Cells and Living Systems
What structure controls what enters and leaves a cell?
Cell membrane
What is the smallest unit of an element that retains its chemical identity?
An atom
What is the SI unit of force?
Newton (N)
What process changes liquid water into water vapor?
Evaporation
A thermometer reads 28°C. What instrument is being used and what is measured?
Thermometer; temperature in degrees Celsius.
Which organelle releases usable energy (ATP) during aerobic respiration?
Mitochondrion / mitochondria
What does a pH below 7 indicate?
An acidic solution
What force pulls objects toward Earth?
Gravity
What type of rock forms when molten rock cools and solidifies?
Igneous rock
Name one safety step when heating a test tube.
Wear goggles; point test tube away from people; use holder.
What is the main function of red blood cells?
Transport oxygen
What is the chemical formula for water?
H₂O
A cyclist travels 120 m in 20 s. What is the average speed?
6 m/s
What gas do plants take in for photosynthesis?
Carbon dioxide (CO₂)
A student measures 25 mL of water. Which apparatus is best for accurate volume measurement?
Graduated/measuring cylinder.
What process allows water to move across a partially permeable membrane?
Osmosis
What happens to atoms during a chemical reaction?
They are rearranged; atoms are conserved.
State Newton’s first law in everyday language.
An object stays at rest or moves at constant velocity unless acted on by an unbalanced force.
How can excess fertilizer cause fish deaths in lakes?
Nutrient runoff causes algal blooms; decomposition uses dissolved oxygen, leading to hypoxia.
A rock has mass 60 g and volume 20 cm³. Calculate density.
3 g/cm³
Explain why muscle cells generally contain more mitochondria than many other cells.
They need more ATP for muscle contraction, so they have more mitochondria to release energy.
A reaction produces bubbles and a temperature change. Give two pieces of evidence that a chemical reaction occurred.
Gas formation (bubbles) and temperature change.
A 4 kg object accelerates at 3 m/s². Calculate the net force.
12 N (F = ma = 4 × 3)
Explain one way planting vegetation helps reduce desertification or soil erosion.
Roots hold soil together and vegetation reduces wind/water erosion.
A student has reaction rates 8, 10, 9 mL/min. Calculate mean.
9 mL/min