Chemical and Physical Changes
Melting ice into water is what kind of change?
Physical change
What force pulls objects toward Earth’s center?
Gravity
What is the net force if 10 N pulls right and 10 N pulls left?
0 N (balanced)
What is the formula for speed?
Speed = Distance ÷ Time
How is velocity different from speed?
Velocity includes direction
Burning wood is what kind of change?
Chemical change
What force slows objects as they fall through air?
Air resistance
15 N right and 10 N left — net force and direction?
5 N right
A car travels 100 m in 10 s. What’s its average speed?
10 m/s
What does “displacement” mean?
Distance and direction from start to end
What evidence shows a chemical change has occurred?
Color change, gas formation, light, temperature change, bubbles, precipitate, odor, rusting, or rotting.
CITY GIRLS LIKE THEIR BIG ORANGE PANTS BECAUSE ROCKETS RULE
If two objects fall, one heavy and one light, which will hit the ground first (ignoring air)?
They fall at the same rate
What kind of force causes a change in motion?
Unbalanced force
On a distance-time graph, what does a flat line mean?
The object is not moving
A car travels 5 km north and 5 km south — what’s its displacement?
0 km
Why is dissolving sugar in water considered a physical change?
Because no new substance is formed
What happens to air resistance as an object’s speed increases?
It increases
A soccer ball at rest is kicked—what kind of forces act?
Unbalanced
On a distance-time graph, what does a steeper line mean?
Faster speed
If an object changes direction but keeps the same speed, does its velocity change?
Yes
When metal rusts, what causes that chemical change?
Reaction with oxygen in the air
Why does a feather fall slower than a rock on Earth but not on the Moon?
Air resistance on Earth slows the feather; no air on the Moon
If a 20 N force up and 30 N force down act on an object, what’s the net force and direction?
10 N down
If two objects’ lines cross on a graph, what does that mean?
They’re at the same position at that time
What two things can change an object’s velocity?
Speed or direction (or both)