Praxis II general science material on the Praxis II general science exam | Questions And
Answers Latest {2024- 2025} A+ Graded | 100% Verified
matter - anything that has mass and occupies volume
made up of atoms and molecules
Lab Safety Rules (12) - 1. Report all accidents
2. Clear pathways
3. No loose hair or clothing
4. Read instructions
5. No tasting or smelling
6. Wear safety goggles
7. Do not look into a test tube while heating
8. No solids in sink
9. Clean station before leaving
10. No acrylic nails
11. Do no lift liquids above eye level
12. No eating or drinking
ions - formed when atoms, or groups of atoms, lose or gain electrons.
Metallic ions - lose some of their electrons to form positively charged ions.
non-metallic ions - gain electrons and form negatively charged ions,
physical properties of matter (9) - changes do not produce a new substance
Intensive: the same regardless of the amount
* density: m/v
,* color: The pigment or shade
* conductivity: electricity to flow through the substance
* malleability: if a substance can be flattened
* luster: how shiny the substance looks
melting and freezing point
Extensive: will change if the amount changes.
* mass: how much matter in the sample
* volume: How much space the sample takes up
* length: How long the sample is
chemical properties of matter (10) - any quality that can be established only by changing a substance's
chemical identity
* Reactivity against other chemical substances
* Heat of combustion
* Enthalpy of formation
* Toxicity
* Chemical stability in a given environment
* Flammability
* Preferred oxidation state(s)
* Coordination number
* Capability to undergo a certain set of transformations, for ex chemical combination, redox reactions
* Preferred types of chemical bonds to form, for example metallic, ionic, covalent
Pure Substance - no separation by physical means
A substance made of only one kind of matter and having definite properties.
Chemical Element - Pure chemical substance consisting of one type of atom distinguished by its atomic
number, which is the number of protons in its nucleus
,chemical compound - pure chemical substance consisting of two or more different chemical elements
that can be separated into simpler substances by chemical reactions
Solutions - molecules that are mixed up in a completely even distribution, homogenous systems
A mixture where substances are distributed evenly. Has a solvent & solute.
Mixture - Substances held together by physical forces, not chemical, can be homogeneous and
heterogeneous
Elements - pure chemical substance, one type of atom, distinguished by its atomic number (Z), the
number of protons in its nucleus
# of protons determines chemical properties
Mass number (A) is the number of nucleons (p+N) in nucleus
Oxygen most abundant on earth,
Hydrogen most abundant in universe
Elements with atomic numbers 83 or higher are inherently unstable, and undergo radioactive decay
Heavier elements were mostly produced much later, inside stars.
chemical change (11) - * Decomposition
* Neutralization (Mixing acid+base=water and a salt).
* Photosynthesis -co2 and water are changed into sugars.
* Cooking examples: cake, pancakes, and eggs/bacon
* Oxidation examples: rust or tarnishing
* Ripening examples: bananas, tomatoes or potatoes
Evidence
* Change of odor
, * Change of color
* Change in temp or energy, such as the production (exothermic) or loss (endothermic) of heat.
* Change of form (for example, burning paper).
* Light, heat, or sound is given off.
* Formation of gases, often appearing as bubbles.
* Formation of precipitate (insoluble particles).
* The decomposition of organic matter (for ex rotting food).
Dalton's atomic theory - 1. All matter is made up of atoms
2. ATOMS CAN NEITHER BE CREATED NOR DESTROYED
3. Atoms of the same element are identical
4. Atoms of different elements have different properties
5. compounds consisted of atoms of different elements combined together in a particular ratio
Work - The amount of energy transferred during an interaction
Force x Distance
transfer of energy that occurs when a force makes an object move; measured in joules
Power - Change in energy over time. Work over time. Measured in Watts or horsepower.
fusion - Creation of energy by joining the nuclei of two hydrogen atoms to form helium.
fission - The splitting of an atomic nucleus to release energy.
conversion of mass to energy - In the special theory of relativity Einstein demonstrated that neither
mass nor energy were conserved separately, but that they could be traded one for the other and only
the total "mass-energy" was conserved. The relationship between the mass and the energy is e=mc2
the speed of light squared is a very large number, a small amount of mass corresponds to a huge
amount of energy
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