8th Grade Science - Chemical Interactions

The joining of atoms to form new substances is called ___________ _____________.
The atomic number is:

(Check all that apply.)
1. the number of protons in an atom
2. the number of neutrons in an atom
3. the number of electrons in an atom
4. none of the above
An electron in the outermost energy level in an atom is called a _____________ electron.
Atoms of the noble gases (group 18 of the Periodic Table) have ________ valence electrons.

( Check all that apply.)
1. 2 ( Helium)
2. 6
3. 8
4. 10
When atoms bond, the outermost energy level is filled
1. True
2. False
When electrons are transferred from one atom to another atom, an __________ bond is formed.
Ions that have more electrons than protons have a ___________ charge.
1. neutral
2. positive
3. negative
A ____________ bond forms when atoms share one or more pairs of electrons.
For a unit of a substance to be a molecule, it must:

(Check all that are required.)
1. keep all of the physical properties of that substance.
2. be composed of one and only one element.
3. consist of two or more atoms joined in a definite ratio.
4. keep all of the chemical properties of that substance.
A metallic bond is formed by the attraction between:

(Check all that apply.)
1. negatively charged metal ions
2. positively charged metal ions
3. the electrons around them
4. the protons around them
The properties of metals that are produced by metallic bonding include:

(Check all that apply.)
1. color
2. electrical conductivity
3. malleability
4. ductility
In a chemical reaction

(Check all that apply)
1. one or more substances are involved
2. a change takes place.
3. the same substances result.
4. one or more new substances are produced.
5. energy is never given off.
For a chemical reaction to take place, chemical bonds in the starting substances must break.
1. True
2. False
After a chemical reaction has taken place, the new substance

(Check all that apply.)
1. has different properties
2. has only changed physically
3. has formed new bonds
A __________ __________ is a combination of chemical symbols and numbers to represent a substance.
How many atoms are there in H₂ O ?
1. 2
2. 3
3. 4
4. 1
A __________ __________ is a representation that uses symbols and formulas to describe a chemical reaction.
In a chemical equation, the formulas to the right of the = are the:
1. reactants
2. products
According to the law of conservation of mass:
1. energy cannot be created or destroyed in ordinary chemical and physical changes.
2. mass cannot be created or destroyed in ordinary chemical and physical changes.
What is required for a balanced chemical equation?

(Check all that apply.)
1. The same numbers of atoms be on each side of the equation.
2. The same coefficients are on each side of the equation.
3. The mass of the left side must be greater than the mass of the right side of the equation.
4. The same kinds of atoms be on each side of the equation.
What coefficient should you add to the right side of the following equation in order to balance it?

2 Na + Cl₂ = NaCl
A chemical reaction in which two or more substances combine to form one new compound is called a ___________ reaction.
What type of reaction does the following chemical equation represent?NaCl + AgF = NaF + AgCl
1. synthesis reaction
2. decomposition reaction
3. single displacement reaction
4. double displacement reaction
Check which statement below are true:
1. Energy can be released in some chemical reactions.
2. Energy can be created in some chemical reactions.
3. Energy can be destroyed in some chemical reactions
4. Energy can be absorbed in some chemical reactions.
5. Energy can be changed from one form to another in some chemical reactions.
The smallest amount of energy required to start a chemical reaction is the ___________ energy.
As a catalyst speeds up a reaction, the substance that the catalyst is made of, changes.
1. Sometimes
2. Never
3. Always
A _____________ usually consists of two or more atoms of a substance joined in a definite ratio,
Covalent compounds are:
1. compounds that form when a group of atoms shares electrons.
2. compounds formed as the result of strong attractive forces between oppositely charged ions.
Check all the typical properties of Ionic compounds below:
1. brittle
2. low melting point
3. highly soluble
4. solutions that form can conduct electricity
You dissolve a compound in water and the number of hydronium ions increases. The compound is:
1. a base
2. an acid
3. neither
Check all the properties of a base below:
1. They increase the number of hydroxide ions when dissolved in water.
2. They have a sweet taste.
3. In solutions they can conduct electricity.
4. They never change color in an indicator.
5. The can be used to make soap.
A solution has a pH value of 12. The solution is:
When an acid neutralizes a base, what is produced?

(Check all that apply.)
1. salt
2. Helium
3. Nitrogen
4. water
What element must be present in any organic compound?
_______________ are biochemicals that are composed of one or more simple sugar molecules bonded together.
Proteins are composed of building blocks called ____________ acids.
The nucleic acid that is the genetic material of the cell is:
1. RNA
2. DNA
Check the statements below that are true about lipids:
1. Lipids dissolve in water.
2. Lipids are used to store excess energy in the body.
3. An organism can obtain energy by breaking down lipids.
4. Fat can never be important to good health.
5. Lipids can also be used to store some vitamins.
During the process of radioactivity or radioactive decay, and unstable nucleus gives off:

(Check any that apply.)
1. energy
2. water
3. air
4. particles
Energy in the form of light given off during alpha decay and beta decay from a nucleus is called __________ rays.
Which materials below would be useful for containing all forms of nuclear radiation?
1. concrete
2. wood
3. lead
4. water
5. air
If the human body is exposed to large doses of nuclear radiation, what can result?
1. fatigue
2. hair loss
3. cell damage
4. destruction of blood cells
5. all of the above
A ____________ is the amount of time it takes one-half of the nuclei of a radioactive isotope to decay.
The process by which a large nucleus splits into two small nuclei and releases energy is called nuclear ___________ .
A nuclear fusion reaction releases more energy per gram of fuel than a fission reaction does.
1. True
2. False