physical and chemical changes

A copper penny turning greenish after a few years is an example of ...

• Chemical Change
• Physical Change

Which of the following is the common name for NaHCO₃

• Baking soda

• Lime water

• Vinegar

• Rust

Answer explanation

Baking soda ( sodium hydrogen carbonate or sodium bicarbonate)

Define atomic number.

• No. of neutrons in an atom

• No. of electrons or protons in an atom

• No. of atoms in an element

• No. of shells in an atom

Which of the following methods can be used to prevent rusting ?

• Painting

• Galvanisation

• Pouring water

• Alloy formation

Which of the following equation is correct ?

• 2 Mg+O₂ → CO_{2 + MgO}

• Fe+O2+H2O→Fe2O3

• MgO+ H2O → Mg+CO₂

In an atom, what is the number of protons equal to?

• the number of electrons
• the number of neutrons
• the number of molecules
• the number of nuclei

Which of the following is a negatively charged subatomic particle?

• Electron
• Proton
• Neutron
• Quark

Burning always indicates a

• Physical change

• Chemical change

• Periodic change

• Both physical and chemical change

Chemical formula for limewater

• CaCO₃

• CuSO₄

• CH₃COOH

• Ca(OH)₂

A chemical change may involve –

• change in colour

• change in temperature

• change in state of matter

• evolution of gas