Matter In Our Surroundings Archives

One day, Reena was helping her mother in household work. Suddenly a bottle from her mother’s cosmetics broke and the liquid fell on her hand. She got worried and asked her mother why she felt cold. Her mother explained the reason to her which satisfied her. Answer the following questions based on above passage. (𝒊) Can you guess the liquid that felt on Reena’s hand? (𝒊𝒊) Why did she feel cold when liquid fall on her hand? (𝒊𝒊𝒊) What are the values shown by Reena’s mother?

(𝑖) The liquid is nail paint remover which contains acetone. (𝑖𝑖) Acetone in nail paint remover is a volatile compound. It evaporates at a high rate and absorbs heat from…

Mrs. Khanna was making breakfast in kitchen. For this purpose she was heating water in a pan. In the meantime, her 12 years old son, Pappu entered the kitchen and saw the water vapour coming out from the pan. Pretend yourself to be Mrs. Khanna and answer the following questions: (𝒊) What is the process going on in the pan? (𝒊𝒊) Why was this process occurring? (𝒊𝒊𝒊) Give one way by which Pappu can relate this phenomenon with his everyday life. (𝒊𝒗) What values are shown by Pappu?

(i) Evaporation of water. (𝑖𝑖) The water absorbs heat from the burner and the water molecules keep changing their energies due to molecular collisions as a result of which some…

Water as ice has a cooling effect, whereas water as steam may cause severe burns. Explain these observations.

In case of ice, the water molecules have low energy while in case of steam the water molecules have high energy. The high energy of water molecules in steam is…

The temperature-time graph given alongside shows the heating curve for pure wax. From the graph answer the following: (a) What is the physical state of the substance at the point A, B, C and D? (b) What is the melting point of the substance? (c) What is the boiling point? (d) Which portions of the graph indicates that change to state is taking place? (e) Name the terms used for heat absorbed during change of states involved in above process.

(a) A-Solid state, B-Both solid and liquid status, C- liquid state, D-Both liquid and gaseous states (b) 15°C (c) 110°C (d) A1B1 and D1D2 (e) A1B1-Latent heat of fusion D1D2-Latent…

Name the changes in the terms of processes P, Q, R and S. (b) Which of the changes are exothermic and endothermic?

(a) ‘P’ is fusion (melting), ‘Q’ is boiling, ‘R’ is condensation and ‘S’ is sublimation. (b) ‘P’, ‘Q’ and ‘S’ are endothermic and ‘R’ is exothermic.

You are given the following substances with their melting and bowling points. Identify the physical status of X, Y and Z at room temperature (30°C).
Substance Melting point(°C) Boiling point(°C)
X -219 -183
Y 119 445
Z -15 78

‘X’ is gas at room temperature. ‘Y’ is solid at room temperature. ‘Z’ is liquid at room temperature.

A sample of water under study was found to boil at 102°C at normal temperature and pressure. Is the water pure? Will this water freeze at 0°C Comment.

Its freezing point will be below 0°C due to the presence od a non-volatile impurity in it.

A small volume of water in a kettle can fill a kitchen with steam’. Explain why.

The liquid form of water converts into gaseous from in steam. Its particles move very rapidly in the directions and fill the kitchen as gases completely fills the vessel.

The diagram below shows burning of an oil lamp. Draw the arrangement of particles of position ‘X’ and ‘Y’ when the lamp is burning.

Position (X) This is because oil is in liquid state. Position (Y) This is because oil burns to produce gaseous products.

Comment on the following statements Evaporation causes cooling. (b) Rate of evaporation of an aqueous solution decreases with increase in humidity. (c) Sponge though compressible is a solid. (d) Ice is solid at 0°C, while water is liquid at room temperature. (e) Sugar crystals dissolve faster in hot water than cold water.

(a) Evaporation produces cooling as the particles at the surface of the liquid gain energy from the surroundings and change into vapour, thereby producing a cooling effect. (b) Air around…

Substance	Melting point(°C)	Boiling point(°C)
X	-219	-183
Y	119	445
Z	-15	78

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