Name That Force
What force pulls objects toward Earth?
Gravity
What are the two non-contact forces covered in this unit?
Gravity and magnetism
What force resists motion when two surfaces rub against each other?
Friction
When a chemical change occurs, what is formed?
One or more new substances
Ice melts into liquid water. Chemical or physical change?
Physical change
What force pushes upward on an object resting on a surface?
Normal force
True or False: A magnet must touch an object to exert a magnetic force on it.
False
Which would usually produce more friction: a smooth tile floor or carpet?
Name two types of evidence that may indicate a chemical change.
Any two: gas production, color change, temperature/thermal-energy change, precipitate formation
An apple slice turns brown after being cut. Chemical or physical change?
Chemical change
A student pushes a chair across the classroom. What type of force is the student's push?
Applied force
A magnet attracts a paper clip without touching it. What type of force is demonstrated?
Magnetic force / non-contact force
A toy car travels farther across tile than carpet. Why?
The tile has less friction.
Two clear liquids are mixed and a cloudy solid suddenly forms. What evidence of chemical change occurred?
A precipitate formed.
Sugar dissolves in tea. Does this provide strong evidence that a new substance formed?
No
A soccer ball rolls across grass and gradually slows down. What force causes it to slow down?
Friction
Two magnets are moved from 10 cm apart to 2 cm apart. What happens to the magnetic force?
It becomes stronger.
A rolling soccer ball eventually stops on the grass. Explain the role of friction.
Friction acts against the ball's motion and causes it to slow down and stop.
A clear yellow liquid becomes dark orange after another substance is added. What evidence suggests a chemical change?
Color change
An iron chair develops a rough, reddish-brown coating after sitting outside in the rain. What happened?
A chemical change occurred; rust formed as a new substance
A box is pushed to the right across the floor. Name the four main forces acting on the box and their directions.
Applied → right; Friction → left; Normal → up; Gravity → down
Magnet A is 3 cm from a metal object. Magnet B is 12 cm from the same type of object. Which magnet should exert the stronger magnetic force, and why?
Magnet A because magnetic force is stronger at a shorter distance.
A student rolls identical cars with the same starting force across carpet and smooth tile. Predict which car travels farther and explain why.
The car on tile travels farther because the tile produces less friction.
Two substances are mixed. The mixture begins bubbling and becomes warmer. Identify two pieces of evidence that a chemical change may have occurred.
Gas production and a change in thermal energy/temperature
Saltwater is heated until the water evaporates and salt crystals remain. Is this strong evidence of a chemical change? Explain.
No. It is a physical change; no new substance was formed.