Science Exam
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114 Terms
What is a pure substance?
A pure substance is a material made up of only one type of particle
Define element and compound.
An element is a pure substance made of only one type of atom
What is a homogeneous mixture?
A homogeneous mixture is a mixture in which the composition is uniform throughout. The different components are not visibly distinguishable (e.g.
What is a heterogeneous mixture?
A heterogeneous mixture is a mixture where the components remain distinct and can be visibly identified. Examples include salad or oil and water.
What is the difference between qualitative and quantitative observations?
Qualitative observations describe qualities using the senses (color
Define physical property.
A physical property is a characteristic of matter that can be observed or measured without changing its chemical identity. Examples include color
Define chemical property.
A chemical property describes a substance's ability to undergo changes that transform it into different substances. Examples include flammability and reactivity with acid.
What is a physical change?
A physical change affects the form of a substance but not its chemical composition. Examples include melting
What is a chemical change?
A chemical change results in the formation of one or more new substances with different properties. Indicators include color change
What is density and how do you calculate it?
Density is the mass of a substance per unit volume
How do you locate an element on the Periodic Table?
Elements are arranged by increasing atomic number; groups are vertical columns and periods are horizontal rows. The atomic number tells the number of protons in each atom.
What is the atomic number?
The atomic number is the number of protons in an atom's nucleus and defines the element. It is also equal to the number of electrons in a neutral atom.
What is the mass number?
The mass number is the total number of protons and neutrons in the nucleus of an atom. It helps determine the number of neutrons when subtracted from the atomic number.
Compare metals and non-metals.
Metals are shiny
Describe the alkali metals.
Alkali metals are found in Group 1
Describe the alkaline earth metals.
Found in Group 2
Describe the halogens.
Halogens are in Group 17 and are highly reactive non-metals. They form salts with metals and include fluorine and chlorine.
Describe the noble gases.
Noble gases are in Group 18 and are inert
Who proposed the first atomic theory and what was it?
John Dalton proposed that atoms are solid
What was Thomson’s atomic model?
Thomson proposed the “plum pudding” model where negatively charged electrons are embedded in a positively charged sphere. He discovered the electron using a cathode ray tube.
Describe Rutherford’s atomic model.
Rutherford discovered the nucleus using the gold foil experiment and proposed that atoms have a small
What did Bohr contribute to atomic theory?
Bohr proposed that electrons orbit the nucleus in fixed energy levels. His model explains how electrons can absorb or emit energy by jumping between levels.
What is standard atomic notation?
Standard atomic notation includes the element’s symbol
How do you calculate the number of neutrons in an atom?
Subtract the atomic number from the mass number: Neutrons = Mass Number - Atomic Number. This gives the number of uncharged particles in the nucleus.
What is the difference between atoms and ions?
Atoms are neutral with equal protons and electrons
How do you draw Bohr-Rutherford diagrams?
Show the nucleus with protons and neutrons
What is meant by “counting atoms”?
Counting atoms means identifying how many of each type of atom are in a chemical formula. For example
What is the test for oxygen gas?
A glowing splint relights in the presence of oxygen. This shows oxygen supports combustion.
What is the test for hydrogen gas?
A burning splint makes a “pop” sound when hydrogen gas is present. The sound indicates rapid combustion with oxygen.
What is the test for carbon dioxide?
Bubble the gas through limewater
How does static electricity form?
Static electricity occurs when electrons are transferred between objects due to friction
State the law of electric charges.
Like charges repel and opposite charges attract. This explains how static forces act between charged objects.
What is the difference between conductors and insulators?
Conductors allow electrons to flow easily (e.g.
Explain charging by friction.
When two different materials are rubbed together
What is conduction in charging?
Conduction transfers charge by direct contact between a charged and neutral object. The neutral object gains or loses electrons to become charged.
What is electric discharge?
Electric discharge is the sudden release of built-up static electricity
Draw and label a simple electric circuit.
A circuit includes a power source (battery)
What is electrical current (I)?
Current is the flow of electric charge
What is potential difference (voltage)?
Voltage is the energy per charge
What are four factors that affect resistance?
Resistance increases with longer wires
State Ohm’s Law.
Ohm’s Law is V = I × R
How do you calculate perfect efficiency?
Efficiency (%) = (Useful Output Energy/Input Energy) × 100. Perfect efficiency would be 100%
Compare series and parallel circuits.
Series circuits have one path for current; current is the same everywhere but resistance adds up. Parallel circuits have multiple paths
Give one analogy for series vs parallel circuits.
A series circuit is like a single-lane road—one blockage stops all flow. A parallel circuit is like a multi-lane highway—traffic keeps moving even if one lane is blocked.
What are renewable and non-renewable energy sources?
Renewable sources (e.g.
What are the four Earth spheres?
Biosphere (life)
Define biotic and abiotic factors.
Biotic factors are living (plants
Define individual
population
Compare photosynthesis and cellular respiration.
Photosynthesis converts CO₂ and water into glucose and oxygen using sunlight. Cellular respiration breaks glucose down to release energy
What are producers
consumers
What is the difference between food chains and food webs?
Food chains show one path of energy
Define herbivore
carnivore
What are ecological pyramids?
Diagrams that show relationships in ecosystems by energy (energy pyramid)
What are biotic and abiotic influences?
Biotic influences include predation and competition; abiotic influences include temperature
What is carrying capacity?
The maximum population size an ecosystem can support. Limited by resources and environmental conditions.
Compare primary and secondary succession.
Primary succession starts from bare rock (no soil)
Define ecological equilibrium.
A balanced state in which species and their environment remain relatively stable over time. Disturbances can disrupt this balance.
What is bioaccumulation?
The buildup of toxins in an organism over time. It can harm predators higher in the food chain.
What is biomagnification?
The increase in concentration of toxins at higher trophic levels. Top predators are most affected.
What are pesticides?
Chemicals used to kill pests that threaten crops. They can harm non-target species and pollute ecosystems.
How do human activities increase CO₂ levels?
Burning fossil fuels and deforestation release CO₂ into the atmosphere. This contributes to global warming and climate change.
What are celestial objects?
Natural objects in space like stars
What is the structure of the Sun?
The Sun has a core (nuclear fusion occurs)
What is nuclear fusion?
The process where hydrogen nuclei fuse to form helium
How do we measure space distances?
Use kilometers (km) for local space
What causes day and year on Earth?
Earth’s rotation causes day and night
What is the difference between heliocentric and geocentric models?
Heliocentric model has the Sun at the center; geocentric has Earth at the center. The heliocentric model is accepted based on scientific evidence.
What causes seasons?
Earth’s tilt causes different parts to receive varying sunlight during orbit. This leads to seasonal temperature changes.
What are solar and lunar eclipses?
A solar eclipse happens when the Moon blocks the Sun; a lunar eclipse occurs when Earth’s shadow covers the Moon. Eclipses depend on the alignment of Sun
What are constellations?
Patterns of stars recognized from Earth. They are used for navigation and storytelling in various cultures.
What is the Big Bang Theory?
A theory that the universe began as a single point and has been expanding ever since. Red shift and cosmic background radiation support it.
What is red shift?
A phenomenon where light from distant galaxies shifts to red wavelengths