nj ask review p hysical s cience 8 th grade science
TRANSCRIPT
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
BS
TAN
CE V
S.
MIX
TU
RE
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.