7.6 Changes in Matter
How is a molecule of an element different from a molecule of a compound? Can you give an example of each?
A molecule of an element is made up of only one type of atom, while a molecule of a compound is made up of two or more different types of atoms chemically bonded together.
Element example: O₂ (Oxygen): This molecule consists of two oxygen atoms (O) bonded together. Since both atoms are the same, it’s a molecule of the element Oxygen.
Compound example: H₂O (Water): This molecule consists of two hydrogen atoms (H) and one oxygen atom (O) bonded together. Since it contains two different types of atoms (hydrogen and oxygen), it’s a molecule of the compound water.
What is the formula for calculating average speed?
Speed = Distance ÷ Time
What are the three methods of thermal energy transfer?
Conduction, Convection, Radiation
What is the main source of energy for our solar system, and where is it located?
The main source of energy for our solar system is the Sun. It is located at the center of the solar system and provides the heat and light that sustain life on Earth and influence the movement of the planets, moons, and other objects in the system.
What is fossil evidence, and how does it show that the Earth has changed over time?
Fossil evidence refers to the remains or traces of ancient organisms preserved in rocks, which can provide clues about the Earth's past environments, climates, and the types of life that existed at different times. Fossils are found in sedimentary rock layers, and studying them helps scientists understand how life on Earth has changed over millions of years.
If you see the chemical symbol NaCl, what do you think it represents? What does this tell you about the atoms that make up this substance?
The chemical symbol NaCl represents sodium chloride, which is commonly known as table salt.
This tells you that the substance NaCl is made up of two different types of atoms:
These two atoms are chemically bonded together to form the compound sodium chloride.
Sodium (Na) gives up an electron to become positively charged (Na⁺), and chlorine (Cl) accepts an electron to become negatively charged (Cl⁻), forming an ionic bond between them.
If a car travels 120 meters in 60 seconds, what is its average speed?
Use the formula: Speed = Distance ÷ Time
120 m divided by 60 s =
2m/s
Can you give an example of conduction in your everyday life?
Touching a metal spoon in a hot cup of soup transfers heat by conduction
What is the difference between a planet and a moon? Can you give an example of each?
The main difference between a planet and a moon is their orbit and what they orbit.
Planet: A planet is a large celestial body that orbits the Sun. Planets do not orbit other objects like moons do. They have their own gravitational pull that allows them to maintain their shape and orbit. Planets can be made of different materials (rocky or gaseous) and vary in size.
Moon: A moon is a natural satellite that orbits a planet (or sometimes a dwarf planet or asteroid). Moons are much smaller than planets and are often made of rock and ice. They are held in orbit by the gravity of the planet they orbit.
In summary, planets orbit the Sun, while moons orbit planets!
How do scientists use the theory of plate tectonics to explain changes in Earth’s surface?
Movement of Tectonic Plates
Formation of Mountains and Volcanoes
Earthquakes and Faults
Seafloor Spreading
Shifting Continents and Pangea
Ocean Basins and Trenches
The theory of plate tectonics explains that the Earth's surface is constantly changing due to the movement of tectonic plates. This movement leads to the formation of mountains, volcanoes, earthquakes, ocean basins, and the drifting of continents. Over time, these processes have dramatically reshaped the Earth's surface, and they continue to do so today.
How do you know how many atoms of each element are in a compound by looking at its chemical formula?
Identify the Elements
Look for Subscripts
Examples:
H₂O (Water):
CO₂ (Carbon Dioxide):
NaCl (Sodium Chloride):
What is the difference between speed and velocity?
Speed is how fast an object moves, while velocity includes both speed and direction.
What happens to the air near a radiator? How does this relate to convection?
Warm Air Rises: As the radiator warms the air nearby, that air becomes less dense and starts to rise because warm air is lighter than cooler air.
Cooler Air Moves In: As the warm air rises, cooler air from the room moves in to replace it, and the cycle continues. This creates a circulation of air in the room.
Convection Currents: The process described above, where warm air rises and cooler air moves in to take its place, is called convection. It’s the transfer of heat through a fluid (in this case, air) by the movement of the fluid itself.
Why do objects like comets, asteroids, and moons stay in orbit around the planets or the Sun?
Objects like comets, asteroids, and moons stay in orbit around the planets or the Sun because of the balance between two forces: gravity and inertia.
Gravity: The Sun (or a planet) exerts a gravitational pull on these objects, pulling them toward it. Gravity is the force that attracts objects with mass toward each other.
Inertia: Inertia is the tendency of an object to keep moving in a straight line at a constant speed unless acted upon by an outside force. When comets, asteroids, or moons are moving, their inertia wants to keep them traveling in a straight line.
The balance between gravity pulling the object toward the Sun (or a planet) and the object's inertia making it move in a straight line causes the object to follow a curved path, creating an orbit.
What are the three types of Rocks?
Igneous Rocks: Formed from the cooling and solidification of magma or lava. Examples include granite, basalt, and pumice.
Sedimentary Rocks: Formed from the accumulation and compaction of sediments, such as sand, mud, and organic material. Common examples are sandstone, limestone, and shale.
Metamorphic Rocks: Created when existing rocks (igneous, sedimentary, or other metamorphic rocks) are subjected to heat, pressure, or chemical processes that alter their structure or mineral composition. Examples include marble, and slate.
What is a physical change? Can you give an example of a physical change you’ve seen or experienced?
Cutting a piece of wood in half
Tearing a piece of paper
Crushing a Can
If an object travels 50 meters east and then 50 meters west, what is the distance and displacement?
(Hint: Distance is the total path traveled, while displacement is the straight-line distance between the starting and ending points, with direction.)
The object travels 50 meters east and then 50 meters west. So, the total distance traveled is:
Distance = 50 meters (east) + 50 meters (west) = 100 meters
If you place a metal rod in a fire, what type of thermal energy transfer is taking place?
Conduction is the transfer of heat through a material when particles collide with each other. In this case, the metal rod is directly in contact with the heat source (the fire). The heat from the fire is transferred to the metal rod through direct contact between the molecules in the metal.
If the Sun’s gravity suddenly disappeared, Earth and the other planets in the solar system would stop orbiting the Sun.
Earth's motion would change: Without the Sun's gravity pulling on Earth, Earth would no longer be kept in its elliptical orbit. Instead, Earth would continue moving in a straight line at the speed it was traveling at when the Sun's gravity disappeared. This is because of inertia — Earth's motion would carry it forward in a straight path, away from where the Sun used to be.
The other planets would do the same: All the planets would no longer orbit the Sun and would continue moving in straight lines at their current speeds. They would essentially "fly off" into space, no longer bound by the Sun’s gravitational pull.
Disruption of the solar system: The absence of the Sun’s gravity would cause chaos in the solar system. Planets, moons, comets, and asteroids would no longer follow their predictable orbits, and the whole structure of the solar system would fall apart.
What is a subduction zone?
Where one pate slides another plate.
Volcanoes and Trenches
What signs might indicate that a chemical change has taken place?
Color Change: If a substance changes color, it could be a sign of a chemical reaction. For example, when an apple turns brown after being cut, or when copper turns green as it rusts.
Formation of Gas: If bubbles or gas are produced (like when baking soda reacts with vinegar), this indicates a chemical change has occurred.
Temperature Change: A chemical change can produce heat (exothermic) or absorb heat (endothermic). For example, when wood burns, it releases heat.
Formation of a Precipitate: If two liquids are mixed and a solid forms at the bottom of the container, a chemical change has occurred. This is called a precipitate. An example is when you mix silver nitrate and sodium chloride, forming solid silver chloride.
Odor Change: A new smell can be released during a chemical change. For example, when food rots, a different odor is produced as a result of chemical reactions.
Light Emission: Some chemical reactions produce light. For example, fireworks or a glow stick gives off light as a result of chemical reactions.
A car travels 10 meters north in 5 seconds. What is its velocity?
2 m/s N
What is thermal equilibrium?
When two or more objects or systems in contact with each other reach the same temperature, and there is no net transfer of thermal energy between them.
In other words, when objects at different temperatures are placed in contact, heat will flow from the warmer object to the cooler one until both objects are at the same temperature. At that point, they have reached thermal equilibrium, and no further heat transfer occurs.
Can you explain why we don’t feel the Sun’s gravity pulling on us, even though it’s so powerful?
We don't feel the Sun's gravity pulling on us here on Earth because Earth is constantly in motion, orbiting around the Sun at a steady speed. Here’s why:
Earth's Orbit: Earth is moving sideways (or tangentially) around the Sun at a speed of about 30 kilometers per second (around 67,000 miles per hour). This fast motion keeps Earth from falling into the Sun. In other words, Earth's inertia (its tendency to keep moving in a straight line) balances the gravitational pull from the Sun, so instead of falling toward the Sun, Earth stays in orbit.
Gravity and Inertia Balance: The Sun's gravity pulls on everything in our solar system, including Earth, but Earth’s motion keeps it from getting pulled in. This creates a stable orbit where Earth continually falls toward the Sun, but because it's also moving forward at such a high speed, it keeps missing the Sun and stays in orbit around it.
We Feel Gravity from Earth, Not the Sun: While the Sun’s gravity is indeed very powerful, the gravity we feel is mainly from Earth. Earth’s gravity is what keeps us grounded on the surface, and that’s what we notice. The Sun's gravity acts on us as well, but it’s the same gravitational force acting on everything in the solar system, and we don’t feel it directly because we’re already being pulled toward Earth.
In summary, we don’t feel the Sun’s gravity because Earth is in a stable orbit around the Sun, where the Sun’s gravity pulls us toward it, but Earth’s motion keeps us from falling into the Sun. The gravity we experience is Earth's, which is what keeps us anchored to the ground.
What are the three boundaries?
Convergent:
Divergent:
Transform: