Respuesta :
1: What is the smallest part of a compound called?
mixture
element
atom
molecule
2: One molecule is made of two or more _____ bonded together.
nuclei
mixtures
atoms
compounds
3: Which of the following is a pure substance that can't be separated by physical means, and can't be decomposed into other substances by chemical means?
compound
molecule
mixture
element
4: A substance that cannot be separated physically is called a substance
heterogenous mixture
homogenous mixture
pure substance
mixed substance
5: Which term below represents a pure substance that can be separated chemically, but cannot be separated physically, that is made up of two or more different atoms?
mixture
element
molecule
chemical bond
6: Water is formed when two hydrogen atoms bond to an oxygen atom.
True
The hydrogen and the oxygen in this example are different __True_____________.
1) Answer is: molecule.
A chemical compound is a substance composed of many identical molecules.
Element bonded to an identical chemical element is not a compound.
For example, emerald (beryl) is chemical compound (beryllium aluminium cyclosilicate) with the chemical formula Be₃Al₂(SiO₃)₆. Pure beryl is colorless.
2) Answer is: atoms.
For example, polar molecule water (H₂O) is made of two hydrogen atoms and one oxygen atom connected with covalent bonds.
Other example, molecule carbon(IV) oxide (CO₂) is made of one carbon atom and two oxygen atoms bonded with covalent bonds.
Atom is the smallest constituent unit of matter that has the properties of a chemical element.
3) Answer is: element.
Pure substance is made of only one type of atom (element) or only one type of molecule, it has definite and constant composition with distinct chemical properties.
Compounds can be decomposed into other substances by chemical means, elements cannot.
There are 118 elements discovered so far.
4) Answer is: pure substance.
Pure substances can be separated chemically, not physically, that is difference between pure substances and mixtures.
For example, electrolysis of water (pure substance) is the chemical separation, because from one molecule (water) two molecules (hydrogen and oxygen) are produced. Water is separeted into two molecules:
Reaction of reduction at cathode: 2H⁺(aq) + 2e⁻ → H₂(g).
Reaction of oxidation at anode: 2H₂O(l) → O₂(g) + 4H⁺(aq) + 4e⁻.
5) Answer is: molecule.
A compound is a pure substance because its molecule cannot be broken down into simpler particles by physical means.
Molecule can be broken by chemical means (chemical reaction).
For example, balanced chemical reaction od decomposition of calcium carbonate:
CaCO₃(s) → CaO(s) + CO₂(g).
Calcium carbonate is made of calcium, carbon and oxygen atoms.
6) Answer is: atoms.
In water, atoms of hydrogen (H) and oxygen (O) are connected by polar covalent bonds.
Covalent bond is bond between nonmetals. Hydrogen and oxygen are nonmetals.
Oxygen is an element (nonmetal) with atomic number 8 (8 protons and 8 electrons). Oxygen can form anion (O²⁻) when it gain two electrons to have stable electron configuration like closest noble gas neon (Ne) with atomic number 10.
Electron configuration of oxygen atom: ₈O 1s² 2s² 2p⁴.
