NJ ASK REVIEWPHYSICAL SCIENCE8th grade science

MATTER

Matter – anything that has mass and takes up space

Some types of matter are called

Substance –

Every form of matter contains bothproperties.

substances

A single kind of matter that is pure.

physical and chemical

*substances have the same type of make up and properties no matter where it comes from – Examples:Salt, sugar and water

PHYSICAL PROPERTIES

A characteristic of a pure substance that can be observed without changing it to another substance.

Physical properties can be observed by

Examples of physical properties:

touching or looking at a substance.

•Melting/freezing point•Hardness•Texture•Color

CHEMICAL PROPERTIES

A characteristic of a pure substance that describes its ability to change into different substances.

Chemical properties can only be observed when

Examples:

a substance combines with something else and forms a new substance.

•Flammability •Rusting

CHEMISTRY IS ALL ABOUT HOW MATTER CHANGES!

Physical Change - any change in the form or appearance of matter.

A physical change change the substances

Examples:

DOES NOTchemical makeup

•Crushing•Ripping•Breaking•Chopping•Blending•Dissolving

Chemical change - When one substance changes into one or more different substances

Atoms are rearranged not taken away or added!

Example:

Keep in mind… during a chemical or physical changewe call this

CHEMISTRY IS ALL ABOUT HOW MATTER CHANGES!

•Oxidation: rusting (this occurs when iron and oxygen mix)

matter cannot be created or destroyed the law of conservation of mass

UNDERSTANDING CHEMICAL REACTIONS

We know that a chemical change occurs when

We can also call this a

Chemical Reaction -

one or more substances change into a new substance.

chemical reaction

A process in which atoms of one or more substances rearrange to form one or more new substances.

SIGNS OF A CHEMICAL REACTION

HOW CAN WE DESCRIBE A CHEMICAL REACTION?

By using

Chemical equation - a description of a reaction using element symbols and chemical formulas.

a chemical equation

PARTS OF A CHEMICAL EQUATION

Reactant –

Yield (or produces) –

Product –

Subscript –

the starting substances in a chemical reaction (belong to the left of the arrow)

the arrow used to represent the chemical reaction taking place.

the substances produced by the chemical reaction (belong to the right of the arrow)

Describes the number of elements in a compound. Belongs after the atom it represents and is written small. **If there is no subscript it means there is only one atom of that element**

LABEL ALL PARTS OF THE FOLLOWING CHEMICAL EQUATION

CHEMICAL BONDS CONTAIN ENERGY

Chemical bonds contain

Some chemical reactions more energy than they absorb.

Some chemical reactions more energy than they release.

chemical energy

release

absorb

ENDOTHERMIC VS. EXOTHERMIC REACTIONS

Endothermic Reaction –

Exothermic Reaction -

chemical reactions that absorb thermal energy.

chemical reaction that releases thermal energy.

AFTER TALKING ABOUT ATOMS THAT ARE CHEMICALLY COMBINED…

Chemical bonds Covalent bonds –A chemical bond formed when two

atoms share electrons.

Ionic bonds - Atoms transfer (give or take) valence electrons to reach stability

HETEROGENEOUS MIXTURE

A mixture in which substances are not evenly mixed.

Examples:

•Salad•Granite•Soil

HOMOGENEOUS MIXTURE

A mixture in which two or more substances are evenly mixed on the atomic level but NOT bonded together.

Examples:

Another name for “homogeneous mixture” is

•Air•Soda

solution

MIXTURES CAN BE SEPARATED

Mixtures can be separated because

Mixtures can be separated by using physical methods including: Filtering

Boiling

Magnetism

they are not bonded together

separation by size

separation by boiling point

separation by magnetism (for objects attracted to magnets)

SU

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TAN

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MIX

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ACIDS AND BASES… NECESSITIES TO OUR EVERYDAY LIFE!

The pH scale is used to measure how and a substance is.

The pH scale is a range of values from to .

ACIDICBASIC

0 14

PH SCALE

Something that is neither acidic or basic is

Neutral is the pH of: Any value below the pH of 7 is: Any value above the pH of 7 is:

**Label the pH scale on your paper**

NEUTRAL

7 (water) ACIDIC

BASIC

ACIDS

Chemicals in which the positive ion is a hydrogen atom Ion – an atom or group of atoms that has a

positive or negative charge

Properties•Tastes sour•Reacts with metals

•Reacts with carbonates – (causes bubbles to appear)•Turns litmus paper red

**Litmus is a colored chemical which can change from red to blue and back again – the color it changes depends on whether the substance is basic or acidic.

•Corrosive – (eats away other materials)

BASES

Substances with a negative ion called Hydroxide

Properties:•Tastes bitter

•Slippery•Turns litmus paper blue

FROM EXPERIENCE NAME SOME ACIDS AND BASES:

ACIDS BASES

pH = O

pH = 2

pH = 3

pH = 4

NEUTRAL

pH = 8-9

pH = 10

pH = 12

pH = 14

PH SCALE

The pH scale expresses the concentration of ions in a solution.

Low pH tells you:

High pH tells you:

HYDROGEN

THERE IS A HIGH CONCETNRATION OF HYDROGEN IONS.

THERE IS A LOW CONCETNRATION OF HYDROGEN IONS.

BEING SAFE

In order to handle acids and bases safely you need to know their and

Concentration –

A reaction between an acid and a base is called:

Neutralization -

pH CONCENTRATIONThe amount of one material in certain volume of another material.

NEUTRALIZATION

A reaction of an acid with a base creating a solution that is no longer as acidic or basic as the original solution.