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if the scientist used something positive instead of negative

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Food
1,density:

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Photon is inside the atomic ,firework though endothermic  reaction, rising from ground state to the excited state,also the energy achieve the energy level,and then it can make entertaining light.

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group: two or more atoms bound together as a single unit and forming part of a molecule.
protons: A proton is an atomic particle that has a positive electrical charge.
atomic number:the order of an element in Mendeleyev's table of the elements; equal to the number of protons in the nucleus or electrons in the neutral state of an atom of an element.
metals:any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc.
In this paper,the research progress on CS-AAS at home and abroad in recent years,and the application of CS-AAS in determination of nonmetals(sulfur and halogens) and solid sample injection were reviewed.

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#4 --midterm#
1:In general metal are glossy  most of the metal is silver; Non-metallic are not glossy. And color is also varied.
2:Most metals is malleable, and they can heat and conduction;And non-metallic are not ductility, they can't heat and cannot conduct electricity.
3:Generally, the density of the metal is bigger, high melting point; And non-metallic's density is small, low melting point.
Examples:
metal:Iron scoop
non-Metal：paper

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Write your answer

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#9

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For example,

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endothermic is get the hot energy in,exothermic is make the hot energy goes out.

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when covalent  bond occur, they share valence electrons ,but the       ionic bond occur one atom takes another's  valence electrons fully.

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In chemistry and physics, an element is a substance that cannot be broken down into simpler components by any non-nuclear chemical reaction

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#8
Viscosity :
a.the property of a fluid that resists the force tending to cause the fluid to flow.
b.the measure of the extent to which a fluid possesses this property

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The Periodic Table of elements:It have many elements in this chart

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#14
Group: An up and down column in the Periodic Table of Elements. These elements have similar properties like hardness, malleablility, etc.
Row: Elements in the Periodic Table of Elements that go from left to right. Elements in different rows have different numbers of valence electrons. The element on the right side has 8 valence electrons and is very stable (wont react). Metals are on the left side and non-metals on the right.

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#6
---Pure Substance: composed of a single material substances called pure, pure includes elemental and compound .
--- Element : Element refers to the type of atoms with the same nuclear charge number.
---Atom: Atom refers to the chemical reaction is divided into basic particle.
---Compound: Consists of two or more elements of pure.

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#11
Dalton:He think atom like a ball
Thomson:He thinks atom is                        chololate chip
Rutherford：He think the elecons are all around out side.

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George 10.Using the kinetic theory, explain what causes gas pressure.

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George 10.Using the kinetic theory, explain what causes gas pressure.

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There is a high pressure and a depression then ,the atmospheric pressure imbalance ,and then the air outside want to get to the high pressure ,and then they become energy and push inside that energy is gas pressure.

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＃5
melting point: Solid turn its physical state by solid state for the temperature of the liquid

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＃2

Flammability： Something easy to burning.

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each row in the table of elements. The number of electrons per period varies because the number of available track increases from energy level to energy level.

An classify of elements in columns, based on a set of properties that repeat from row to row

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#3
conductor of heat：The ability of heat to move easily.

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#15
The Atomic number is the number of protons in the atom. This is the number used in the Periodic Table of elements to put the elements in order.

#16
Metals: found on the left and center of the periodic table of elements. These elements are let heat/electricity move easily, sound bright, are shiny, and can bend easily.
Non-metals: these are found on the right side. They are the opposite of metals.
Metalloids: these are the elements in-between metals and non-metals. They can be like metals or non-metals. Sometimes they change with temperature.
Alkali metals: these are the metals on the left side. they are the most reactive.
Alkali earth metals. these are group two and make salt
Halogens: these are on the right side and are non-metals. They can also make salt and are reactive.
Noble gases: these are group 8 non-metals and very stable. All are gas at room temperature

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essay,1. Covalent  Bond： sharing of election.

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essay,1. Covalent  Bond： sharing of election.

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2.  Lonic  Bond :transfer of election.

Angela

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9.
Mass per unit volume
For example, the 5 kg/ m^3
Density means the per cubic meter is 5 KG

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Question 4
plastic
There is a strong toughness ，great malleability

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Isotopes are atoms of the same proton, such as H, D, T, they are isotopes, all have a proton, in fact, they are atoms, ions are charged particles, atoms are not charged

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proton: a positively charged elementary particle that is a fundamental constituent of all atomic nuclei.
Neutron: an elementary particle having no charge, mass slightly greater than that of a proton.
Electron: an elementary particle that is a fundamental constituent of matter