What actually carries marks

58 topics, ranked by 4 real board papers (2023–2026). Nothing here is estimated — every figure is counted from the papers themselves.

#	Topic	Chapter	Asked	Marks	Weightage
1	Reflection of light by spherical mirrorshigh	Light — Reflection and Refraction	4/4	15	100
2	Combination and decomposition reactionshigh	Chemical Reactions and Equations	4/4	14	97
3	Heating effect of electric currenthigh	Electricity	4/4	14	97
4	The pH scale and why it matters in everyday lifehigh	Acids, Bases and Salts	4/4	12	92
5	Food chains and food webshigh	Our Environment	4/4	12	92
6	Fission and fragmentationhigh	How do Organisms Reproduce?	4/4	11	88
7	Coordination in plants: tropisms and plant hormoneshigh	Control and Coordination	4/4	10	87
8	Mendel's monohybrid crosshigh	Heredity	4/4	10	87
9	Ethanol and ethanoic acidhigh	Carbon and its Compounds	4/4	9	83
10	Physical properties of metals and non-metalshigh	Metals and Non-metals	4/4	8	81
11	Sexual reproduction in flowering plantshigh	How do Organisms Reproduce?	3/4	13	78
12	Nutrition in human beingshigh	Life Processes	4/4	6	76
13	Inherited traitshigh	Heredity	4/4	6	76
14	Defects of vision and their correctionhigh	The Human Eye and the Colourful World	4/4	6	76
15	The reactivity serieshigh	Metals and Non-metals	4/4	6	75
16	Magnetic field and field lineshigh	Magnetic Effects of Electric Current	4/4	6	75
17	Occurrence and extraction of metalshigh	Metals and Non-metals	3/4	10	72
18	How acids and bases react with metalshigh	Acids, Bases and Salts	4/4	4	71
19	Electric current and the electric circuithigh	Electricity	3/4	9	68
20	Autotrophic nutrition and photosynthesishigh	Life Processes	3/4	8	66
21	Respirationhigh	Life Processes	3/4	8	65
22	Force on a current-carrying conductor and Fleming's left-hand rulehigh	Magnetic Effects of Electric Current	3/4	8	65
23	Common salt and the chemicals made from ithigh	Acids, Bases and Salts	3/4	7	64
24	Dispersion of white light and the rainbowhigh	The Human Eye and the Colourful World	3/4	5	58
25	Transportation in human beingshigh	Life Processes	3/4	4	56
26	Transportation in plantshigh	Life Processes	3/4	4	56
27	Hormones in animalshigh	Control and Coordination	3/4	4	56
28	Magnetic field due to a current through a straight conductor	Magnetic Effects of Electric Current	3/4	4	56
29	Resistors in series	Electricity	3/4	3	53
30	Refraction of light, its laws and refractive index	Light — Reflection and Refraction	2/4	6	45
31	What the resistance of a conductor depends on	Electricity	2/4	6	45
32	Homologous series	Carbon and its Compounds	2/4	5	43
33	Naming carbon compounds	Carbon and its Compounds	2/4	5	43
34	Mirror formula and magnification	Light — Reflection and Refraction	2/4	5	43
35	Excretion in humans and plants	Life Processes	2/4	5	42
36	Oxidation and reduction	Chemical Reactions and Equations	2/4	4	41
37	Reflex action and the reflex arc	Control and Coordination	2/4	4	41
38	Domestic electric circuits	Magnetic Effects of Electric Current	2/4	4	41
39	Soaps and detergents	Carbon and its Compounds	2/4	4	39
40	Chemical equations and how to write them	Chemical Reactions and Equations	2/4	3	38
41	Managing the garbage we produce	Our Environment	2/4	3	38
42	The ozone layer and how it is being depleted	Our Environment	2/4	3	37
43	Balancing a chemical equation	Chemical Reactions and Equations	2/4	2	35
44	Water of crystallisation	Acids, Bases and Salts	2/4	2	35
45	Covalent bonding in carbon	Carbon and its Compounds	2/4	2	35
46	Sex determination in human beings	Heredity	2/4	2	35
47	Refraction by spherical lenses and image formation	Light — Reflection and Refraction	2/4	2	35
48	The human eye and power of accommodation	The Human Eye and the Colourful World	2/4	2	35
49	Lens formula and magnification	Light — Reflection and Refraction	1/4	5	27
50	Scattering of light and the Tyndall effect	The Human Eye and the Colourful World	1/4	3	23
51	Reproduction in human beings	How do Organisms Reproduce?	1/4	3	22
52	Reproductive health and contraception	How do Organisms Reproduce?	1/4	3	22
53	Ionic bonding and the properties of ionic compounds	Metals and Non-metals	1/4	2	20
54	Corrosion and how it is prevented	Metals and Non-metals	1/4	2	19
55	Ecosystem and its components	Our Environment	1/4	2	19
56	Acids, bases and indicators	Acids, Bases and Salts	1/4	1	18
57	The nervous system and how a neuron works	Control and Coordination	1/4	1	18
58	The human brain	Control and Coordination	1/4	1	18

Weightage is a relative index: the heaviest topic scores 100 and everything else is measured against it. A chapter’s figure on thechapter list is a different thing — its share of the paper’s 80 marks.