8th grade ReviewTOPIC: Scientific Method and ChemistryDo Now: What are the steps of the Scientific Method?Notes: (found on Ms. Harris’s Carey website)

What istheScientificMethod?

• Series of steps or procedures used to solve a problem

STEPS1. Problem

• Always in the form of a question

• What you want to solve

ProblemUnder what color light will

plants grow best?

2. Hypothesis

• Suggested answer to the problem

• HOW? Research problem

HypothesisI think the plant under green light will grow best because

plants are green.

3. Experiment

• TEST IF HYPOTHESIS IS RIGHT OR WRONG

• Gather materials• Design procedures• Record results

Experiment

Grow the plants for 5 weeks. Each is placed under a certain color light. They will get the same amount of light, & will be watered every 2 days. Their height will be measured (in centimeters) once a week.

4.Results/Observation

• Organize and analyze data

•How? Graphs, charts…

Graph•Visual display of information or data

•Organize and arrange data to be easily understood

• Independent variable = “x” axis• Dependent variable = “y” axis• Title should compare the

independent to the dependent

y-axis

x-axis

(DV)

(IV)

3 main graphs (used in science) are bar, line, & pie

•1. Bar• Comparing information collected by counting

•2. Line• Data changes over time

• 3. Circle Graph (or Pie Chart)• Different parts of a whole quantity• Slices represent percentages of the

total

2

4

6

8

10

12

Hei

ght (

cm)

PLANTS

1 2 3 4 5 6

ObservationsGrowth of plants

5.Conclusion

•Explains data •Is hypothesis right or wrong?

•Answers the question stated in the problem

Conclusion My hypothesis was wrong. Plants grow best under blue light, not green light. The plant under blue light grew 11cm while the plant

under green light grew only 2 cm.

PROBLEM

HYPOTHESIS

EXPERIMENT

OBSERVATION

CONCLUSION

People

Hate 

Elephants

On

Couches

Problem

Hypothesis

Experiment

Results

Conclusion

Repeat

Purple

Hippos

Eat

Really

Cold

Raviolis

What is aTHEORY?

•A hypothesis supported by many experiments

•Thought to be true but can be changed

What is a LAW?

• A statement that is believed to be true

ControlledExperiment

• 2 groups:•Control group•Experimental group

Group 1-Control group

• Used as a comparison

•contains the factor being tested

•Factor = variable

Group 2- Experimental group

2 typesofvariables:

• 1. Independent Variable =

• the 1 factor that’s different between experimental group and control group

• Manipulated variable

• 2. Dependent Variable =• what is measured• data or results obtained• Responding variable HEIGHT

What must bedone to makeresults of anexperimentmore reliableor valid?

• Repeat experiment• Use a larger sample

size

An investigation was done with an electromagnetic system made from a

battery and wire wrapped around a nail. Different sizes of nails were used.

The number of paper clips the electromagnet could pick up was

measured.

Independent variable:

• Sizes of nails• These were changed by the

scientist

Dependent variable:

• Number of paper clips picked up

What is the independent variable?Substance ZWhat is the dependent variable? height

To investigate the effect of a substance on plant growth, 2 bean plants of the same species were grown under identical conditions with Substance Z added to the soil of one of the plants. At the end of 2 weeks, the plant grown with Substance Z was 12.5 cm tall. The plant grown without Substance Z was 12.2cm tall. The researcher concluded that the presence of Substance Z causes the plants to grow taller.

Which setup is the control?Plant without Substance Z

What is the independent variable?WaterWhat is the dependent variable?growth

A student placed 5 geranium plants of equal size in 5 environmental chambers. Growing conditions were the same for each plant except for the amount of water each received. At the end of 20 days, plant growth was measured.

An investigation was designed to determine the effect of ultraviolet light on mold spore growth. Two groups of mold spores were grown under identical conditions, except one group was exposed only to ultraviolet light, while the other group was grown in total darkness. In this investigation, the group of mold spores grown without receiving any ultraviolet light is known as the

a. experimental variableb. hypothesisc. controld. limiting factor

CHEMISTRY

• Key points:–Matter is anything that has mass and occupies space.

–Matter can exist as a •Solid•Liquid•gas

CHEMISTRY–Elements: substances that cannot be broken down.

–Compounds: are 2 or more elements combined

CHEMISTRY–Atoms are composed of:

•Protons (positive charge)•Neutrons (neutral charge)•Electrons (negative charge)

Protons

Neutrons

Electrons

Mixture vs. compound

Pure substance –made up of just water molecules

Mix of dissolved substances such as salt, fluoride, calcium carbonate, magnesium, iron, etc…

2 types of changes

• 1. Physical change• Identity of

substance in NOT changed

• 2. Chemical Change• Chemical reaction• Form new substances with

DIFFERENT properties.• Change in color, bubbling,

light production, smoke, presence of heat, etc…

Iron + oxygen iron oxide (rust)

Raw egg cooked egg

Cake batter Cake

Physical or Chemical Change?

•Painting Wood•PHYSICAL

Physical or Chemical Change?

•Burning Paper•CHEMICAL

Physical or Chemical Change?

•Digestion of food•Both chemical and physical

Physical or Chemical Change?

•Sugar dissolving in water

•PHYSICAL

Physical or Chemical Change?

•Iron turning red when heated

•PHYSICAL

Physical or Chemical Change?

•A pond freezing in winter

•PHYSICAL

Review:1. Sand and iron particles that are

similar in size and color are mixed together in a beaker. What would be the best method of separating the particles?

a. Use tweezers to separate them. b. Add water to the mixture.c. Use a magnet to separate them. d. Pour the mixture into a filter.

2. The substances in a mixture can be separated by physical means because

a. no chemical change occurs when the substances are combined.

b. the physical and chemical properties of the substances change.

c. none of the properties of the substances change.

d. the chemical, but not the physical, properties of the substances change.

3. Is the following substance a compound or mixture?

AIR4. How would you separate a mixture of

a. sand and waterb. teac. sand and iron filings

Mixture!

Filter itFilter it

magnet