Science Grade 8 Question Preview (ID: 42781)

Science Grade 8. TEACHERS: click here for quick copy question ID numbers.

Define Electrons
a) They are the smallest of the sub-atomic particles
b) 2000 times smaller than protons and neutrons
c) They move around the atomic nucleus
d) All

Define Pure Substance
a) Compound mixture
b) Two classes namely elements and compounds
c) Both elements and compounds of an atom
d) None

Elements are made up of
a) Atoms of a mixture
b) Atoms of the same kind
c) Atoms of the same size
d) None

Compounds are made up of
a) None
b) One kind of atom in a fixed ratio
c) Two or more kinds of atoms in a scattered ratio
d) Two or more kinds of atoms in a fixed ratio

What are molecules
a) Two or more atoms that are CHEMICALLY bonded together
b) 1 atom makes up a molecule
c) Two or more atoms that are PURELY bond together
d) All

An Atom in a molecule can be of the same kind
a) False
b) True
c) None
d) Maybe

Molecule of the same kind is called a
a) Mixture of elements
b) Mixture of compounds
c) Molecule of an element
d) None

Molecule of the different kind is called a
a) Mixture of element and compound
b) Molecule of compound
c) Element
d) None

Do all elements have molecules
a) No
b) Yes
c) Maybe
d) None

What are diatomic molecules
a) None metals on the right side of the Periodic table
b) are gases at room tempreature
c) that exist as molecules made up of two atoms each
d) All

How are Atoms in a molecule held together
a) A force of energy
b) A special force called chemical bond
c) A force of light and darkness
d) None

What is the chemical formula for Water
a) H2O
b) H2O which means Hydrogen is 2 atoms and Oxygen is 1 atom
c) All
d) None

What does the 2 stand for in H2O?
a) The 2 is a subscript which tells us there are 2 H ATOMS
b) The O does not have a subscript
c) All
d) None

Hydrogen peroxide has a boiling point of
a) 120 degrees cel
b) 150 degrees cel
c) 100 degrees cel
d) None

What is the chemical formula for Hydrogen Perxoide
a) H2O
b) H2O2
c) HO
d) None

What are chemical bonds
a) Atoms combined because they experience an attractive force
b) Forces that hold atoms together
c) All
d) None

What is it called when atoms separate from each other
a) Chemical reaction
b) They recombine into different combinations
c) All
d) None

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