Chemical and Physical Changes
Electricity and Magnestism
100
What is a physical change? Give two examples.
A physical change is a change in the form or appearance of a substance without changing its chemical composition.
100
What is an electromagnet?
An electromagnet is a type of magnet created by passing an electric current through a wire wrapped around a core, usually made of iron.
200
How can you separate a mixture of sand and iron filings?
Use a magnet to attract the iron filings, leaving the sand behind.
200
What is a permanent magnet?
A permanent magnet is a magnet that maintains its magnetic properties without needing an external electric current.
301
What happens when salt dissolves in water? Does this change its chemical composition?
No, the chemical composition of salt (NaCl) does not change; it is still salt, just mixed into the water.
301
Compare and contrast an electromagnet and a permanent magnet.
An electromagnet requires electricity to produce a magnetic field, while a permanent magnet has a constant magnetic field. Electromagnets can be turned on and off, while permanent magnets always attract certain metals.
402
Design an experiment to test how temperature affects the rate at which salt dissolves in water. What variables would you control, and how would you measure your results?
Prepare three beakers with the same amount of water at different temperatures (cold, room temperature, hot). Add an equal amount of salt to each and stir. Measure the time it takes for the salt to fully dissolve.
402
Using experimental evidence, explain why an electromagnet can be stronger than a regular magnet.
The strength of an electromagnet can be increased by adding more coils, increasing the electric current, or using a larger iron core. Experimental data would show that with more turns of wire, the magnetic field becomes stronger, making the electromagnet more powerful than many permanent magnets.
504
How can filtration and evaporation be used to separate a mixture of salt and water?
Evaporation can be used by heating the saltwater until the water evaporates, leaving the salt behind.
504
Based on evidence, why might an electromagnet be more useful in certain applications, such as a scrapyard crane?
An electromagnet can be turned on to pick up metal objects and turned off to drop them, which makes it more practical than a permanent magnet that is always attracting metal.