CBSE Class X – Science Chemistry Exam (Full Syllabus)

A physical change involves only change in physical state whereas a chemical change results in the formation of new substances. Boiling of water, melting of ice and dissolution of salt are physical changes as no new products are formed.

It is not atoms but the bonds between these atoms break and form during chemical reactions. Atoms of elements can rearrange but cannot change into other element.

The increasing order of acid strength is water < acetic acid < hydrochloride acid. Hydrochloride acid is a strong acid and ionises fully in water.

hydrogen-containing compound such as glucose is not categorized as acid because it does not produce hydrogen ions or some other ions, when dissolved in water, and consequently does not conduct electricity

Sodium carbonate (Na₂CO₃) is the salt of carbonic acid (H₂CO₂) and sodium hydroxide (NaOH). Here NaOH is a powerful base and carbonic acid is a weak acid.

Lime (CaO) is the base that reacts with a dilute acid such as HCl to form a salt called calcium chloride.

Elements having the same number of valence electrons belong to the Same group.

As we move from left to right in periodic table, metallic character decreases and non-metallic character increases. Here Na, Si, Cl, Mg, Al belong to same period.

Element  Y  has 1 less electron to complete its octet which is a property of nonmetals. On the other hand, element  Z  has 2 extra electrons to become stable which is a property of metals.

Denatured alcohol is the ethyl alcohol which has been made unfit for drinking purpose by adding small amount of poisonous substance like methanol, pyridine, etc.

Cyclobutane is a cyclic hydrocarbon consisting of four carbon atoms where each carbon atom is attached to the two other carbon atoms and two hydrogen atoms.

Metals generally do not show dullness. Metals such as gold and silver are usually shiny comparatively than dull.

Ionic compounds are generally soluble in water and insoluble in solvents such as kerosene and petrol.

When pieces of copper metal are kept immersed in silver sulphate solution for some time, the solution moderately becomes blue and a shiny greyish-white deposit of silver metal is formed on copper strip

HCl is a polar covalent compound and CCl₄  is a non-polar covalent compound. besides, sodium chloride (NaCl) and potassium chloride (KCl) form ionic compounds, as they consist of positive and negative ions.