Science 10 - Unit A Test - Energy and Matter in Chemical Changes

Match the following symbols with their meanings under WHMIS.

• Symbol for substances that can catch fire easily

• 
• Symbol for infectious materials that can cause diseases

• 
• Symbol for substances that can cause serious health effects

• 
• Symbol for substances that can cause skin burns or damage metals

• 

Match the following symbols with their meanings under WHMIS.

• Symbol for substances that can cause skin burns or damage metals

• Corrosive

• Symbol for infectious materials that can cause diseases

• Biohazardous

• Symbol for substances that can catch fire easily

• Toxic

• Symbol for substances that can cause serious health effects

• Flammable

(a)   first introduced the concept of a dense positive nucleus in their atomic model.

• Thompson

• Rutherford

• Bohr

• Dalton

Answer explanation

Rutherford first introduced the concept of a dense positive nucleus in his atomic model, which was a significant advancement over previous models, such as Dalton's and Thompson's.

Elements in the same group of the periodic table have similar:

• Atomic masses

• Numbers of protons

• Valence electrons

• Electron shells

Answer explanation

Elements in the same group of the periodic table have similar valence electrons, which determine their chemical properties. This is why they exhibit similar reactivity and bonding behavior.

An (a)   bond is formed when electrons are transferred between a metal and a non-metal.

• Ionic bond

• Covalent bond

• Metallic bond

• Hydrogen bond

Answer explanation

An ionic bond is formed when electrons are transferred from a metal to a non-metal, resulting in the formation of charged ions that attract each other. This distinguishes it from covalent, metallic, and hydrogen bonds.

What is the pH value of a neutral solution?

• 0

• 7

• 14

• 5

Answer explanation

The pH scale ranges from 0 to 14, where 7 is considered neutral. Values below 7 indicate acidity, while values above 7 indicate alkalinity. Therefore, the pH value of a neutral solution is 7.

The reaction (a)   is an example of a combustion reaction.

• 2H₂ + O₂ → 2H₂O
• NaCl → Na + Cl₂
• CH₄ + 2O₂ → CO₂ + 2H₂O
• AgNO₃ + NaCl → AgCl + NaNO₃

Answer explanation

The reaction CH₄ + 2O₂ → CO₂ + 2H₂O is a combustion reaction, where methane (CH₄) reacts with oxygen (O₂) to produce carbon dioxide (CO₂) and water (H₂O), releasing energy.

Elements in the same group of the periodic table share similar properties because they have

• the same atomic mass

• the same number of protons

• the same number of valence electrons

• the same electron configuration

Answer explanation

Elements in the same group of the periodic table have the same number of valence electrons, which determines their chemical properties and reactivity. This is why they share similar characteristics.

Match the following terms with their descriptions:

• A substance that donates protons or accepts electrons

• Homogeneous mixture

• A chemical reaction where two compounds exchange ions

• Double Replacement Reaction

• A chemical bond formed by the sharing of electron pairs

• Acid

• A mixture that has a uniform composition throughout

• Isotopes

• Elements with the same number of protons but different numbers of neutrons

• Covalent bond

Answer explanation

Isotopes are elements that have the same number of protons but different numbers of neutrons. This matches the description given in the question, distinguishing them from the other terms listed.

Match the following types of chemical reactions with their descriptions.

• A reaction where an element replaces another in a compound.

• Combustion

• A reaction where a substance combines with oxygen, releasing energy.

• Decomposition

• A reaction where a compound breaks down into simpler substances.

• Double Replacement

• A reaction where parts of two compounds exchange places.

• Single Replacement

Answer explanation

A Single Replacement reaction occurs when one element replaces another in a compound. This distinguishes it from Decomposition (breaking down), Double Replacement (exchange between two compounds), and Combustion (reaction with oxygen).