Chemistry and Physics: Laws, Properties, and Examples

State the properties of solid state.

^{Ans: Solid has a definite shape, mass, and volume. The matter in its solid-state has the lowest amount of thermal energy as there is no space for the particles to move around. Solid tends to have a great electrical conductivity.}

What is a mixture? Give examples.

^{Ans: A mixture is a substance made by combining two or more different materials in such a way that no chemical reaction occurs. A mixture can usually be separated back into its original components. Some examples of mixtures are a tossed salad, salt water and a mixed bag of M&M's candy.}

What is solubility?

^{Ans: Solubility: The maximum amount of solute that can dissolve in a given amount of solvent. The maximum amount of a substance that can be dissolved in 100 grams of water at a given temperature is called its Solubility in water.}

State the properties of non-metallic elements.

^{ans: Physical properties of non-metals are:}

• ^{Non-metals are brittle.}
• ^{Non-metals are bad conductors of heat and electricity (except graphite).}
• ^{Non-metals are non-lustrous (dull) and cannot be polished (except iodine).}
• ^{Non-metals may be solids, liquids or gases at room temperature.}
• ^{Non-metals are neither tough nor strong.}

What is chemical change of matter? Give its two examples.

^{Ans: A chemical transition is the result of a chemical reaction, whereas a physical change is when the structure of matter changes, but not the chemical identity. Burning, cooking, rusting and rotting are examples of chemical changes.}

What is tincture of iodine? State its uses.

^{Ans: Uses of tincture of iodine: -It acts primarily as an antiseptic and can be applied on cuts, scrapes and acute wounds. -It is often added in water as disinfectant against microbes like bacteria and viruses but is not effective against protozoan parasites.}

What is chemical combination? What are laws of chemical combination?

^{Ans: Laws of Chemical Combination: Law of Conservation of Mass, Definite, Multiple Proportions, Gay Lussac's Law of Gaseous Volumes and Avagadro's Law. Chemistry usually involves chemical reactions where two or more elements combine to produce a single compound.}

Write the law of definite proportion, explain giving example,

^{Ans: The Law of Definite Proportions states that a chemical compound will always have the same proportions or amount of each element by weight, no matter what the amount is, or source. For instance, a 50-gram sample of carbon monoxide will have 21.5 g of carbon and 28.5 g of oxygen.}

What is a molecule of compound?

^{Ans: Molecules of compounds have atoms of two or more different elements. For example, water (H2O) has three atoms, two hydrogen (H) atoms and one oxygen (O) atom. Methane (CH4), a common greenhouse gas, has five atoms, one of carbon (C) and four of hydrogen (H, see Fig. 2.9).}

What is valency? State its importance.

^{Ans: The valency of an element is important because it determines how strong the bond between the atoms will be. The higher the valency, the stronger the bond. This is why elements with a high valency are often used in chemical reactions - they form strong bonds with other atoms.}

What is polyatomic ion? Give examples.

^{Ans: A polyatomic ion is a group of atoms carrying a charge (positive or negative). For example, nitrate ion (NO−3), hydroxide ion (OH - ).}

State the limitations of Thomson's model of the atom.

^{Ans: Thomson's atomic model failed to explain how the positive charge holds on the electrons inside the atom. It also failed to explain an atom's stability. The theory did not mention anything about the nucleus of an atom. It was unable to explain the scattering experiment of Rutherford.}

What are the features of Rutherford's model of an atom?

^{Ans: The model described the atom as a tiny, dense, positively charged core called a nucleus, in which nearly all the mass is concentrated, around which the light, negative constituents, called electrons, circulate at some distance, much like planets revolving around the Sun..}

Show the distribution of electrons in atoms of carbon and sodium.

^{Ans: Atomic number of carbon is 6 and atomic number of sodium is 11. So distribution of electrons in carbon atom is 6 = 2,4 Distribution of electrons in sodium atom is 11 = 2,8,1.}

What are isobar elements?

^{Ans: Isobar are elements that differ in chemical properties but have the same physical property. So, we can say that isobars are those elements that have a different atomic number but the same mass number. In contrast, Isotopes are those elements having the same atomic number and different mass numbers.}

What is atomic number and atomic mass? Explain.

^{Ans: Atomic mass is associated with the number of neutrons and protons that are present in a particular nucleus of an element. Atomic number is usually the number of protons present in an element's nucleus. It is the average weight of an element.}

State the characteristics of meristematic tissue.

^{Ans: Characteristics of Meristematic Tissue:}

• ^{The meristematic tissue has the quality of self-renewal. Every time the cell divides, one cell remains identical to the parent cell, and the others form specialized structures. They have very small and few vacuoles. The meristematic tissue is living and thin-walled.}

What is called parenchyma tissue? State its two characteristics.

^{Ans: Parenchyma Tissue. Parenchyma is a type of simple permanent tissue that makes a major part of ground tissues in plants, where other tissues like vascular tissues are embedded. They are non-vascular and composed of simple, living and undifferentiated cells, which are modified to perform various functions.}

Write a short note: Xylem tissues?

^{Ans; It is a type of complex tissue present in plants, that primarily transports water & nutrients from roots to stem and the leaves. They are responsible for providing mechanical strength to plants. Xylem is composed of four different kinds of elements: Tracheids, Vessels, Xylem Fibers, and Xylem Fibers.}

Give differences: Bone and Cartilage

^{Ans: Bones are the hard, inelastic and a tough organ that forms part of the vertebral skeleton. Cartilage is a soft, elastic and flexible connective tissue that protects the bone from rubbing against each other.}

Give differences: Velocity and Momentum.

^{Ans: The difference between momentum and velocity is that momentum is a measure of the amount of motion in an object, and velocity is a measure of an object's speed with direction. Momentum equals the mass of the object times its velocity, so velocity is one component of momentum.}

Give differences: Newton's first law of motion and Newton's second law of motion.

^{Ans: In the first law, an object will not change its motion unless a force acts on it. In the second law, the force on an object is equal to its mass times its acceleration. In the third law, when two objects interact, they apply forces to each other of equal magnitude and opposite direction.}

What is momentum? Write its formula and SI unit.

^{Ans: As mentioned above, the units of momentum will be the product of the units of mass and velocity. Mass is measured in kg and velocity in ms-1, therefore, the SI unit of momentum will be kgm/s(-1).}

Give scientific reason: The tyres of vehicles are made rough

^{Ans: If the tyres of automobiles were smooth, the friction produced would be minimal and thus, it would be difficult to stop or turn the automobile, increasing the risk of accidents. Hence, the tyres are grooved so as to increase the friction between the tyre and the surface of the road.}

Explain about balanced forces and unbalanced forces.

^{Ans: When the forces acting on an object have equal strength and act in opposite directions, they are balanced. These forces cancel out one another, and the motion of the object they are acting on remains unchanged. When the forces acting on an object are unbalanced, they do not cancel out one another.}

What is intertia? How many its types are there? Which are they?

^{Ans: Types of Inertia}

• ^{The inertia of rest: Tendency of a body to remain in the state of rest.}
• ^{The inertia of direction: Tendency of a body to remain in a particular direction.}
• ^{The inertia of motion: Tendency of a body to remain in a state of uniform motion.}

What is impulse of force? State its formula and SI Unit.

^{Ans: It is basically a change in momentum or impact of force. The S.I. unit of impulse is Newton-seconds (Ns) or kg m/s.}

State the common natural phenomena in which gravitational force is responsible.

^{Ans: Gravitational Force Examples:}

• ^{The revolving of the moon around the earth is due to gravitational attraction between them.}
• ^{The formation of tides in the ocean is due to the gravitational force acting between the earth and the moon.}

State the value of G calculated by Henry Cavendish. Why is G called universal constant?

^{Ans: Cavendish's result enabled the first calculation of the value of G. The value of G=6.673 X 10-11 N m2/kg2. G is also known as big G. Small g, the acceleration due to gravity at the surface of the Earth, has a value of 9.8 m/s2.}

Give scientific reason: