makala Hamilton science review

chemical and physical chages

100

What is  physical change? Give two examples.

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. 

Examples: Ice melting into water, tearing a piece of paper.

200

How can you separate a mixture of sand and iron filings?

How can you separate a mixture of sand and iron filings?                                                                                                                                        Use a magnet to attract the iron filings, leaving the sand behind.

300

What happens when salt dissolves in water? Does this change its chemical composition?

What happens when salt dissolves in water? Does this change its chemical composition?

Salt dissolves in water by breaking into smaller particles (ions) that spread throughout the liquid.

No, the chemical composition of salt (NaCl) does not change; it is still salt, just mixed into the water.

400

Compare and contrast  How do mixing sand with water versus mixing salt with water. their physical changes differ? 

Compare and contrast mixing sand with water versus mixing salt with water. How do their physical changes differ?

When sand is mixed with water, it does not dissolve; instead, it settles at the bottom. This is a suspension.
When salt is mixed with water, it dissolves completely, forming a solution.

501

If you freeze water into ice and then melt it back into water, how do the properties of the substance change or stay the same?

If you freeze water into ice and then melt it back into water, how do the properties of the substance change or stay the same?

The state of matter changes (solid to liquid and back), but the chemical composition of H₂O remains the same.

electricity and magnestism

100

What is static electricity? What is human-harnessed electricity?

Static electricity is when electric charge builds up on something, like when you rub a balloon on your hair. Human-harnessed electricity is the kind we use in homes and buildings, coming from power plants and wires.

200

How do people use static electricity in real life? How do people use human-harnessed electricity?

Static electricity is used in printers and air purifiers. People use human-harnessed electricity to power homes, businesses, and technology like computers and phones.

300

imagine you are designing a new way to use electricity. Would you use static or human-harnessed electricity?

I would use human-harnessed electricity because it is more reliable and can power machines for a long time. Static electricity cannot provide steady energy, so it would not be good for running appliances.