Take This Ultimate Year 8 Chemistry Test

1. What is an example of a Metal?

Carbon

Copper

Silicon

Neon

Silicon and Carbon are non-metallic solids, and Neon is a non-metallic gas.

Explanation

Silicon and Carbon are non-metallic solids, and Neon is a non-metallic gas.

2. The compound

is

Air

Water

Carbon dioxide

Oxygen

It is a chemical formula that represents a molecule of water, which is a fundamental and essential substance for life. Water contains 2 hydrogen atoms and one oxygen atom.

Explanation

It is a chemical formula that represents a molecule of water, which is a fundamental and essential substance for life. Water contains 2 hydrogen atoms and one oxygen atom.

3. Which one of these is a Non-metal?

Oxygen

Hydrogen

Neon

All of the above

Oxygen, hydrogen, and neon are all non-metals. Oxygen and hydrogen are gases at room temperature and are part of the non-metal category in the periodic table. Neon is a noble gas, which is a specific group of non-metals known for their lack of reactivity and inability to form many compounds.

Explanation

Oxygen, hydrogen, and neon are all non-metals. Oxygen and hydrogen are gases at room temperature and are part of the non-metal category in the periodic table. Neon is a noble gas, which is a specific group of non-metals known for their lack of reactivity and inability to form many compounds.

4. Which of the following pair is CORRECT?

Magnesium ---- Ma

Potassium ----- K

Sodium ------ So

Silicon ------ S

Magnesium ---- Mg
Potassium --- K (Kalium)
Sodium --- Na (Natrium)
Silicon ---- Si

Explanation

Magnesium ---- Mg
Potassium --- K (Kalium)
Sodium --- Na (Natrium)
Silicon ---- Si

5. The center of an atom is its

Nucleus

Proton

Neutron

Electron

An atom has 3 different subatomic particles known as protons, neutrons, and electrons. The protons and neutrons are found in the middle of the atom in the nucleus, and the nucleus is surrounded by electrons orbiting the nucleus.

Explanation

An atom has 3 different subatomic particles known as protons, neutrons, and electrons. The protons and neutrons are found in the middle of the atom in the nucleus, and the nucleus is surrounded by electrons orbiting the nucleus.

6. Which is the correct word equation for burning magnesium in the air?

Magnesium + magnesium oxide --- > oxygen

Magnesium + oxygen ---- > magnesium oxide

Magnesium oxide ---- > magnesium + oxygen

Magnesium ----- > oxygen + magnesium oxide

The reactants (starting or raw materials) are Magnesium and Oxygen in the air.
The products are Magnesium oxide - white ash, and the bright white light and heat energy.

Explanation

The reactants (starting or raw materials) are Magnesium and Oxygen in the air.
The products are Magnesium oxide - white ash, and the bright white light and heat energy.

7. When trying to identify a Non-metal, you should

Find the mass of the object.

See if the object has some of the opposite physical properties of a Metal.

Make sure that it is a good Conductor of heat, Bendable, and Shiny.

It must be in the gas state.

Non-metals have properties very different from Metals - many are the opposite.
They are brittle, not shiny, and poor conductors of heat and electricity.

Explanation

Non-metals have properties very different from Metals - many are the opposite.
They are brittle, not shiny, and poor conductors of heat and electricity.

8. What are some properties that an element is Metal?

It's shiny, soluble, and bendable.

It's flat, black, and a conductor of electricity.

It's shiny, bendable, and a good conductor of electricity.

It's shiny, brittle, and a good conductor of heat

The element exhibits metallic properties as it is shiny, indicating a reflective surface, bendable, signifying malleability, and functions as a good conductor of electricity, showcasing typical traits of metals. These characteristics align with the general properties observed in metallic elements within the periodic table.

Explanation

The element exhibits metallic properties as it is shiny, indicating a reflective surface, bendable, signifying malleability, and functions as a good conductor of electricity, showcasing typical traits of metals. These characteristics align with the general properties observed in metallic elements within the periodic table.

9. Which metal is not normally found as a pure substance in nature?

Sodium

Copper

Gold

Silver

Sodium is a very reactive metal that is normally combined with other elements to form compounds in nature - e.g., NaCl (salt). Copper, gold, and silver are less reactive than sodium and are typically found in nature as pure substances embedded into rocks.

Explanation

Sodium is a very reactive metal that is normally combined with other elements to form compounds in nature - e.g., NaCl (salt). Copper, gold, and silver are less reactive than sodium and are typically found in nature as pure substances embedded into rocks.

10. Which is not a correct description of an element?

Only one kind of atom

Pure substance

Can be found in the periodic table

Can be broken down into different substances

An element is a pure substance that consists of only one kind of atom. An atom can't be broken down into smaller particles (substances). There are 118 elements found in the periodic table.

Explanation

An element is a pure substance that consists of only one kind of atom. An atom can't be broken down into smaller particles (substances). There are 118 elements found in the periodic table.

11. A compound is a substance with

More than two atoms of the same element.

Two or more elements mixed together.

Only one element.

Two or more elements chemically combined

An atom is the smallest particle of a substance.
An element consists of only one kind of atom that can't be broken into other substances.
A compound is a substance made of two or more elements chemically combined.
A mixture is a substance made of two or more elements and/or compounds that can be separated by physical means.

Explanation

An atom is the smallest particle of a substance.
An element consists of only one kind of atom that can't be broken into other substances.
A compound is a substance made of two or more elements chemically combined.
A mixture is a substance made of two or more elements and/or compounds that can be separated by physical means.

12. Most atoms are made up of

Electrons, protons and neutrons

Empty space

Taken up space

None of the above

Most atoms are made up of three fundamental subatomic particles Electrons, protons and neutrons.

Explanation

Most atoms are made up of three fundamental subatomic particles Electrons, protons and neutrons.

13. Which of the following is not a pure form of the element CARBON?

Graphite

Charcoal

Diamond

Glass

The lead in a pencil is actually graphite - a form of carbon - it is not the metal Lead. Both diamond and charcoal are the same elements - carbon. Graphite, charcoal, and diamond, as well as soot and fullerenes, are carbon allotropes. Glass is made from sand that mainly contains silicon and oxygen as opposed to carbon.

Explanation

The lead in a pencil is actually graphite - a form of carbon - it is not the metal Lead. Both diamond and charcoal are the same elements - carbon. Graphite, charcoal, and diamond, as well as soot and fullerenes, are carbon allotropes. Glass is made from sand that mainly contains silicon and oxygen as opposed to carbon.

14. The following gases exist as molecules EXCEPT

Oxygen

Neon

Carbon dioxide

Nitrogen

A molecule is the smallest existing form of a chemical - it consists of 2 or more atoms of the same or different atoms bonded together. Oxygen exists as O2, nitrogen as N2, and carbon dioxide as CO2. Neon belongs to the last group of elements in the periodic table. It exists as a single atom instead of a molecule, and so do helium and argon.

Explanation

A molecule is the smallest existing form of a chemical - it consists of 2 or more atoms of the same or different atoms bonded together. Oxygen exists as O2, nitrogen as N2, and carbon dioxide as CO2. Neon belongs to the last group of elements in the periodic table. It exists as a single atom instead of a molecule, and so do helium and argon.

15. Sublimation is a process in which

A gas changes to a solid directly on heating

A solid changes to gas directly on heating

A liquid changes to gas on heating

A solid changes to a liquid and then to gas on heating

Sublimation is a process of changing the state in which a solid changes directly into gas on heating. Element iodine is a black crystal (but non-metal) that changes to a purple vapor on heating; there is no liquid iodine as such. Carbon dioxide (in the form of Dry Ice) also changes (sublimes) to a gas (carbon dioxide) directly at room temperature and pressure.

Explanation

Sublimation is a process of changing the state in which a solid changes directly into gas on heating. Element iodine is a black crystal (but non-metal) that changes to a purple vapor on heating; there is no liquid iodine as such. Carbon dioxide (in the form of Dry Ice) also changes (sublimes) to a gas (carbon dioxide) directly at room temperature and pressure.

16. A physical change has the following features:

New substances are formed; they can't be changed back (irreversible)

No new substances are formed; they can be changed back (reversible)

New substances are formed; they can be changed back (reversible)

No new substances are formed; they can't be changed back (irreversible)

A physical change normally involves a change in state and shape. It is usually reversible, and no new substances are formed. A chemical change (reaction) produces new substances and is normally irreversible.

Explanation

A physical change normally involves a change in state and shape. It is usually reversible, and no new substances are formed. A chemical change (reaction) produces new substances and is normally irreversible.

17. One piece of evidence for a chemical reaction is the formation of a precipitate. It is

A solid formed by mixing two solutions.

A gas formed by mixing two liquids.

A liquid formed by mixing two gases.

A solid formed by heating a liquid.

A precipitate is a solid that may be formed from mixing 2 solutions. A precipitate will often settle to the bottom of a reaction vessel after some time.

Explanation

A precipitate is a solid that may be formed from mixing 2 solutions. A precipitate will often settle to the bottom of a reaction vessel after some time.

18. Which gas is the lightest (lowest density)?

Oxygen

Carbon dioxide

Hydrogen

Helium

Hydrogen is the first element in the periodic table (with 1 proton, 1 electron, and no neutron), compared to Helium (the 2nd element) with 2 protons, 2 neutrons, and 2 electrons. Carbon dioxide is a gas made of Carbon and oxygen - it is denser than normal air, oxygen, hydrogen, and Helium.

Explanation

Hydrogen is the first element in the periodic table (with 1 proton, 1 electron, and no neutron), compared to Helium (the 2nd element) with 2 protons, 2 neutrons, and 2 electrons. Carbon dioxide is a gas made of Carbon and oxygen - it is denser than normal air, oxygen, hydrogen, and Helium.

19. Copper sulfate is a blue crystal with a formula of CuSO4. What is the total number of atoms in one molecule of this compound?

4

5

6

7

Explanation

20. Aluminum can be represented by

in the periodic table. Which of the following is INCORRECT?

The mass number is 27.

The neutron number is 14

The electron number is 13

The larger number is the mass number = protons + neutrons. The smaller number is the atomic number of an element = protons = electrons. So, the neutron number can be found by subtracting the protons from the mass number 27-23 = 14 neutrons

Explanation

The larger number is the mass number = protons + neutrons. The smaller number is the atomic number of an element = protons = electrons. So, the neutron number can be found by subtracting the protons from the mass number 27-23 = 14 neutrons