Showing
110
question(s) for
UK Class 10
—
Subject:
Chemistry
Chemistry
Q1.
What is an element?
Answer:
An element is a substance made up of only one type of atom.
Chemistry
Q2.
What is an atom?
Answer:
An atom is the smallest part of an element that can exist.
Chemistry
Q3.
What is a compound?
Answer:
A compound is a substance formed when two or more different elements are chemically bonded together.
Chemistry
Q4.
What is a mixture?
Answer:
A mixture contains two or more substances that are not chemically bonded.
Chemistry
Q5.
What is a molecule?
Answer:
A molecule is a group of two or more atoms chemically bonded together.
Chemistry
Q6.
What is an isotope?
Answer:
Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons.
Chemistry
Q7.
What is the atomic number?
Answer:
The atomic number is the number of protons in the nucleus of an atom.
Chemistry
Q8.
What is mass number?
Answer:
Mass number is the total number of protons and neutrons in an atom.
Chemistry
Q9.
What is an ion?
Answer:
An ion is a charged particle formed when an atom or group of atoms gains or loses electrons.
Chemistry
Q10.
What is a positive ion?
Answer:
A positive ion is formed when an atom loses one or more electrons.
Chemistry
Q11.
What is a negative ion?
Answer:
A negative ion is formed when an atom gains one or more electrons.
Chemistry
Q12.
What is the periodic table?
Answer:
The periodic table is a systematic arrangement of chemical elements according to their atomic number and properties.
Chemistry
Q13.
What is a group in the periodic table?
Answer:
A group is a vertical column in the periodic table.
Chemistry
Q14.
What is a period in the periodic table?
Answer:
A period is a horizontal row in the periodic table.
Chemistry
Q15.
What are metals?
Answer:
Metals are elements that generally conduct heat and electricity and are often shiny, malleable and ductile.
Chemistry
Q16.
What are non-metals?
Answer:
Non-metals are elements that generally have poor electrical conductivity and may be dull or brittle when solid.
Chemistry
Q17.
What is a physical change?
Answer:
A physical change changes the form or state of a substance without forming a new substance.
Chemistry
Q18.
What is a chemical change?
Answer:
A chemical change produces one or more new substances with different chemical properties.
Chemistry
Q19.
What is a chemical reaction?
Answer:
A chemical reaction is a process in which reactants are converted into new substances called products.
Chemistry
Q20.
What are reactants?
Answer:
Reactants are the substances present at the start of a chemical reaction.
Chemistry
Q21.
What are products?
Answer:
Products are the new substances formed during a chemical reaction.
Chemistry
Q22.
What is conservation of mass?
Answer:
The law of conservation of mass states that mass is neither created nor destroyed during a chemical reaction.
Chemistry
Q23.
What is an exothermic reaction?
Answer:
An exothermic reaction releases energy to the surroundings, usually as heat.
Chemistry
Q24.
What is an endothermic reaction?
Answer:
An endothermic reaction absorbs energy from the surroundings.
Chemistry
Q25.
What is oxidation?
Answer:
Oxidation can involve the gain of oxygen, loss of hydrogen or loss of electrons.
Chemistry
Q26.
What is reduction?
Answer:
Reduction can involve the loss of oxygen, gain of hydrogen or gain of electrons.
Chemistry
Q27.
What is redox?
Answer:
A redox reaction is a reaction in which oxidation and reduction occur together.
Chemistry
Q28.
What is an acid?
Answer:
An acid is a substance that produces hydrogen ions in aqueous solution.
Chemistry
Q29.
What is an alkali?
Answer:
An alkali is a soluble base that produces hydroxide ions in aqueous solution.
Chemistry
Q30.
What is a base?
Answer:
A base is a substance that can neutralise an acid.
Chemistry
Q31.
What is neutralisation?
Answer:
Neutralisation is a reaction between an acid and a base that produces salt and water.
Chemistry
Q32.
What is the pH scale?
Answer:
The pH scale measures how acidic or alkaline an aqueous solution is.
Chemistry
Q33.
What does a pH below 7 indicate?
Answer:
A pH below 7 indicates an acidic solution.
Chemistry
Q34.
What does a pH of 7 indicate?
Answer:
A pH of 7 indicates a neutral solution at standard conditions.
Chemistry
Q35.
What does a pH above 7 indicate?
Answer:
A pH above 7 indicates an alkaline solution.
Chemistry
Q36.
What is an indicator?
Answer:
An indicator is a substance that changes colour depending on the acidity or alkalinity of a solution.
Chemistry
Q37.
What is litmus?
Answer:
Litmus is an indicator that turns red in acidic solutions and blue in alkaline solutions.
Chemistry
Q38.
What is a universal indicator?
Answer:
A universal indicator is a mixture of indicators that gives different colours across a range of pH values.
Chemistry
Q39.
What is a salt?
Answer:
A salt is an ionic compound formed when the hydrogen ions of an acid are replaced by metal ions or ammonium ions.
Chemistry
Q40.
What is electrolysis?
Answer:
Electrolysis is the decomposition of an ionic compound using electricity when it is molten or dissolved in water.
Chemistry
Q41.
What is an electrolyte?
Answer:
An electrolyte is a substance containing mobile ions that conducts electricity when molten or dissolved in water.
Chemistry
Q42.
What happens at the cathode during electrolysis?
Answer:
Positive ions move towards the cathode and gain electrons in reduction reactions.
Chemistry
Q43.
What happens at the anode during electrolysis?
Answer:
Negative ions move towards the anode and lose electrons in oxidation reactions.
Chemistry
Q44.
What is a catalyst?
Answer:
A catalyst increases the rate of a reaction without being used up overall.
Chemistry
Q45.
How does a catalyst increase reaction rate?
Answer:
A catalyst provides an alternative reaction pathway with a lower activation energy.
Chemistry
Q46.
What is activation energy?
Answer:
Activation energy is the minimum energy required for a reaction to occur.
Chemistry
Q47.
What factors affect the rate of a reaction?
Answer:
Temperature, concentration, pressure for gases, surface area and catalysts can affect reaction rate.
Chemistry
Q48.
How does temperature affect reaction rate?
Answer:
Increasing temperature usually increases reaction rate because particles move faster and collide more frequently with sufficient energy.
Chemistry
Q49.
How does concentration affect reaction rate?
Answer:
Increasing concentration usually increases reaction rate because there are more reactant particles per unit volume.
Chemistry
Q50.
How does surface area affect reaction rate?
Answer:
Increasing surface area usually increases reaction rate because more particles are exposed for collisions.
Chemistry
Q51.
What is collision theory?
Answer:
Collision theory states that particles must collide with sufficient energy and suitable orientation for a reaction to occur.
Chemistry
Q52.
What is a reversible reaction?
Answer:
A reversible reaction can proceed in both the forward and backward directions.
Chemistry
Q53.
What is dynamic equilibrium?
Answer:
Dynamic equilibrium occurs in a closed system when the forward and reverse reactions occur at equal rates.
Chemistry
Q54.
What is Le Chatelier's principle?
Answer:
It states that a system at equilibrium responds to a change in conditions by opposing the change.
Chemistry
Q55.
What is an ionic bond?
Answer:
An ionic bond is the strong electrostatic attraction between oppositely charged ions.
Chemistry
Q56.
What is covalent bonding?
Answer:
Covalent bonding involves the sharing of pairs of electrons between atoms.
Chemistry
Q57.
What is metallic bonding?
Answer:
Metallic bonding is the electrostatic attraction between positive metal ions and delocalised electrons.
Chemistry
Q58.
Why do ionic compounds have high melting points?
Answer:
Ionic compounds have strong electrostatic attractions between oppositely charged ions that require a lot of energy to overcome.
Chemistry
Q59.
Why do metals conduct electricity?
Answer:
Metals contain delocalised electrons that can move through the structure and carry electrical charge.
Chemistry
Q60.
Why do simple molecular substances have low boiling points?
Answer:
They have weak intermolecular forces that require relatively little energy to overcome.
Chemistry
Q61.
What is a giant covalent structure?
Answer:
It is a large structure in which atoms are joined by many strong covalent bonds.
Chemistry
Q62.
What is diamond?
Answer:
Diamond is a giant covalent form of carbon in which each carbon atom is bonded to four other carbon atoms.
Chemistry
Q63.
What is graphite?
Answer:
Graphite is a giant covalent form of carbon made of layers of carbon atoms with delocalised electrons.
Chemistry
Q64.
Why is diamond very hard?
Answer:
Each carbon atom is strongly covalently bonded to four other carbon atoms in a rigid three-dimensional structure.
Chemistry
Q65.
Why can graphite conduct electricity?
Answer:
Graphite has delocalised electrons that can move along its layers.
Chemistry
Q66.
What is crude oil?
Answer:
Crude oil is a mixture of hydrocarbons formed from the remains of ancient organisms over millions of years.
Chemistry
Q67.
What is a hydrocarbon?
Answer:
A hydrocarbon is a compound containing only carbon and hydrogen atoms.
Chemistry
Q68.
What is fractional distillation?
Answer:
Fractional distillation separates crude oil into fractions according to their different boiling points.
Chemistry
Q69.
What is an alkane?
Answer:
An alkane is a saturated hydrocarbon containing only single carbon-carbon bonds.
Chemistry
Q70.
What is the general formula of alkanes?
Answer:
The general formula for alkanes is CnH2n+2.
Chemistry
Q71.
What is an alkene?
Answer:
An alkene is an unsaturated hydrocarbon containing at least one carbon-carbon double bond.
Chemistry
Q72.
What is the general formula of alkenes?
Answer:
The general formula for alkenes with one double bond is CnH2n.
Chemistry
Q73.
How can an alkene be tested?
Answer:
An alkene can be tested using bromine water, which changes from orange to colourless.
Chemistry
Q74.
What is combustion?
Answer:
Combustion is a reaction in which a substance reacts with oxygen and releases energy.
Chemistry
Q75.
What are the products of complete combustion of a hydrocarbon?
Answer:
Complete combustion of a hydrocarbon produces carbon dioxide and water.
Chemistry
Q76.
What causes incomplete combustion?
Answer:
Incomplete combustion occurs when there is insufficient oxygen.
Chemistry
Q77.
Why is carbon monoxide dangerous?
Answer:
Carbon monoxide is poisonous because it reduces the blood's ability to carry oxygen.
Chemistry
Q78.
What is cracking?
Answer:
Cracking breaks long-chain hydrocarbons into smaller, more useful hydrocarbons.
Chemistry
Q79.
Why is cracking useful?
Answer:
Cracking produces shorter-chain alkanes for fuels and alkenes for making polymers.
Chemistry
Q80.
What is a polymer?
Answer:
A polymer is a very large molecule made from many repeating monomer units.
Chemistry
Q81.
What is a monomer?
Answer:
A monomer is a small molecule that can join with other monomers to form a polymer.
Chemistry
Q82.
What is addition polymerisation?
Answer:
Addition polymerisation joins unsaturated monomers together to form a polymer without producing another small molecule.
Chemistry
Q83.
What is a homologous series?
Answer:
A homologous series is a family of compounds with the same functional group and similar chemical properties.
Chemistry
Q84.
What is ethanol?
Answer:
Ethanol is an alcohol with the formula C2H5OH.
Chemistry
Q85.
How is ethanol produced by fermentation?
Answer:
Yeast converts glucose into ethanol and carbon dioxide under anaerobic conditions.
Chemistry
Q86.
What conditions are needed for fermentation?
Answer:
Fermentation requires yeast, a suitable temperature and the absence of oxygen.
Chemistry
Q87.
What is oxidation of ethanol?
Answer:
Ethanol can be oxidised to ethanoic acid, for example during the production of vinegar.
Chemistry
Q88.
What is ethanoic acid?
Answer:
Ethanoic acid is a carboxylic acid with the formula CH3COOH.
Chemistry
Q89.
What is an ester?
Answer:
An ester is an organic compound commonly formed when an alcohol reacts with a carboxylic acid.
Chemistry
Q90.
What is the general reaction between an alcohol and carboxylic acid?
Answer:
An alcohol reacts with a carboxylic acid to form an ester and water.
Chemistry
Q91.
What is a fertiliser?
Answer:
A fertiliser is a substance added to soil to provide essential mineral ions needed by plants.
Chemistry
Q92.
Why do plants need nitrates?
Answer:
Plants need nitrate ions to make amino acids and proteins for growth.
Chemistry
Q93.
What is potable water?
Answer:
Potable water is water that has been treated so that it is safe to drink.
Chemistry
Q94.
How can drinking water be obtained from fresh water?
Answer:
Fresh water can be treated by filtration and sterilisation to remove unwanted substances and microorganisms.
Chemistry
Q95.
What is filtration?
Answer:
Filtration separates an insoluble solid from a liquid using a filter.
Chemistry
Q96.
What is crystallisation?
Answer:
Crystallisation is used to obtain a soluble solid from a solution by forming crystals as the solvent is removed or the solution cools.
Chemistry
Q97.
What is chromatography?
Answer:
Chromatography separates substances in a mixture because they travel through a medium at different rates.
Chemistry
Q98.
What is the purpose of a chromatogram?
Answer:
A chromatogram shows the separated components of a mixture and can help identify substances.
Chemistry
Q99.
What is a pure substance?
Answer:
A pure substance contains only one element or one compound and has a fixed composition.
Chemistry
Q100.
How can purity be checked using melting point?
Answer:
A pure substance has a sharp melting point, while impurities usually cause melting to occur over a range and lower the melting point.
Chemistry
Q101.
What is relative formula mass?
Answer:
Relative formula mass is the sum of the relative atomic masses of all atoms shown in a chemical formula.
Chemistry
Q102.
What is the mole?
Answer:
A mole is the amount of substance containing approximately 6.02 × 10²³ particles.
Chemistry
Q103.
What is Avogadro's constant?
Answer:
Avogadro's constant is approximately 6.02 × 10²³ particles per mole.
Chemistry
Q104.
How is the number of moles calculated from mass?
Answer:
Number of moles equals mass in grams divided by relative formula mass.
Chemistry
Q105.
What is concentration?
Answer:
Concentration describes the amount of solute dissolved in a given volume of solution.
Chemistry
Q106.
What is the concentration formula in mol/dm³?
Answer:
Concentration equals the number of moles divided by the volume in dm³.
Chemistry
Q107.
What is percentage yield?
Answer:
Percentage yield compares the actual amount of product obtained with the theoretical maximum amount.
Chemistry
Q108.
Why can the percentage yield be less than 100 percent?
Answer:
Yield can be below 100 percent because reactions may be incomplete, products may be lost during separation, or side reactions may occur.
Chemistry
Q109.
What is atom economy?
Answer:
Atom economy measures how efficiently the atoms in the reactants are converted into the desired product.
Chemistry
Q110.
Why is high atom economy desirable?
Answer:
High atom economy reduces waste and makes chemical processes more efficient and sustainable.