Chemistry

What are the main branches of chemistry?

* Organic Chemistry
* Inorganic Chemistry
* Physical Chemistry
* Biochemistry
* Analytical Chemistry

Why is polyacrylic acid polymer hydrophilic?

Polyacrylic acid polymer is hydrophilic because of the carboxylic acid groups (COOH) in the polymer, which can hydrogen-bond to water molecules.

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How are pure substances classified?

Pure substances are classified into elements and compounds.

What is an element?

An element is a pure substance that cannot be broken down into other substances by chemical means.

What is a compound?

A compound is a pure substance that is made up of two or more elements in fixed proportions.

What are mixtures?

Mixtures are two or more substances mixed together, which do not combine to form a new substance.

Name some elements.

* Aluminum
* Carbon
* Oxygen

Name some compounds.

* Aluminum Oxide
* Carbon Dioxide
* Water
* Salt

Name some homogeneous mixtures.

* Tap Water
* Petrol
* Air

Name some heterogeneous mixtures.

* Soil
* Granite
* Sewage
* Pizza

What are the methods used for separating liquid and solid mixtures?

Filtration and crystallization.

What is distillation used for?

Distillation is used to separate two liquids that are dissolved in each other.

What is chromatography used for?

Chromatography is an analytical technique used for the purification of mixtures of compounds.

What is a physical change?

physical change does not produce a new substance. Examples include melting, boiling, and dissolving.

What is a chemical change?

A chemical change results in the formation of a new substance, while the atoms are conserved. Examples include the burning of natural gas, which converts methane to CO2 and water.

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What is a nuclear change?

In a nuclear change, atoms are changed from one type to another.

What is the atomic number?

The atomic number is the number of protons in an atom.

What is the mass number?

The mass number is the number of protons and neutrons in an atom.

What is the nuclear model of an atom?

* It contains protons and neutrons.
* It has a positive charge equal to the number of protons.
* It is exceedingly small.
* It contains most of the atom's mass.
* It is exceptionally dense.

How do electrons behave in an atom?

* Electrons move through a relatively large volume of space.
* There is electrostatic attraction between the nucleus and electrons.
* The number of electrons equals the number of protons.

What is the atomic number?

* The atomic number is the number of protons in the nucleus.
* It defines the element.
* It equals the number of electrons in an uncharged atom.

What is the mass number?

* The mass number is the number of protons and neutrons in the nucleus.
* It is represented by A.
* It can be calculated as A = Z + N, where Z is the atomic number and N is the number of neutrons in the nucleus.

What are isotopes?

* Isotopes are identified as atoms of an element with the same number of protons but a different number of neutrons.
* For example, carbon has three isotopes: C-12, C-13, and C-14.

What is atomic weight?

* Atomic weight is the "weighted" average of the relative atomic masses of the various isotopes that occur naturally.
* For example, the atomic weight of copper can be calculated using the relative abundance of its isotopes.

How many elements are in the periodic table?

The periodic table consists of 118 elements.

What are the common group names in the periodic table?

* Group 1: Alkali metals.
* Group 2: Alkaline earth metals.
* Group 7: Halogens.
* Group 8: Noble (inert) gases.
* Lanthanides and actinides are also present in the periodic table.

How are electrons arranged in an atom?

* Electrons occupy principal energy levels (shells) identified by the principal quantum number (n) and denoted by the letters K, L, M, N.
* Each principal energy level can hold up to 2n^2 electrons.
* Within each principal energy level, there are n energy sublevels or sub-shells.
* Within each energy sublevel or sub-shell, electrons occupy orbitals (s, p, d, f).

How can electron configurations be determined?

* Electron configurations of elements can be determined using the following guidelines:


1. Electrons fill the lowest energy levels first.
2. Each orbital can hold only two electrons.
3. Electrons occupy orbitals in the same energy sublevel singly to the maximum extent possible and with their spins parallel.

What is the valence electron configuration?

Valence electron configuration refers to the outer principal energy level electron configuration for groups 1 to 8 of the periodic table.

What is the octet rule?

* The octet rule states that elements strive to achieve a stable electron configuration with eight valence electrons.
* Elements in Group 8 of the periodic table, known as noble gases or inert gases, are unreactive due to their stable electron configuration.

What are alkali metals?

* Alkali metals consist of Group 1A metals: Li, Na, K, Rb, Cs, Fr.
* They all have one valence electron in the outer s-orbital, which dominates their chemistry.

What are chemical equations used for?

Chemical equations are written to represent actual chemical reactions that occur.

What is the process for balancing chemical equations?

The process for balancing chemical equations includes writing the word equation, writing the individual formulas for each substance, balancing the number of atoms of each type by changing coefficients, checking the atoms balance, and writing the physical states for each reactant and product.

What do coefficients indicate in a chemical equation?

Coefficients indicate the relative numbers of particles of each substance involved in the reaction.

What are the physical states commonly represented in chemical equations?

The physical states commonly represented in chemical equations are Gas (g), Liquid (l), Solid (s), and Aqueous (aq).

What is Avogadro's number?

Avogadro's number is 6.02 x 10^23, which represents a very large number of particles.

What is the relationship between moles and mass?

The molar mass of a substance is equal to its relative atomic mass, and one mole of a substance has a mass equal to its molar mass.

How can you calculate the molar mass of a compound?

To calculate the molar mass of a compound, you need to write the formula of the molecule unit, determine the number of atoms of each individual element, obtain the atomic mass of each individual element from the periodic table, and calculate the overall molar mass as the sum of the constituent atomic masses.

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What is the formula for the number of moles?

The formula for the number of moles is n = m/M, where n represents the number of moles, m is the mass of the substance, and M is the molar mass of the substance.

How can you calculate the mass of a given number of moles of a substance?

The mass of a substance can be calculated by multiplying the number of moles (n) by the molar mass (M), using the formula m = n x M.

What is the general procedure for determining masses of substances involved in chemical reactions?

The general procedure includes writing the balanced chemical equation, converting the mass of the known substances into a number of moles using the equation n = m/M, determining the number of moles of the unknown substance using the number of moles of the known substance, and converting the number of moles for the unknown substance into a mass using the formula m = n x M.

What does the Kinetic Theory of Matter explain?

The differences between solids, liquids, and gases based on the way their individual particles are packed together.

How are the individual particles packed together in solids?

In solids, the individual particles are closely packed together and held together strongly.

How are the individual particles packed together in liquids?

In liquids, the individual particles are still held together fairly strongly but are able to slip past each other and change their relative positions.

How are the individual particles packed together in gases?

In gases, the individual particles are either very weak or negligible, and gases have no fixed shape and no fixed volume.

What does the Kinetic Theory of Gases state?

Gases consist of tiny particles in constant motion, moving in rapid, random, straight-line motion and colliding with one another and the container walls.

What causes the pressure of a gas in a container?

The pressure of a gas in a container is due to collisions of particles with the container walls.

Are gas collisions elastic or inelastic?

Gas collisions are perfectly elastic - there is no energy loss when gas particles collide with one another or the container walls.

What is the relationship between the average kinetic energy of gas particles and temperature?

The average kinetic energy of gas particles is proportional to the absolute (Kelvin) temperature.

How can the temperature of a gas be measured?

The temperature of a gas can be measured in degrees Celsius (°C) but is usually measured in Kelvin (K).

What is absolute zero on the Kelvin scale?

Absolute zero, 0 K, is equivalent to -273 °C.

In what units is pressure typically measured?

Pressure is typically measured in pascals (Pa), but kilopascals (kPa) are commonly used. Standard atmospheric pressure is 101.3 kPa.

What are the common units for measuring the volume of a gas?

The volume of a gas is usually expressed in liters (L), but it can also be expressed in cubic meters (m3), where 1 m3 = 1000 L.

What is Boyle's Law?

Boyle's Law states that for a fixed mass of gas at a constant temperature, the product of pressure and volume is constant (PV = constant).

What is Charles's Law?

Charles's Law states that the volume of a gas is directly proportional to its temperature in Kelvin, assuming constant pressure (V1/T1 = V2/T2).

What is the combined gas law?

The combined gas law combines Boyle's Law and Charles's Law to describe the relationship between pressure, volume, and temperature for a fixed amount of gas (P1V1/T1 = P2V2/T2).

What is Avogadro's Hypothesis?

Avogadro's Hypothesis states that equal volumes of all gases, measured under the same conditions of temperature and pressure, contain an equal number of molecules.

What is the Ideal Gas Law?

The Ideal Gas Law is applicable for any conditions of temperature, pressure, or number of moles and is expressed as PV = nRT, where P is pressure, V is volume, n is the number of moles, R is the gas constant, and T is temperature.

What is Dalton's Law of Partial Pressures?

Dalton's Law of Partial Pressures states that the total pressure in a mixture of non-reacting gases is equal to the sum of the partial pressures of each individual gas in the mixture.

What is the troposphere and why is it important?

The troposphere includes the Earth’s weather and most atmospheric pollution problems.

What is the stratosphere and why is it important?

The stratosphere is important because it contains ozone which protects the Earth’s surface from bombardment by high energy ultraviolet radiation.

Name the important gases in the troposphere.

The important gases in the troposphere are oxygen, hydrogen, nitrogen, and carbon dioxide.

What percentage of the atmosphere is made up of oxygen and why is it important?

Oxygen makes up about 21% of the atmosphere and is important in respiration in living things.

What is the percentage of hydrogen gas in the atmosphere?

Hydrogen gas constitutes less than 0.01% of the atmosphere.

What percentage of the atmosphere is made up of nitrogen and why is it important?

Nitrogen makes up about 78% of the atmosphere. Although nitrogen is relatively inert, nitrogen fixation is important in the formation of biomolecules such as amino acids and proteins.

What is ozone and how is it formed?

Ozone is an allotrope of oxygen, having the chemical formula O3. It is produced in the stratosphere by the interaction of ultraviolet radiation with O2 molecules.

How does ozone protect life on Earth?

Ozone protects life on Earth by absorbing harmful ultraviolet (UV) radiation from the sun. Once the ozone absorbs the UV rays, it is converted back into O2 molecules.

What is the Montreal Protocol and why was it established?

The Montreal Protocol is an international agreement in which industrialized countries agreed to phase out the use of chlorofluorocarbons (CFCs) as propellants by 1995. It was established to address the problem of ozone depletion.

What is the greenhouse effect?

The greenhouse effect is the phenomenon where carbon dioxide and water vapor in the atmosphere trap heat energy, leading to an elevation in the Earth's mean temperature.

What are the causes of increased carbon dioxide levels in the atmosphere?

Increased use of fossil fuels and the destruction of forests are the causes of increased carbon dioxide levels in the atmosphere.

Name some possible consequences of global warming.

Possible consequences of global warming include a temperature increase, increased rainfall, rising sea levels, poleward shift of climatic zones, more extreme weather events, and potential threats to some ecosystems.

What is photochemical smog and how is it formed?

Photochemical smog is formed when emissions from motor vehicles containing unburnt hydrocarbons and nitrogen oxides react with sunlight to form ozone and oxidized organic compounds, producing a brown haze.

What is acid rain and how is it formed?

Acid rain is formed when sulfur oxides, produced by the burning of sulfur-containing fossil fuels and roasting of sulfide ores, react with water in the atmosphere, forming acidic molecules such as sulfurous acid (H2SO3).

What are the consequences of acid rain?

Acid rain can damage forests, aquatic ecosystems, and buildings. It is a serious problem in parts of Europe and North America.

What is ionisation energy?

Ionisation energy is the energy needed to remove the most loosely bound electron from a gaseous atom or ion.

What is the first ionisation energy?

The first ionisation energy is the energy required to remove one electron from an atom.

What is the second ionisation energy?

The second ionisation energy is the amount of energy required to remove the next electron from the resultant ion.

What is electronegativity?

Electronegativity is a measure of an atom's electron-attracting ability.

How does electronegativity change across a period (row) of the Periodic Table?

Electronegativities of elements increase moving from left to right across a period.

What happens to electronegativity when moving down a group (column) of the Periodic Table?

Electronegativities decrease when moving down a group.

What are the types of solids?

The types of solids are metallic solids, ionic solids, covalent molecular solids, and covalent network solids.

What is metallic bonding?

Metallic bonding is the bonding between metals, characterized by a lattice of positive metal ions within a sea of delocalised electrons.

What are the properties of metallic solids?

Metallic solids are fairly dense, have high melting and boiling points, are malleable and ductile, and are good electrical conductors in solid or liquid states.

What is ionic bonding?

Ionic bonding is the bonding between metals and non-metals, involving electron transfer to form positively and negatively charged ions.

What are the properties of ionic solids?

Ionic solids are hard and brittle, have high melting and boiling points, are soluble in polar solvents, and are electrical conductors when molten or in aqueous solution.

What is covalent bonding?

Covalent bonding is the bonding between non-metals, characterized by electron sharing between atoms to produce a shared electron octet.

What are covalent network solids?

Covalent network solids are lattices of atoms joined by strong covalent bonds, and they are extremely hard and brittle with high melting and boiling points. They are usually insoluble in all solvents and electrical non-conductors.

What are covalent molecular solids?.

Covalent molecular solids are lattices of simple molecules, with strong covalent bonds within molecules and weak intermolecular forces between molecules. They are soft, waxy solids with low melting and boiling points and are often soluble in non-polar solvents. They are electrical non-conductors.

What are the four major types of intermolecular forces?

The four major types of intermolecular forces are dispersion forces, dipole-dipole forces, ion-dipole forces, and hydrogen bonding forces.

What is dipole moment?

Dipole moment is a measurement of the separation of two opposite electrical charges.

What are dispersion forces?

Dispersion forces are very weak intermolecular forces that exist between all molecules.

What are dipole-dipole forces?

Dipole-dipole forces occur when atoms form a covalent bond, but the electrons shared between them are not equally shared, resulting in a partial positive charge on one atom and a partial negative charge on the other. These partial charges create an attractive force between the two atoms.

What is an ion-dipole force?

An ion-dipole force refers to the attractive force between an ion and a molecule that has a dipole. The ion, which carries a positive or negative charge, interacts with the partial charges of the polar molecule, resulting in an electrostatic attraction.

What are hydrogen bonding forces?

Hydrogen bonding forces are a special type of dipole-dipole interaction that occurs between a hydrogen atom bonded to a highly electronegative atom (such as fluorine, nitrogen, or oxygen) and another electronegative atom nearby. The partially positive hydrogen atom is attracted to the partially negative atom, creating a strong and specific type of intermolecular bond.

What are the sloped regions in a heating and cooling curve?

The sloped regions represent temperature increasing and kinetic energy of particles increasing.

What are the horizontal regions in a heating and cooling curve?

The horizontal regions represent constant temperature and potential energy of particles increasing.

What are the characteristics of solids according to the Kinetic Theory of Matter?

1. Particles are closely packed.
2. Particles vibrate about fixed positions in a solid lattice.
3. Solids have fixed volumes and shapes.
4. The melting point of solids is the temperature at which they change to liquids.

What are the characteristics of liquids according to the Kinetic Theory of Matter?

1. Particles are close to one another, essentially in contact.
2. Particles are not in fixed positions.
3. Liquids have fixed volumes but variable shapes.
4. Some particles escape to the gaseous phase (vapor) and give rise to a vapor pressure.
5. Vapor pressure increases with an increase in temperature.
6. The boiling of a liquid (in an open container) is the temperature at which vapor pressure equals atmospheric pressure.

What is vapor pressure?

Vapor pressure is the pressure exerted by a vapor in equilibrium with the liquid from which it is derived. It increases with increasing temperature and is inversely related to the strength of the intermolecular forces in the liquid.

What is boiling?

Boiling is the change from a liquid to a gas at the boiling point, which is the temperature at which the vapor pressure of the liquid equals atmospheric pressure.