Elements, Compounds, Formulas
Elements, Compounds, Formulas 100 — This is a pure substance made of only one type of atom.
Elements, Compounds, Formulas 100 — Element.
Physical vs Chemical Changes 100 — Chewing food changes its size and shape but not its identity. Is chewing a physical change or chemical change?
Physical vs Chemical Changes 100 — Physical change.
Solutions & Concentration 100 — The liquid in which a solute dissolves is called the ___.
Solutions & Concentration 100 — Solvent.
Motion, Distance & Speed 100 — Speed tells how fast something is moving. Speed equals this divided by this. (Use words.)
Motion, Distance & Speed 100 — Speed = distance ÷ time.
Forces & Newton’s Laws 100 — A force is a ___ or a ___. (Two words)
Forces & Newton’s Laws 100 — Push or pull.
200 — The chemical symbol for sodium is this two-letter code from the periodic table.
200 — NaNa.
200 — When stomach acid breaks down proteins into new substances, is that a physical or chemical change?
200 — Chemical change.
200 — A solution with only a small amount of solute compared to solvent is described as ___ (one word).
200 — Diluted.
200 — If a runner goes 300 meters in 60 seconds, what is the runner’s average speed in meters per second? (Show your calculation.)
200 — average speed=300 m60 s=5 m/saverage speed=60 s300 m=5 m/s.
200 — When forces on an object are equal in size and opposite in direction, they are called ___. What happens to the object’s motion in this case?
200 — Balanced forces; the object will stay at rest or continue moving at the same speed (no change).
300 — A substance made of two or more different elements chemically bonded is called a ___.
300 — Compound.
300 — Give one example from digestion of a physical change and one example of a chemical change.
300 — Example answers: Physical — chewing, mixing; Chemical — stomach acid breaking proteins, enzymes breaking food.
300 — What does it mean for a solution to be saturated?
300 — Saturated means it holds the maximum amount of solute that can dissolve at that temperature.
300 — On a distance–time graph, a straight diagonal line going up from left to right shows this kind of speed: constant, increasing, or decreasing?
300 — Constant speed.
300 — According to Newton’s First Law, an object at rest will stay at rest unless acted on by what kind of force?
300 — An unbalanced force.
400 — In the formula H2OH2O, the subscript tells how many of this atom are in the molecule. Which atom?
400 — Hydrogen (the HH in H2OH2O).
400 — Explain why mixing sugar into water is usually a physical change even though the sugar seems to disappear.
400 — Sugar dissolves into separate particles but its molecules are still the same; dissolving is a physical change because no new substance forms.
400 — Describe what a supersaturated solution is and give one sign that a solution might be supersaturated.
400 — Supersaturated contains more solute than normally possible; signs include crystals forming or undissolved particles settling.
400 — A car travels 150 kilometers in 3 hours, then 50 kilometers in 1 hour. What is the car’s average speed for the whole trip in km/h? (Show your calculation.)
400 — Total distance = 150+50=200 km150+50=200 km; total time = 3+1=4 h3+1=4 h; average speed =2004=50 km/h=4200=50 km/h.
400 — A ball moving in a circle at the same speed still has its motion changing. Why does this mean there is an unbalanced force acting on it?
400 — Even though speed is constant, direction is changing; acceleration (change in velocity) requires a net (unbalanced) force toward the center.
500 — Write the total number of atoms in the compound Ca(OH)2Ca(OH)2.
500 — Ca(OH)2Ca(OH)2 contains: 1 Ca, 2 O, 2 H → total atoms =10 1+2+2=5 1+2+2=5.
500 — A food turns brown and releases a new smell after being cooked. Is this likely a physical or chemical change? Explain briefly.
500 — Chemical change (new color and smell indicate new substances formed).
500 — If you add more solute and it settles to the bottom, how would you classify the solution: unsaturated, saturated, or supersaturated? Explain.
500 — Supersaturated if more solute than can stay dissolved; if added solute settles, often it’s past saturation.
500 — Explain how you can tell from a distance–time graph when an object is stopped.
500 — A horizontal (flat) line on a distance–time graph means the object is stopped (distance not changing over time).
500 — Two students push a box from opposite sides. Student A pushes with 10 N to the right; Student B pushes with 4 N to the left. What is the net force (include direction) and will the box speed up, slow down, or stay the same?
500 — Net force = 10 N (right)−4 N (left)=6 N to the right10 N (right)−4 N (left)=6 N to the right → box will speed up to the right.