ENEM Natural Sciences Syllabus

Natural Sciences syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Natural Sciences in ENEM, not a summary of it.

1. 1

   Physics

   6 topics

   • Mechanics
   • Thermodynamics
   • Waves
   • Optics
   • Electricity and Magnetism
   • Modern Physics
2. 2

   Chemistry

   5 topics

   • General Chemistry
   • Organic Chemistry
   • Inorganic Chemistry
   • Physical Chemistry
   • Environmental Chemistry
3. 3

   Biology

   7 topics

   • Cell Biology
   • Genetics
   • Evolution
   • Ecology
   • Human Physiology
   • Botany
   • Zoology

Natural Sciences flashcards for ENEM

24 of 51 cards from the Natural Sciences deck — real questions with worked answers.

1. State Newton's second law of motion and give its equation.

   The net force on an object equals its mass times its acceleration: $\vec{F}_{net} = m\vec{a}$. Acceleration is directly proportional to net force and inversely proportional to mass.

2. What is the kinetic energy of a body of mass $m$ moving at speed $v$?

   $$E_k = \frac{1}{2}mv^{2}$$

3. Write the gravitational potential energy near Earth's surface and Newton's law of universal gravitation.

   Potential energy: $E_p = mgh$. Universal gravitation: $F = G\frac{m_1 m_2}{r^{2}}$, with $G \approx 6.67\times10^{-11}\ \mathrm{N\,m^2/kg^2}$.

4. Define linear momentum and state the impulse-momentum theorem.

   Momentum: $\vec{p} = m\vec{v}$. Impulse equals change in momentum: $\vec{J} = \vec{F}\,\Delta t = \Delta \vec{p}$. In an isolated system total momentum is conserved.

5. For uniformly accelerated motion, write the Torricelli equation relating velocity and displacement.

   $$v^{2} = v_0^{2} + 2a\,\Delta s$$ It links final velocity, initial velocity, acceleration, and displacement without needing time.

6. State the first law of thermodynamics.

   The change in a system's internal energy equals heat added minus work done by the system: $\Delta U = Q - W$. Energy is conserved.

7. Write the ideal gas law and name each variable.

   $$PV = nRT$$ where $P$ is pressure, $V$ volume, $n$ moles, $R \approx 8.31\ \mathrm{J/(mol\,K)}$ the gas constant, and $T$ absolute temperature in kelvin.

8. How do you convert a Celsius temperature to kelvin, and what is the sensible heat equation?

   $T(\mathrm{K}) = T(^{\circ}\mathrm{C}) + 273.15$. Sensible heat: $Q = mc\,\Delta T$, where $c$ is specific heat capacity.

9. State the second law of thermodynamics in terms of entropy.

   In any spontaneous process the total entropy of an isolated system never decreases: $\Delta S \geq 0$. Heat flows spontaneously from hot to cold, not the reverse.

10. Give the wave equation relating speed, frequency, and wavelength.

    $$v = \lambda f$$ where $v$ is wave speed, $\lambda$ wavelength, and $f$ frequency. Also $f = \frac{1}{T}$, with $T$ the period.

11. Distinguish transverse from longitudinal waves and give an example of each.

    In transverse waves oscillation is perpendicular to propagation (e.g., light, waves on a string). In longitudinal waves oscillation is parallel to propagation (e.g., sound).

12. What is the Doppler effect?

    The change in observed frequency of a wave when the source and observer move relative to each other: approaching raises the frequency, receding lowers it. It explains the changing pitch of a passing siren.

13. State Snell's law of refraction.

    $$n_1 \sin\theta_1 = n_2 \sin\theta_2$$ where $n$ is refractive index and $\theta$ the angle from the normal. Light bends toward the normal when entering a denser medium.

14. Write the thin-lens/mirror equation and the definition of refractive index.

    Lens/mirror equation: $\frac{1}{f} = \frac{1}{d_o} + \frac{1}{d_i}$. Refractive index: $n = \frac{c}{v}$, the ratio of light's speed in vacuum to its speed in the medium.

15. State the condition for total internal reflection and the critical-angle formula.

    It occurs when light travels from a denser to a less dense medium at an angle above the critical angle $\theta_c$, where $\sin\theta_c = \frac{n_2}{n_1}$ (with $n_1 > n_2$).

16. State Coulomb's law for the force between two point charges.

    $$F = k\frac{|q_1 q_2|}{r^{2}}$$ with $k \approx 9\times10^{9}\ \mathrm{N\,m^2/C^2}$. Like charges repel; opposite charges attract.

17. State Ohm's law and the electrical power equations.

    Ohm's law: $U = R\,i$ (voltage = resistance × current). Power: $P = U\,i = R\,i^{2} = \frac{U^{2}}{R}$.

18. How do total resistance formulas differ for series versus parallel resistors?

    Series: $R_{eq} = R_1 + R_2 + \cdots$. Parallel: $\frac{1}{R_{eq}} = \frac{1}{R_1} + \frac{1}{R_2} + \cdots$.

19. State the magnetic (Lorentz) force on a charge moving in a magnetic field.

    $$\vec{F} = q\vec{v} \times \vec{B}, \quad |F| = |q|\,v\,B\sin\theta$$ The force is maximal when velocity is perpendicular to the field and zero when parallel.

20. What is Faraday's law of electromagnetic induction?

    An induced EMF is generated by a changing magnetic flux: $\varepsilon = -\frac{d\Phi_B}{dt}$. The negative sign (Lenz's law) means the induced current opposes the flux change.

21. Write the photon energy relation and state the photoelectric effect.

    Photon energy: $E = hf = \frac{hc}{\lambda}$, with $h \approx 6.63\times10^{-34}\ \mathrm{J\,s}$. In the photoelectric effect, light above a threshold frequency ejects electrons from a metal, evidence that light is quantized.

22. State Einstein's mass-energy equivalence and De Broglie's wavelength.

    Mass-energy: $E = mc^{2}$. De Broglie wavelength of matter: $\lambda = \frac{h}{p} = \frac{h}{mv}$, showing particles have wave properties.

23. What distinguishes alpha, beta, and gamma radioactive decay?

    Alpha: emission of a helium nucleus $\ce{^4_2He}$ (mass number $-4$, atomic number $-2$). Beta: emission of an electron, converting a neutron to a proton (atomic number $+1$). Gamma: emission of high-energy photons with no change in mass or atomic number.

24. Define a mole and give Avogadro's number.

    A mole is the amount of substance containing as many entities as there are atoms in $12\ \mathrm{g}$ of carbon-12, namely Avogadro's number $N_A \approx 6.02\times10^{23}$ particles per mole.

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