink into the laboratory.• Pay attention to instructions (especially where

chemicals are involved).• Know where safety equipment, eye-wash station,

fire extinguisher/blankets, and glass disposal bins are.

Working With Chemicals•With chemicals there is always danger of

explosions, breakage, spills, and spattering. If you spill, immediately wash it away with cool water.

•If you need to smell an odor, never put the substance right under your nose; hold it away from your face and waft it towards you.▫NEVER taste a chemical.

Working With Heat• Three common methods for heating:

▫Hot Plate Always assume it is too hot to the touch- you can

never tell whether it is on or off▫Alcohol Burner▫Bunsen Burner

• Use the right tools for holding hot items▫Test tube holder (come in a range of sizes)

• Heated chemicals can splatter, so make sure to wear safety goggles, never point the container towards you, and only heat liquids in an open container

Safe Use of Electricity• Use commonsense safety rules when working with

electricity.▫Check for damaged wires

Don’t use electrics with frayed or broken wires▫Always unplug electrics before cleaning or repairing

them.• Never pull a plug out by the cord, pull from the plug

itself.▫Don’t‘ touch the metal prongs either; sometimes they

can still carry an electrical charge after being unplugged.

• Never handle electronics around water or if your hands are wet.▫Keep all plugs, cords, and appliances away from water

After the Experiment•Carefully clean and return all equipment

to the appropriate place•Wash your hands (especially when

working with chemicals or living things)•Clean your station before you leave

Working With Sharp Tools•NEVER touch the sharp edges of tools.

▫Store them in drawers or cabinets•If you or a classmate gets cut, NEVER touch

the blood directly.▫Assume all blood is dangerous▫Report any cut to a teacher immediately

•Don’t clean up the blood yourself•Don’t touch the instrument that caused the cut•Broken glass is the most common causes of

injury in labs

Questions?