Science and Technology Basics Quiz

A full moon appears approximately 9 times brighter than a half moon to observers on Earth, despite having only twice the illuminated area. This is because lunar surface dust creates a opposition surge effect, making the full moon appear disproportionately brighter when sunlight reflects directly back at Earth.

Moonlight takes approximately 1.25 seconds to travel from the Moon to Earth, covering the average distance of 384,400 km at the speed of light. This slight delay means we always see the Moon as it was 1.25 seconds ago.

Chlorine gas (Cl2) has a distinctive greenish-yellow color, which makes it easily identifiable. This is why it was named after the Greek word 'chloros' meaning greenish-yellow. Neon, hydrogen, and krypton are colorless gases.

A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. It works by providing an alternative reaction pathway with lower activation energy, but remains unchanged after the reaction completes.

The pH scale measures acidity and alkalinity. A pH of 7 is neutral, below 7 indicates acidity, and above 7 indicates alkalinity (basic). The lower the pH below 7, the stronger the acid. This is a fundamental concept in acid-base chemistry.

The neutralization reaction occurs when an acid reacts with a base to produce a salt and water. The general equation is Acid + Base → Salt + Water. This is a fundamental type of chemical reaction where the acidic and basic properties cancel each other out.

Acids turn blue litmus paper red - this is a fundamental property of acidic solutions. The red color in litmus comes from a natural dye that changes structure in acidic environments. Acids do not change litmus to green or purple, and they never change red to blue.

Pencil lead is actually made of graphite, a form of carbon, not metallic lead. The misnomer comes from historical confusion when graphite was thought to be a form of lead. Carbon black is a pigment, plastic is used in pencil casings, and actual lead is toxic - none are used in pencil cores.

Exothermic reactions release heat energy into the surroundings - think "exit" for heat leaving the system. Endothermic reactions absorb heat. Heat is not liberated in all chemical reactions (some are endothermic), and substitution specifically refers to a reaction mechanism, not whether heat is released.

When dilute sulphuric acid reacts with zinc metal, hydrogen gas is evolved. This is a classic single displacement reaction producing zinc sulfate and hydrogen gas. Hydrogen peroxide (H2O2) is not produced, argon is inert, and sulfur dioxide would require different reactants/conditions.

Lemon juice is acidic due to the presence of citric acid. It has a pH around 2-3, well below 7 which indicates acidity. It is neither neutral (pH 7) nor basic (pH > 7), and it certainly isn't metallic.

Carbon dioxide dissolved under pressure creates the fizziness in carbonated drinks like Coke and Pepsi. When the bottle is opened, pressure decreases and CO2 comes out of solution as bubbles. Helium and hydrogen are much lighter gases that would escape, while oxygen doesn't create the characteristic fizz.

USB stands for Universal Serial Bus, an industry standard for cables, connectors, and communication protocols that connect computers to peripheral devices like keyboards, mice, and storage drives.

DNS configuration files on Linux use the full stop (.) as a critical delimiter in domain names and zone definitions. A missing full stop makes the server interpret fully qualified domain names incorrectly, causing resolution failures and configuration errors.

DDOS stands for Distributed Denial of Services, a cyber attack where multiple compromised systems flood a target with traffic, making it unavailable to legitimate users. It's a fundamental concept in cybersecurity and network security.

The ps command displays information about active processes running on the system. It shows a snapshot including process IDs (PIDs), terminal associations, CPU usage, memory consumption, and the command that launched each process.

NAT (Network Address Translation) is a method used in routers to remap IP addresses by modifying network address information in IP packet headers. It allows multiple devices on a local network to share a single public IP address when accessing the internet.

SELinux has three main modes: Enforcing (security policies are enforced and violations are blocked), Permissive (policies are checked but not enforced - only violations are logged), and Disabled (SELinux is turned off). 'General' is not a valid SELinux mode.

The uname command displays system information including the kernel version, system architecture, and operating system name. Despite having 'user' in its name, it does not display user account information - that's done by commands like 'whoami' or 'id'.

RPM (Redhat Package Manager) is a package management system used by Red Hat and its derivatives (Fedora, CentOS, etc.) for installing, managing, and removing software packages. It was originally developed by Red Hat for use in their Linux distributions.