Properties of Matter
What do we call how a substances looks, feels, or behaves (such as color, texture, hardness)?
Physical properties
What type of change is tearing paper: physical or chemical?
Physical change
What is the main source of energy for almost all food chains on Earth?
The Sun.
What do we call organisms that break down dead material and return nutrients to the soil?
Decomposers (fungi, bacteria, some insects).
Name one of Earth’s major systems.
Possible answers: geosphere, hydrosphere, atmosphere, or biosphere.
Name two physical properties you could use to identify an unknown solid sample.
Name one sign that a chemical change has occurred.
Possible answers: color change, temperature change (heat released or absorbed), gas/bubbles produced, formation of a solid (precipitate), or a new smell.
What does the body use food energy for? Give two examples
For growth and repair; for movement and activity; to keep the body warm.
Give one way matter cycles between living things and the environment (example: water, carbon, nutrients).
Example: Plants take in carbon dioxide and water, make sugars; animals eat plants and return carbon through respiration; decomposers return carbon to the soil and air.
Give an example of how two Earth systems interact.
Possible answer: Rain (atmosphere) weathers rocks (geosphere) and provides water (hydrosphere) for plants (biosphere).
Explain the difference between mass and weight.
Mass is the amount of matter in an object; weight is the force caused by gravity on that mass. Mass stays the same, but weight can change if gravity changes.
Describe what happens at the particle level when a solid melts into a liquid.
Particles gain energy, vibrate more, move past each other, and become less fixed, allowing the solid to become a liquid.
Define producer and consumer in a food chain, and give one example of each.
Producer: makes its own food using sunlight (example: grass or a green plant). Consumer: eats other organisms (example: rabbit or fox).
Draw or describe a simple model showing how matter moves from plants to animals to decomposers.
Plants (producers) make matter (biomass) from air/water → herbivores eat plants and turn plant matter into animal biomass and waste → carnivores eat herbivores → when organisms die, decomposers break down bodies and waste, returning nutrients to soil for plants
How do weathering and erosion change the geosphere over time?
Weathering breaks rocks into smaller pieces; erosion moves those pieces away by wind, water, ice, or gravity, reshaping landforms over time.
A sample melts at 0°C and boils at 100°C at sea level. What is this substance likely to be, and which property helped you decide?
Likely water. The melting point and boiling point (physical properties) match pure water at sea level.
Give an example of a chemical change that involves energy being released as light or heat and explain why it is chemical.
Possible answer: burning wood (combustion) releases heat and light; it is chemical because new substances (ash, gases like CO2) form and chemical bonds change, releasing energy.
How is the energy stored in food originally captured by plants? (Name the process.)
Photosynthesis
Explain how removing a large number of top predators might change an ecosystem
Removing top predators can cause prey populations to increase, which may lead to overgrazing or overconsumption of plants. This can reduce plant populations, harm habitats, lower biodiversity, and change nutrient cycling and energy flow in the ecosystem.
Describe how living organisms (biosphere) can change the geosphere and give one specific example.
Organisms can break down rocks, build structures, or change soil composition. Example: Tree roots can break rock apart and create soil; coral reefs (organisms) build limestone structures that change seafloor shape.
Which property describes how much mass is packed into a given volume (mass per unit volume)?
Density
Explain conservation of mass in your own words for a reaction where two substances mix and form a new substance.
The total mass of the substances before the reaction equals the total mass after the reaction; atoms are rearranged but not created or destroyed.
A rabbit eats plants, and a hawk eats the rabbit. Explain how energy flows through this mini food chain and why the hawk gets less energy than the rabbit consumed from plants.
Energy flows from the Sun into plants (producers) via photosynthesis, then to the rabbit (primary consumer) when it eats plants, then to the hawk (secondary consumer) when it eats the rabbit. Energy is lost at each step (used for life processes and lost as heat), so the hawk receives less usable energy than the rabbit got from the plants.
If an area’s plant life is reduced by drought, predict at least two effects on the animals and decomposers in that area and explain why.
Effects: (1) Herbivore populations may decline due to less food, leading to fewer predators. (2) Decomposers may have less fresh plant material and leaf litter to break down, altering nutrient availability. Less plant cover can also increase soil erosion, affecting habitats.
A factory releases warm water into a river. Predict at least one likely effect on local aquatic life and explain your reasoning.
Possible effects: (1) Increased water temperature can stress or kill certain fish and aquatic organisms. (2) Warmer water may favor some species and harm others, changing the ecosystem balance and possibly greatly increase algae.