Science Answer the questions.[Che-2M]

1. Water and kerosene mixture can be separated by using a separating funnel because these are immiscible liquids and they have different densities.
2. Water and acetone mixture cannot be separated by by using a separating funnel because these are miscible liquids.

1. Burning of magnesium wire: Chemical change.

2. Freezing of water: Physical change.

3. Rusting of iron: Chemical change.

4. Glowing of electric bulb: Physical change.

• Physical change: Melting of candle wax, mixing of iron filings and sand, breaking a piece of chalk, cutting a piece of paper.

• Chemical change: Burning of candle wax, burning of wood, burning of piece of paper.

• Chemical change: Coal burning in air, making of cake.

• Physical change: A glass bottle breaking, wool beging knitted into a sweater.

1. Homogeneous mixtures: Those mixtures in which the substance are completely mixed together and are indistinguishable from one another, are called homogeneous mixtures.

Example: Sugar solution, copper sulphate solution.

2. Heterogeneous mixtures: Those mixtures in which the substances remain separate and one substance is spread throughout the other substance as small particles, droplets or bubbles, are called heterogeneous mixtures. 

Example: Starch solution, soap solution.

1. Pure substance made up of same kind of atoms.

Example: Sulphur.

2. Pure substance made up of same kind of molecules.

Example: Water.

• Metals: Iron and copper.
  
• Non-metals: Carbon and sulphur.
  
• Metalloids: Boron and silicon.
  

1. It shows the properties of its constituents, copper and zinc.
2. It has a variable composition.

• Similarity: In both the cases, the mixture can be separated into their constituents by physical methods.

• Difference: No separation is visible in the mixture of sugar and water whereas separation is visible in mixture of sand and sand.

• Physical change: Sublimation of solid, Formation of clouds, making of fruit salad from raw fruits, dissolving CO₂ in water.

• Chemical change: Decomposition of water into H₂ and O₂ by passing electric current.

• Two solid elements at room temp.– Iron and copper.

• Two liquid elements at room temp.– Mercury and bromine.

• Two gaseous elements at room temp.– Hydrogen and oxygen.

1. Water cannot be separated into its constituents, hydrogen and oxygen by physical methods.
2. Heat and light are given out when water is prepared by burning hydrogen in oxygen.

1. Solute: The substance which is dissolved in a liquid to make a solution is called as solute.

2. Solvent: The liquid in which solute is dissolved is known as solvent.

1. Malleability: Metals show this property but non-metals don’t.

2. Ductility: Metals show this property but non-metals don’t.

3. Electrical conductivity: Metals are good conductors of electricity whereas non-metals are bad conductors except graphite.

• Homogeneous mixtures: Soda water, air, vinegar, alcohol and water mixture, sugar and water mixture, Copper sulphate solution.

• Heterogeneous mixture: Wood, petrol and water mixture, chalk and water mixture.